Category: Sciences 2502

Streptomyces Bacteria: Overview

Belonging to the actinomycete family (Aigle & Corre 2012), streptomyces bacteria have a very peculiar morphology (Jani et al. 2015). Among the key species that comprise the streptomyces bacteria population, Streptomyces coelicolor, Streptomyces ambofaciens (Laureti et al. 2011), Streptomyces lividans, Streptomyces albicans, Streptomyces griseus and Streptomyces plicatosporus (Qi et al. 2014) must be mentioned. The colony shape can be identified as circular (Slama et al. 2015), its elevation being traditionally described as raised (Bhave et al. 2013) and its margins being entire for the most part (Lv et al. 2013). The size of a colony usually ranges from minicompartments (f <0.7 µm) to long compartments (23 µm) (Flärdh & Buttner 2009).

The bacteria are aerobic and gram-positive (Taichi et al. 2013). Streptomyces are characterized by the rather complex structure of aerial hyphae 0.52.0 µm long (Bhave et al. 2013), which are capable of forming layers and differentiating into a chain of spores afterward (Duong et al. 2012). As far as the specific properties of the bacteria in question are concerned, their ability to produce bioactive secondary metabolites, including antifungals, antivirals, antitumorals, anti-hypertensives, immunosuppressants (Procopio et al. 2912, p. 466) deserves to be mentioned. The specified property is triggered by Sortase activity (Duong et al. 2012). The aerial mass color of Streptomyces incorporates the following color series: gray (Gy), white (W), red (R), yellow (Y), green (Gn), blue (Bl), and violet (V) (Tadei, Rodriguez, Márquez-Vilchez & Castelli 2006, p. 222). The substrate mycelium, in its turn, is characterized by the colors of beige (Bg), black (Bck), blue (Bl), biscuit (Bs), brown (Bw), ivory (Iv), olive (Ol), orange (Or), purple (P), pink (Pk), red (R), red-violet (R-V), tan (T), violet-purple (V-P), yellow (Y), yellow-greenish (Y-Gr) (Tadei, Rodriguez, Márquez-Vilchez & Castelli 2006, p. 222). Streptomyces produce melanoid pigments and has a spore chain morphology of Rectus-Flexibilis (RF), spores in straight or flexuous chains, and Spira (S) (Tadei, Rodriguez, Márquez-Vilchez & Castelli 2006, p. 222).

Streptomyces Coelicolor: Characteristics

Belonging to the genus of Streptomyces, the phylum and class of Actinobacteria, the subclass of Actinobacteridae, the order of Actinomycelates, the suborder of Streptomycineae and the family of Streptomycetaceae (Celler et al. 2012), Streptomyces Coelicolor is Gram-positive (Thompson et al. 2010). It can also be described as filamentous (Speike 2015). The bacteria can be found in the soil, which predetermines outstandingly high rates of adaptability for the aforementioned type of bacteria (Moody, Jones & Eliot 2014). Indeed, Streptomyces Coelicolor may survive on a range of carbon sources, including D-ribose, L-xylitol, D-gluconate, etc. (Chen et al. 2009). The specified characteristics define the earthy smell of the bacteria colonies. On a range of levels, Streptomyces Coelicolor colonies share similarities with fungi (Joshi & Deshmunkh 2011).

Apart from the above-mentioned characteristics, the Streptomyces Coelicolor is easily detected due to its unique color scheme; the colony is usually of a grayish-yellow color (Clark et al. 2013), especially the element of the bacteria known as aerial mycelium (Clark et al. 2013). The melanoid pigment, in its turn, is purely absent in Streptomyces Coelicolor (Clark et al. 2013); more to the point, the aforementioned aerial mycelium does not have spirals in the specified strains of Streptomyces. A Streptomyces Coelicolor colony can also be characterized by its ability to self-assemble into two functional amyloids (Bokhove et al. 2012).

Natural Products

Though Streptomyces Coelicolor genome mining has only been given a major boost comparatively recently, the facts discovered over the past few years are sufficient for considering Streptomyces Coelicolor to be among the most promising research fields to explore. In the light of the fact that novel natural products have been discovered with the help of the genome-based approach, the need to explore the potential of the former and push the envelope by incorporating the newly discovered items into the healthcare realm emerges. The bioactive natural products mentioned by Laureti et al. (2011) are a major foot forward in addressing some of the most topical healthcare issues of the 21^st century. The discovery of the natural product-based drugs has obviously reinvented the realm of healthcare as people know it, and the use of cryptic gene encoding as the tool for the application of macrolides, polyenes, aromatics, and polyethers, which have found therapeutic applications as antibiotics, antitumor agents, immunosuppressants, and cholesterol-lowering drugs (Laureti et al. 2012, p. 6258) will clearly make a difference in healthcare.

Genome Mining over the Last 10 Years

In the course of the past decade, new tools for genome mining have been discovered, which can be noticed quite easily once the process of the Streptomyces Coelicolor genome mining is taken into account. Indeed, a closer look at the process in question will reveal that the element known as orphan gene has factored in the genome mining procedure, therefore, facilitating a far more expeditious method and creating the premises for retrieving far more fruitful results (Corre & Challis 2007, p. 7). The process of genome mining has clearly been geared towards the natural products retrieval process mentioned above, which the genome analysis of the Streptomyces Coelicolor mentioned above is a graphic example of. To be more specific, the discovery of the so-called orphan (Corre & Challis 2007, p. 8) genome clusters has predetermined the creation of the genomisotropic approach as the key strategy in the genome mining process (Corre & Challis 2007).

More to the point, the discovery of new products may ensue the use of genome mining as the basic approach in addressing healthcare and medicine-related issues from the perspective of genetics. As recent data shows, Many new natural products with potential clinical utility could therefore be discovered (Aigle & Corre, 2012, p. 362 Aigle & Corre, 2012, p. 362) with the adoption of the genome-based approach in general and the genome clusters strategy in particular due to the exploitation of the large number of untapped biosynthetic gene clusters (Aigle & Corre, 2012, p. 362).

Methods of New Antibiotics Discovery

As it has been stressed above, the use of the aforementioned bacteria allows for the discovery of new types of antibiotics and, therefore, a more efficient treatment of a range of disease, such as the carbapenem-resistant Klebsiella pneumonia (Procopio et al. 2912, p. 469), etc. As a rule, two key types of retrieving antibiotics from Streptomyces Coelicolor are distinguished as the most efficient ones. Though the overexpression of transcriptional activators has its problems as a method for antibiotics production, it is still generally preferred to the inactivation of repressor, as the latter allows for suppressing the natural product-based feedback inhibition (Navone et al. 2014).

Therefore, when it comes to defining the basic methods of antibiotic discovery, the methods such as the activation of the silent polyketide synthase (Laureti et al. 2011) deserves to be mentioned. Favored largely because of the simplicity of the process, it is often compared to fatty acid in terms of the ease and speed of antibiotics retrieval (Masschelein et al. 2015)

Overexpression of Transcriptional Activators

Traditionally preferred over the inactivation of repressor, the specified approach can be deemed as rather efficient in terms of antibiotics retrieval. According to the existing evidence, the method involving overexpression of transcriptional activators is more efficient due to the opportunity to inhibit the negative effect of the repressor, which it allows for (Pillai et al. 2001). Another obvious reason that makes the specified approach superior to that one of inactivating the repressor, the MM2 and MM5 production property must be brought up. Indeed, according to the results of the research concerning the subject matter, the pET151 plasmid was used to transform E. coli BL21star. LC-MS analyses of culture supernatant organic extracts showed that induction of mmfL overexpression in this strain resulted in the production of MMF2 and MMF5 (Corre et al. 2008, p. 17512).

Inactivation of Repressor

It would be wrong to claim that the inactivation of repressor is not legitimate as a tool for retrieving antibiotics with the help of Streptomyces Coelicolor. The transcriptional repressor GbnR in S. venezuelae (Sidda et al. 2013) allows for suppressing the effects of the gbn gene cluster (Sidda et al. 2013, p. 88). As a result, the production of antibiotic-like chemicals commences (Sidda et al. 2013). The given approach, however, needs to be fully tested yet, as the authors of the study admit it to be comparatively new and in desperate need for detecting the possible issues that may arise in the process (Sidda et al. 2013, p. 89).

Reference List

Aigle, B & Corre, C 2012, Waking up streptomyces secondary metabolism by constitutive expression of activators or genetic disruption of repressors, Methods in Enzymology, vol. 517, pp. 343366.

Bhave, S V, Shanbhag, P V, Sonawane, S K, Parab, R R & Mahajan, G B 2013, Isolation and characterization of halotolerant Streptomyces radiopugnans from Antarctica soil, Letters in Applied Microbiology, vol. 56, no. 5, pp. 348355.

Bokhove, M, Claessen, D, Jong, W d, Dijkhuizen, L, Boekema, E J & Oostergetel, G T 2012, Chaplins of Streptomyces coelicolor self-assemble into two distinct functional amyloids, Journal of Structural Biology, vol. 184, no. 2, pp. 301309.

Celler, K, Picioreanu, C, Loosdrecht, M C M v & Wezel, G P v 2012, Structured morphological modeling as a framework for rational strain design of Streptomyces species, Antonie van Leeuwenhoek, vol. 102, no. 3, 409423.

Chen, H-H, Qin, S, Lee, J-C, Kim, C-J, Xu, L-H & Li, W-J 2009, Streptomyces mayteni sp. nov., a novel actinomycete isolated from a Chinese medicinal plant, Antonie van Leeuwenhoek, vol. 95, no. 1, pp. 4753.

Clark, L C, Seipke, R F, Prieto, P, Willemse, J, Wezel, G P v, Hutchings, M I & Hoskisson, P A 2013, Mammalian cell entry genes in Streptomyces may provide clues to the evolution of bacterial virulence, Scientific Reports, vol. 3, no. 1109, pp. 18.

Corre, C & Challis, G L 2007, Heavy tools for genome mining, Chemistry & Biology, vol. 14, no. 1, pp. 79.

Corre, C, Songa, L, ORourke, S, Chater, K F & Challis, G L 2008, 2-Alkyl-4-hydroxymethylfuran-3-carboxylic acids, antibiotic production inducers discovered by Streptomyces coelicolor genome mining, PNAS, vol. 105, no. 45, pp. 1751017515.

Duong, A, Capstick, D S, Di Berardo, C, Findlay, K C, Hesketh, A, Hong, HJ & Elliot, M A 2012, Aerial development in Streptomyces coelicolor requires sortase activity, Molecular Microbiology, vol. 83, no. 5, pp. 9921005.

Flärdh, K & Buttner, M J 2009, Streptomyces morphogenetics: dissecting differentiation in a filamentous bacterium, Nature Reviews: Microbiology, vol. 7, no. 1, pp. 3649.

Jani, C, Tocheva, E I, McAuley, S, Craney, A, Jensen, G J & Nodwell, J 2015, Streptomyces: a screening tool for bacterial cell division inhibitors, Journal of Biomolecular Screening, vol. 20, no. 2, pp. 275284.

Joshi, A P & Deshmunkh, S S 2011, Streptomyces nucleases, Critical Reviews in Microbiology, vol. 37, no. 3, pp. 227236.

Laureti, L, Songc, L, Huanga, S, Correc, C, Leblonda, P, Challisc, G L & Aiglea. B 2011, Identification of a bioactive 51-membered macrolide complex by activation of a silent polyketide synthase in Streptomyces ambofaciens, PNAS, vol. 108, no. 15, pp. 62586263.

Lv, X-A, J, Y-Y, Li, Y-D, Zhang, H & Liang, X-L 2013, Genome shuffling of Streptomyces viridochromogenes for improved production of avilamycin, Applied Microbiology and Biotechnology, vol. 97, no. 2, pp. 641648.

Masschelein, J, Clauwers, C, Awodi, U R, Stalmans, K, Vermaelen, W, Lescrinier, E, Aertsen, A, Michiels, C, Challis, G L & Lavigne, R 2015, A combination of polyunsaturated fatty acid, nonribosomal peptide and polyketide biosynthetic machinery is used to assemble the zeamine antibiotics, Chemical Science, vol. 6, no. 1, pp. 923929.

Moody, M J, Jones, S E & Eliot, M A 2014, Complex Intra-Operonic Dynamics Mediated by a Small RNA in Streptomyces coelicolor, PlosOne, vol. 10, no. 1, p. e85856.

Navone, L, Casati, P, Licona-Cassani, C, Esteban, C-M & Lars , N 2014, Allantoin catabolism influences the production of antibiotics in Streptomyces coelicolor, Applied Microbiology and Biotechnology, vol. 98, no. 1, pp. 351360.

Pillai, B, Sampath, V, Sharma, N & Sadhale, P 2001, Rpb4, a non-essential subunit of core rna polymerase ii of Saccharomyces Cerevisiae is important for activated transcription of a subset of genes, The Journal of Biological Chemistry, vol. 276, no. 33, pp. 3064130647.

Procopio, R E d L, Silva, I R d, Martins, M K, Azevedo, J L d & Araujo, J M d 2012, Antibiotics produced by Streptomyces, The Brazilian Journal of Infectious Diseases, vol. 16, no. 5, pp. 466471.

Sidda, J D, Song, L, Poon, V, Al-Bassam, M, Lazos, O, Buttner, N J, Challisa, G L & Corre, C 2013, Discovery of a family of g-aminobutyrate ureas via rational derepression of a silent bacterial gene cluster, Chemical Science, vol. 5, no. 1, pp. 8689.

Slama, N, Mankai , H, Ayed, A, Mezhoud , K, Rauch, C, lazim, H, & & Limam, F 2015, Streptomyces tunisiensis sp. nov., a novel Streptomyces species with antibacterial activity, Journal of Biomolecular Screening, vol. 20, no. 2, pp. 275284.

Speike, R F 2015, Streptomyces albus, PlosOne, vol. 1, no. 1, p. e0116457.

Tadei, A, Rodriguez, M J, Márquez-Vilchez, E & Castelli, C 2006, Isolation and identification of Streptomyces spp. from Venezuelan soils: Morphological and biochemical studies. I., Microbiological Research, vol. 161, no. 3, pp. 222231.

Taichi, E T, Book, A J, Lewin, G R, Currie, C R & Fox, B G 2012, Aerobic deconstruction of cellulosic biomass by an insect-associated Streptomyces, Scientific Reports, vol. 3, no. 1030, pp. 110.

Thompson, B J, Widdick, D A, Hicks, M G, Chandra, G, Sutcliffe, I C & Palmer, T 2010, Investigating lipoprotein biogenesis and function in the model Gram-positive bacterium Streptomyces coelicolor, Molecular Microbiology, vol. 77, no. 4, pp. 943957.

Qi, H, Zhao, S, Fu, H, Wen, J & Jia, X 2014, Coupled cell morphology investigation and metabolomics analysis improves rapamycin production in Streptomyces hygroscopicus, Biochemical Engineering Journal, vol. 91, 186195.

Summary

This article was posted by Sue White in 2013 to the ABC Environment (Australia) Website (White, 2013). The main topic of the article is the need for chemists across the world to enhance the adoption of green chemistry as a viable countermeasure toward eliminating chemical disasters in the world. White (2013) started by highlighting the Bhopal disaster in India, which was a result of toxic gases being released from a pesticide plant. The Bhopal disaster led to the death of thousands of people in the area before it could be contained. Green chemistry aims at reducing air pollution in chemical processes and limiting the toxicity of the by-products of various indispensable processes. For instance, green chemistry is geared toward eliminating cases of products derived from chemical processes causing illnesses. Many products have been associated with the development of cancer in human beings because of the toxicity of the molecules used to develop them; hence, green science compels chemists to design safer approaches in the production of commodities for human consumption. One of the examples of green chemistry provided in the article includes the production of paint from vegetable oil. This approach promises to reduce the toxic byproducts from the process of making paint through petrochemicals. Green chemistry promises a safer future for the global society, but it calls for chemists across the world to be highly innovative.

Thoughts

The traditional approach to the production of consumption products through chemistry has led to an increase in pollutants in the air, especially as the demand for the associated products is concerned. The adverse effects of the increase in toxic emissions to the atmosphere include faster rates of global warming, an increase in cases of cancer and respiratory diseases, and toxic chemicals in rainfall (White, 2013). Green chemistry promises to eliminate the high rates of air and water pollution, and it will promote better health for people. It is a plausible concept because it will also eliminate the hazards associated with the mass manufacturing of various products. Chemists in the future will enjoy conducting safer experiments in the laboratories if there will be more discoveries toward the same. It is essential for governments to fund studies that aim at enhancing knowledge in green science.

Tying the Article with Class Concepts

There are many warnings and hazards pinned in chemistry laboratories to caution chemists against toxic molecules and other risks in the lab. Lab safety in chemistry is one of the topics that were covered in this course, and it is apparent that most of the hazards are tied to the chemical substances used in the contemporary science world (White, 2013). Most of the experiments in the lab were associated with the emission of toxic pollutants, and some lab experiments had to be conducted in extremely controlled environments. Following this observation, it is apparent that chemists need to start developing safer ways to produce commodities. Not only is a greener approach going to lower the hazards associated with chemical processes in the laboratory, but it will also make the mass production of commodities safer for the society. Chemists should develop mechanisms to produce the same products with a minimal number of toxic byproducts. When looking at the idea of producing paint and the related products from vegetable oil, it is apparent that thinking beyond the obvious parameters of chemistry will help chemists to come up with greener methods of manufacturing different products.

Reference

White, S. (2013). Saving The World Through Chemistry. Web.

Halophiles usually thrive in salty environments and they are categorized according to the extent of their tolerance for highly saline environments, ranging from slight, moderate and extreme. Their adaptability to these highly saline environments, which have limited habitation by life forms, has drawn the interest of scientists who seek to understand the biochemical mechanisms involved under such conditions for possible usage of their enzymes (Ollivier, Hatchikiern, Precier, Guezennec, and Garcia 50). The organism H. Halobium has a membrane structure design that makes the optimal habitat for it a hyper saline environment. The salinity of the water bodies can be attributed to the high rates of evaporation due to high temperatures

The habitats for halophiles as already indicated, are characterized by variability in composition ranging from high salt content of up to 8.9 to 10% (wt/vol) together with high pH levels of 9 to 10 (Oremland and King 181), while others exhibit salt concentration of up to 20 % (wt/vol) with pH levels of 7. The halophile H. Halobium is found in the Great Salt Lake, which is a hyper-saline eco system. The conditions for this environment will encompass up to the 20 % salt concentration with the pH of 7.

The predominant ions in the Great Salt lakes and similar habitats are Na⁺ and Cl^, with Na⁺ having a concentration of 105.4 whilst Cl^ is 181g/liter. This high concentration of NaCl makes oxidation of organic substances incomplete compared with other ecosystems. Besides these two ions, however, there are other ions like the sulphate ion, though at low levels due to precipitation in this lakes, which acts as an important electron acceptor and aids in the mineralization of organic matter in the ecosystems. It also has Ca⁺ at a concentration of 17.2g/liter which is an important divalent cation similar to Na⁺.

The habitat envisaged for H. Halobium also has a concentration of organic matter which is a result of the dead cells of the metabolites of the Halophiles growing in the water, and which raises the concentration of salt in the habitat to an extent that the vegetation growing nearby would die if the water levels were raised by an occurrence like rainfall to reach their growth and consequently submerge them like the case reported once in a hyper saline African lake ( Ollivier, Caumette, Jean-louis mah 28). The organic matter also originates from the algae and vegetation growing on the banks of the lakes. Therefore, the limited biodiversity of this environment would only allow methanogenic species of the archaea, like the halobacteria, to survive at the NaCl concentration of 20% exhibited in these hyper saline lakes. The key to survival in this otherwise hostile environment is the ability to adapt to various conditions presented to the H. halobium cells.

A crucial composition of the plasma membrane surrounding the organism is the ether lipids which are unique for purposes of maintaining homeostasis in the organism. The lipids have branched and saturated fatty acids which are different than other organisms. They are characterized by ether bonds and branched by isoprenoid chains rather than ester bonds and fatty acyl chains as found in other organisms. These lipids are much more stable than other organisms making them able to survive in extreme conditions. Phospholipid Archaetidyglycerol methylphosphate (PGP-Me) is another key composition of the membrane that makes the cell membrane more stable in the prevailing saline conditions. Large unilamellar vesicles (LUV), produced by the polar lipids retain carboxyfluorescein, this further counteracts the effects of the saline environment within the range of 0-5 m NaCl; giving the cell its rod-like shape. H. halobium maintains a large surface of lamellar within the lipid that displays stability, when exposed to high temperatures of up to 100 degrees Celsius. PGP-Me in the lipid layers has a dual charge that gives the cell stability via its electrostatic repulsion forces.

The S-layer of H. halobium is a two dimensional crystal structure, formed from S-layer glycoproteins. The two dimensional structure produces a matrix of glycans structures. The cell layer has to protect the membrane against extreme osmotic conditions. The S-layer contains two proteins namely: SlaA and SlaB. These proteins interact with each other in a process called glycosylation, to remain anchored to the main cell membrane. The S-layer also, helps in the glycosynthesis process of the cell; enabling a bacterial generation time of 20 seconds. The S-layered glycans are also important for typing strains of the H. Halobium. This layer also has the ability to adapt to various environmental changes.

H. Halobium has adapted to its hyper saline habitat in such a way that allows it to overcome problems caused by osmotic pressure. The organism defeats osmotic pressure by producing a solute that is positively charged. The cell produces positively charged K⁺ ions that counteract the effects of the saline environment. The ions make the cell isotonic to the saline habitat around it (Mescher, Strominger 2009). Water usually diffuses out of their bodies to the environment due to the hyper saline condition. Other organisms would die if subjected to such environments but H. Halobium is able to prevail.

The surface proteins of H. Halobium are negatively charged as a result of a high ration of basic to acidic amino acids allowing the proteins to be solvated in its hyper saline habitat and to further prevent denaturation, aggregation and denaturation. Another important protein that H. Halobium contains is the bacteriordhodopsin, which is found in arrays within the cell membrane. This protein is a pigment that functions as chlorophyll in green plants. It uses light from the sun as energy to pump protons across the cell membrane. This has an effect of causing the internal environment to be more alkaline than the surrounding environment. To add on this, H. Halobium also has a unique feature in its membrane to help in locating areas in the water with high concentration of oxygen. This feature includes novel gas vesicles which enable the organism to float in the water to tap oxygen from the environment, or if there is a need for more stable salt concentrations, it allows H. Halobium to sink deep into the water in areas where the salinity is optimum (Studier 240).

From the examination of existent habitat and membrane design of the H. halobium explored in this paper, it can be seen that the organism is very unique in composition, different from many other organisms because the saline habitat presents very severe living conditions and therefore leaving it with option adaptation. From the ionic composition, salinity and pH, to the unique features of the membrane and other adaptive features, a clear picture is shown on how to design the membrane and habitat of the organism.

Works cited

Mescher ,Strominger. Purification and characterization of a prokaryotic glycoprotein from the cell envelope of Halobacterium salinarium. J Biol Chem 10. 251 (7), (2000): 251-256. Web.

Ollivier, E., Garcia J. L., Guezennec J., Hatchikiern C. E., and Prensier G. A halophilic sulfate-reducing bacterium from sediments of a hyper saline lake in Senegal. Int. J. Syst. Bacterial 41:7481 (1991). Web.

Oremland, R. S., and King, G. M.. Methanogenesis in hyper saline environments. In Y. Cohen and E. Rosenberg (ed.), Microbial mats: physiological ecology of benthic microbial communities. American Society for Microbiology, Washington (1989): 180-190. Web.

Studier, J. Analysis of bacteriophage T7 early RNAs and proteins on slab gels. J Mol Bio 79 (1973). 237248. Web.

Most Surprising Historical Account on Birth Practice

The author of this book has presented the historical accounts of birth in such a way that it is not easy to single out the most surprising practice. Almost all the practices are surprising for the reader, as it is hard to believe that these types of childbirth used to occur in the past. However, after a thorough reading of the book, I came to recognize that women who underwent the caesarean method of child delivery found it difficult to bear. There was no anesthesia to reduce the pain, yet the society expected the women to be strong and give birth to healthy children. Most midwives were said to be inexperienced at the time, yet they were the most reliable people in assisting pregnant women deliver.

Choice of Midwife

I would have gone to a midwife if I had found myself pregnant before reading this book. The agony of giving birth while alone is risky, as the pain could rise to levels that are unbearable. Sometimes, there are reports that the unborn child is in such a dangerous position that the mother may have a stillbirth if no prompt action is taken before delivery. In such a case, the midwife would come in handy in trying to palpate the womans womb in order to bring the child to the correct position before delivery. Midwives have been reported to be very supportive in child delivery. They give encouragement to the pregnant woman by assuring them that the process of childbirth will be over successfully if the woman holds on. Therefore, I would not hesitate to visit a midwife for assistance in child delivery.

On the other hand, if I got pregnant after reading this book, then I would hesitate to visit a midwife. This book has discouraged the use of midwives in child delivery, as they are normally inexperienced. Midwives do not administer any anesthesia; thus, there are high chances that the mother could succumb to the pain that is experienced during caesarean delivery and lose the baby in the process too. Some midwives are also reported to be arrogant to the mother to a point that the mother can be discouraged from ever giving birth in the care of midwives in the future. In addition, midwives are said to have little medical knowledge; therefore, they would offer little or no medical help in case there is a complication during child delivery. The effect of the inexperience is that many women, as well as their children, have died in the hands of midwives. However, one question that I would ask myself is: Where else can I get help during childbirth? The answer to this question would determine whether I would go to the midwife or not. In case the only available assistance is the midwife, then I would reasonably seek her intervention than growl in pain all by myself. However, if there would be a medical facility nearby, I would prefer the medical center that has qualified medical personnel to a midwife who has little or no medical education.

Book Review

The book is organized into events that follow each other in a smooth succession. The writer has put considerable effort to explain how different generations choose different methods of childbirth. These methods are said to have been influenced by different circumstances, such as cultural, political, and religious orientations. The history of childbirth has been explained in such a way that it is obvious that the reader will appreciate the current advances that have been made in the delivery of children. The writer has given the role of midwives, family set up, and the community in the delivery of a child. The author of this book has used a unique way of delivering her message; she has infused history with medical science. In other words, the author uses her experiences, as well as the experience of her other mothers in child delivery to give a history of what used to happen during childbirth in the past. One could mistake the book for a novel or a mere historical book.

I would recommend this book for nursing students, as they would be able to understand and appreciate the various advances that have been made in the delivery of children. The language used in this book makes it clear to nursing students that child delivery is not just a walk in the park. Therefore, nursing students are expected to handle pregnant women in a way that shows empathy and support for these women. On the other hand, I would not recommend this book for expectant women. The kind of ruthless experiences that women who are mentioned in this book went through would scare pregnant women from giving birth. Indeed, the pregnant women would become stressed because of the fear that they may also go through the same trauma.

What I have learned from the Book

This book has many learning experiences. One can appreciate the role of different sociological groups in past child delivery. However, the most important piece of information that I have learned from this book is the appreciation of how far the medical field has gone to make advances that are useful in child delivery. One cannot help but be amazed at the current equipment and services that are available in medical facilities for use in child delivery today. The effectiveness of the modern support in child delivery cannot be compared to what used to happen in the past.

In the current world, significant theoretical shift in the link between scientific exploration and ethics has taken place. The time difference between ethical consideration and parallel scientific inventions is slowly vanishing. This simply means that ethics has set up its own cadence. This change has been unfalteringly led to the current bioethics of developing sciences. Currently, as science has continued to pursue its endeavours, bioethics has on the other hand continued with its contemplations.

In the video by Craig Venter, scientists have gone a step ahead to create an artificial life. Genetic components designed by computers are transplanted into a bacterial cell to form an artificial life. Though this has been one of the worlds greatest scientific discoveries, ethicists have raised issues regarding the nature and the inception of life. Proponents of science oppose ethics on the grounds they only speculate and never come up with concrete answers. Hence, ethicists believe that creation of artificial life plays God, while scientists think that this is a breakthrough.

The video was so perfect in the changing the attitude held towards life. Questions of life are prevalent in peoples minds and a definite answer has not been reached. Since the time of Aristotle, philosophers, theologians and scientists have made numerous attempts to explain the nature and the inception of life. Some have argued that life emanates from the soul, while others think that life involves a nontrivial force that differentiates life from lifeless. The video by Craig has come with a new dimension towards the nature and the inception of life. It is now apparent that with the correct composition of inorganic chemicals to create DNA series, and the correct broth within the cell that accepts the DNA, living organism comes out as a result (Synthetic Life Video Presentation).

The most persuasive information given by Craigs video concerns the question of life. For long scientists, theologians and philosophers have unsuccessfully made attempts to come up with a clear explanation of the nature and the inception of life. This video gives an overt signal that the concept is not alien. Man can now use biology to explain the nature and the inception of life. The video gives a tick to proponents of mechanistic reductionists of inanimate life.

The video manifests the existence of a wide trend in biological and physical sciences. This is the trend that has over the last few decades mutated to empower humanity to manipulate the inorganic and the organic component at its most fundamental levels (Synthetic Life Video Presentation).

Craig never created an actual life, but a form of life. His experiment only works in bacteria and not in humans. In his experiment, a living bacterium is integrated from synthetic materials. Critics have termed the experiment as unauthentic, tedious and maladroit. In the new form of life learned from this experience, required components are produced through the synthesizing and sequencing of DNA. Hence, Craigs discovery promises cheaper and quick improvement, simplification and synthesis of new creatures. Maybe in the future Craigs followers will discover real life by use of technology.

Through this discovery and its practice, scientists for sure are now crossing the boundaries. Though many people would see it as a big scientific step, it would also be viewed as an achievement that degrades an elementary belief about the inception and nature of life. The alteration of this belief would lead to further distortion of the view towards life and human role in the universe.

Therefore, though technology is important and has lessened human problem, helped discover the nature, scientists should limit their pursuit to a certain level. Some discoveries that may undermine the law of nature or work against God should be avoided. In as much as humans seek to understand the world, it should be realized that human knowledge is very limited and cannot surpass the supernatural.

Work cited

Synthetic Life Video Presentation. Ex. Prod. Craig Venter. YouTube, Vic.: Video Education U.K. 2008. DVD.

Introduction

The human chorionic gonadotrophin (hCG) is a member of the heterodimeric glycoproteins hormones family which also includes the human follicle-stimulating hormone, the luteinizing hormone (LH), and the human thyroid-stimulating hormone (Dimiri and Kayisli 5). The subunit found in these hormones is identical but the b subunit varies from one hormone to another. HCG usually exists in three variants that are identified as regular HCG, the free b- subunit HCG, and the hyperglycosylated HCG (Gever 2). The three forms of HCG perform different biological functions. Apart from the three biological variants of HCG, other forms exist and include the secreted asubunit and eight other forms that are degraded following secretion. These degraded forms are found in urine or serum samples that are taken during pregnancy. These degraded forms are also found in patients suffering from a gestational trophoblastic disease (GTD) and nontrophoblastic malignancies (Honegger, Mann and Thleeruf 2). Several commercial tests have been developed to measure the levels of the different forms of HCG in the investigation of pregnancies and disease states in which they are elevated. This paper seeks to evaluate the different HCG tests with the aim of establishing the most selective and sensitive one. In order to correctly identify the best method, the paper will first address the various applications of HCG testing.

Applications HCG testing

Pregnancy testing

HCG is used to test for pregnancy as a medical examination for the use of certain steroids or following a request by a woman who wants to ascertain her pregnancy status. Hyperglycosylated HCG is predominant in early pregnancy but this often shifts to regular HCG as time progresses (Muller 8). A screening method should be able to detect the hypoglycosylated HCG, in addition to regular HCG if the pregnancy is to be detected early enough (Cole 2).

Gestational trophoblastic diseases (GTDs)

GTDs are disorders that are seen in pregnant women. Multiple forms of HCG are used to classify GTDS. Regular HCG is often used to identify partial and complete hydatidiform moles (Vareiro, Liu and Knoll 5). On the other hand, choriocarcinoma is identified using hyperglycosylated HCG. The enzymes produced by macrophages in these disease states initiate the degradation of regular and hypergycosylated HCG molecules (Willet 6). Its therefore important to detect the different variants of HCG in GTDs.

Nontrophoblastic neoplasms

HCG variants form important markers for germ cell and other nontrophoblastic malignancies (Mehra, Huria and Gupta 7). Most germ cell tumors produce the free ²-subunit. Normally, the free ²-subunit and the ²-core fragment are used as common markers for neoplasms (Honegger, Mann and Thleeruf 6).

Quantitative serum HCG assays (Immunometric assays)

Quantitative assay methods are based on the principle that a capture antibody binds on a single HCG site, immobilizes it, then a second (tracer) radioactive iodine or enzyme-labeled antibody binds to a distant HCG site forming a complex that can be quantified. The amount of the tracer antibody is directly proportional to the HCG concentration (Cole 3). All the available commercial immunoassay hCG tests are immunometric assays. This can further be categorized into two clear HCG test groups. The intact HCG tests that only detect the HCG dimer and the total HCG (²-hCG) tests further detect that detect the ²- subunit, other variants and the degraded HCG, in addition to the intact HCG (Butler and Cole 2). The major limitation associated with the intact HCG test is the inability to evaluate dissociation in standards. Standards may dissociate as a result of transportation, storage and during usage in the automated platforms. The ²-hCG test is able to detect the dissociated standard (Honegger, Mann and Thleeruf). The ²-hCG or total assays are mostly utilized in the current commercial laboratory. The assays usually involve an antibody against the ²-subunit folded core 1 or 2 in combination with an antibody to the ²-subunit CTP natural (Breda 11). This eliminates the risk of a cross-reaction with LH, due to the fact that LH lacks the 30-amino acid CTP. The major limitation associated with the use of this combination of antibodies is their dependence on the O-linked oligosaccharide structure of the C- terminal segment (Kim, Josephson and Langer 17). The O-linked oligosaccharide accounts for most of the segments molecular weight. Thus most assays using this combination of antibodies will show a poor detection of the hyperglycosylated HCG and completely fail to detect HCG that lacks the C-terminal segment. The HCG produced in GTD and cancer usually lacks the C-terminal region. This limitation is overcome by using an alternative method that utilizes two to the HCG ²-subunit folded core 1 or 2, as used by the Siemens Immulite HCG test (Cole 6). This combination is able to detect all the HCG forms and the majority of the dissociated variants.

The figure above shows the HCG epitopes that are commonly used.

POC & OTC HCG assays

The POC and the OTC rapid pregnancy tests also rely on dual antibody immunometric technologies (Muller 13). The functioning of these tests is based on the immobilization of one antibody in a translucent line and the other one that might be labeled with a red or blue or gold matrix dye is allowed to mix with serum or urine. The HCG dye antibody complex moves along the strip until it reaches the result window where it is stopped by the immobilized antibody. Positive results are indicated by a visible line that is formed by the immobilized antibody- HCG-dye antibody complex (Williams 25). There are four different types of POC and OTC test devices for HCG testing. This includes the nitrocellulose plastic stick devices that are directly immersed in urine and positive results indicated by the formation of a line (Willet 7). The nitrocellulose plastic sick devices form the most common form of OTC HCG testing devices (Huang and Huang 23). The second type of devices only differs by being positioned on a flat surface whereby the urine sample is added by a pipette. Positive results are indicated by a line in a second window. These are the most commonly used POC devices. The third type is basically in the form of an open nitrocellulose dipstick. The forth type is composed of digital devices that digitally display the results using words such as yes or No, and Pregnant or Not pregnant (Vareiro, Liu and Knoll 12). The digital devices are available for use as both POC and OTC products.

The specificities, sensitivities and the ability of POC and OTC devices to detect pregnancies vary depending on the company that makes the specific device. A study carried out in the United States established that devices manufactured by Church & Dwight Inc. are highly sensitive as they are able to detect regular HCG, free ²-subunit and hyperglycosylated HCG on an equal basis (Mehra, Huria and Gupta 5). They however fail to detect the urine ²- core fragment. Devices manufactured by other companies either fail to detect or show poor detection of the three variants.

Analysis and Conclusion

The analysis above shows that most commercial HCG assays detect the regular HCG but vary in the detection of other variants. Its important to note that the detection of up to 11 HCG variants is crucial for the application of HCG in pregnancy testing, GTD and cancer tests.. In the US, the FDA has only approved the use of HCG tests in pregnancy testing. However, the specificity of the tests is highly required to distinguish between the different variants that manifest a given condition if HCG tests are to be used for other applications. For instance, only the hyperglycosylated HCG is the only HCG variant that is found in serum and urine samples during early pregnancy (Cole 13). Additionally, only the free ²-subunit is produced in cancerous states. The above analysis has established that quantitative assays that utilize HCG ²-subunit folded core 1 or 2, as used by the Siemens Immulite HCG test are able to detect all the HCG forms and the majority of the dissociated variants (Mehra, Huria and Gupta 9). Thus, in conclusion, the HCG ²-subunit folded core 1 or 2 quantitative assays will be regarded as the most sensitive and selective HCG test. Such a test should be recommended for the most reliable HCG testing.

Works Cited

Breda, Edward Van. ndrogenic anabolic steroid use and severe hypothalamic-pituitary dysfunction: a case study. nt J Sports Med (2003): 24 (3): 1956. Print.

Butler, Samson and Laurent Cole. Detection of early pregnancy forms of human chorionic gonadotropin by home pregnancy test devices. Clinical Chemistry (2001): 47 (12):213-2136. Print.

Cole, Laurence. Huma Chorionic gonadotropin tests. Expert Rev. Mol. Diagn. (2009): 9 (7): 721747. Print.

Dimiri, Arici and Guzeloglu Kayisli. Human chorionic gonadotropin contributes to maternal immunotolerance and endometrial apoptosis by regulating Fas-Fas ligand system. J. Immunol (2003): 171 (5): 2305-13. Print.

Gever, John. FDA Yanks HCG Weight Loss Agents from Market, New york: Medpage today, 2011. Print.

Honegger, Jurgen, et al. Human chorionic gonadotrophin immunoactivity in cystic intracranial tumours. Clinical Endocrinology (1995): 42: 235-241. Print.

Huang, Lee and Sun Huang. Lysozyme and Rnases as anti-HIV components in beta-core preparations of human chorionic gonadotropin. Proc. Natl. Acad U.S.A (1999): 96: 2678-2681. Print.

Kim, Grace, et al. Magnetic Relaxation Switch Detection of Human Chorionic Gonadotrophin. Bioconjugate Chem (2007): 18: 2024-2028. Print.

Mehra, Reeti, et al. Choriocarcinoma with negative urinary and serum B humaman chorionic gonadotropi- A Case Report. J Med Sci (2005): 59 (10): 538- 541. Print.

Muller, Collins. The quagmire of hCG and hCG testing in gynecologic oncology. Gynecol. Oncol (2008): 112(3), 663672. Print.

Smiz, Schiettecatte, Ver Elst and Mees Lecomte. Analytical and clinical evaluation of a human chorionic gonadotrophin plus b (hCG + bhCG) immunoassay in germ cell tumours and gestational trophoblastic disease. Immuno-analyse & Biologie (2005): 20:11-15. Print.

Vareiro, Margarida, et al. Surface Plasmon Fluorescence Measurements of Human Chorionic Gonadotrophin: Role of Antibody Orientation in Obtaining Enhanced Sensitivity and Limit of Detection. Anal. Chem (2005): 77: 2426-2431. Print.

Willet, Colditz. Induced and spontaneous abortion and incidence of breast cancer among young women: a prospective cohort study. Arch. Intern. Med (2007): 167 (8)814-20. Print.

Williams, Lance. Hormone-Free HCG drops quickly replacing homeopathic counterparts, San Fransisco : San Fransisco Chronicle , 2009. Print.

Introduction: Problem Statement

One of the deadliest diseases of the 21^st century, cancer not only increases death rates among people of all ages impressively (Mulder, 2014), but also triggers major health complexities even after a successful surgery (Mandelblatt, 2014). In their article Effects of cognitive status on life participation of cancer survivors, Baxter, Smith and Wahowski discuss the drops in the rates of cognitive status among cancer survivors, making it clear that a post surgery therapy is crucial for every cancer patient; otherwise, a rapid and significant change in the cognitive processes of the patient is expected and can hardly be prevented.

The study is quite coherent and well organized. It provides a detailed list of the key observations made by the researchers and focuses on both the methodology and the theoretical background of the study greatly. Despite minor issues with the literature review, the study represents a very peculiar and interesting specimen of a qualitative research.

Purpose and Research Questions

The purpose of the study is quite obvious  the authors state from the very beginning that, over the past few decades, a major concern regarding the changes in the cognition processes of cancer survivors has arisen. Several studies have shown that people, who have undergone cancer surgeries, experience considerable problems with cognition and memorizing. Baxter, Smith and Wahowski, therefore, state the purpose of the study in a very explicit and clear manner; according to the researchers, the results are bound to show if the connection between drops in cognitive abilities has anything to do with the surgery and the cancer treatment, or whether the aforementioned observations are merely a train of coincidences.

The research question is stated rather clearly; Baxter, Smith and Wahowski put it in the following way: the goal of the research, as the authors explain, is to identify the cognitive status of cancer survivors (Baxter, Smith & Wahowski, 2014, p. 2). Herein the purpose of the study lies; the authors of the article are obviously aiming at measuring the effects that cancer treatment, as well as the disease itself, has in patients and their ability to handle new information, including the process of data acquisition, processing, and usage. It should be mentioned. Though, that the research question is never mentioned, but only implied. Instead, the study authors make a major emphasis on the methodology of the research, particularly, the tools that they use in order to collect the data. Indeed, the questionnaires, with the help of which the information is gathered, is mentioned quite a few times in the article.

Literature Review and Its Quality

As Baxter, Smith and Wahowski explain, the key problem with the study that has been conducted concerns the lack of evidence on the issue. Despite the fact that cancer is, unfortunately, a very common disease, the information concerning the link between cancer and mental disorders, especially such specific ones as the loss of memory or concentration, is very scanty, which does not allow for a full-fledged research. Consequently, the literature review is the weakest aspect of the study. Indeed, the study features no review; instead, the authors mention scraps of uncoordinated pieces of information, which support the study at least to some extent: Much of the literature indicates that changes in daily tasks are frequent side effects of cancer and cancer treatments (Baxter, Smith & Wahowski, 2014, p. 11). One might argue that the few sources, which the authors of the study use to support their hypothesis, are current; however, these sources have not been organized into a solid review of the available sources. True, the sources provided as references in the article make sense and support the authors vision quite well. Nevertheless, the methodology of the study compensates the lack of literature analysis. Indeed, a closer look at the study will show that Baxter, Smith and Wahowski decided to choose questionnaires as their basic tool for information retrieval. While questionnaires do have a tint of subjectivity around them, with the results restricted to the opinions of a relatively small group of people, such a tool, nevertheless, creates the opportunity for considering real life situations and collecting data directly from patients. Thus, the dubious quality of the literature review can be leveled with an outstanding choice of the research tool.

Conceptual and Theoretical Framework

Even though the research lacks a literature review, it still has a decent theoretical foil to back its analysis on. Baxter, Smith and Wahowski use the Occupational Therapy Practice Framework (OTPF) as the basis to build their argument on, and they do so in a very successful way. With the help of the aforementioned theory, such functions of the brain as attention, memory, perception, and thought (Baxter, Smith & Wahowski, 2014, p. 10) are analyzed, the pre-surgery data compared to the information retrieved after the surgery took place. Since some of the framework, including the possibility of cognitive function deterioration, have been developed from the study results, it can be assumed that the researchers have used the grounded theory method.

Reference List

Baxter, M. F., Smith, T. & Wahowski, J. (2014). Effects of cognitive status on life participation of cancer survivors. The Open Journal of Occupational Therapy, 2(2), 117.

Mandelblatt, J. S. (2014). Cognitive impairment in older patients with breast cancer before systemic therapy: Is there an interaction between cancer and comorbidity? Journal of Clinical Oncology, 32(18), 19081920.

Mulder, S. F. (2014). Impairment of cognitive functioning during Sunitinib or Sorafenib treatment in cancer patients: a cross sectional study. BMC Cancer, 14(219), n. p. Web.

Testing for statistical significance depends on the chosen p-value. Selection of the p-value depends on the sample size (Banerjee, Chitnis, Jadhav, Bhawalkar, & Chaudhury, 2009; Ioannidis, 2005). This determines the location of desired significance on a normal distribution graph. Definition of the alternative hypothesis guides the selection of the left hand-tail, right-hand tail, or both tails. Selection of a large positive p-value is more plausible when considering alternative hypothesis. However, when a null hypothesis is the main concern for the test statistic, a small positive p-value is the most appropriate. The p-value provides the measure of distance for the test statistic of a null distribution within the right-hand tail. Therefore, lowering the p-value tests how far the test statistic is in that tail. Small p-values signify strong evidence against null hypothesis. Therefore, one would lower a p-value when interested with null hypothesis. This will give stronger evidence against the null hypothesis as opposed to alternative hypothesis, hence justifying the rejection of null hypothesis.

Explain how p-values that are 0.050, 0.049, and 0.051, might be different when interpreting statistical results.

P-value tests two assumptions. These are no effects on the interventions, and no difference in the effects of interventions between herogenous studies. Appropriate interpretation of statistical results based on p-values should be guided by a sample size and the 95% confidence interval (Banerjee et al., 2009; Ioannidis, 2005). When a p-value of 0.051 is obtained, it may be misinterpreted as evidence of no effect. However, the best interpretation of no stronger evidence on the effect is different from that outlook. P-values of 0.050 and 0.051 are equal and greater than the set limit hence signifying no stronger evidence that the interventions have effects. However, in small meta-analysis or small studies these p-values are common, which may signify a range of effects hence the need to include substantial effect and no intervention effect. In such cases results should not be described as non-significance or not statistically significant but as no stronger evidence that interventions have effects (Banerjee et al., 2009; Ioannidis, 2005). P-values less than set limit like 0.049 signifies detection of trivial effects. This should not be interpreted as implying that interventions have important effects without considering confidence interval and point estimation.

Explain why p-values are significant in contributing to public health practice. Be specific and provide examples.

P-values are the basis for accepting or rejecting the research hypothesis that guides public health practice. This has a significant contribution to this sector because the current trend in medical fraternity is evidence based approach. Clinicians design certain treatment practices or diagnosis regimes based on available studies (Banerjee et al., 2009). The p-value used in any important study must therefore reflect the outcome of the research. Selection of a p-value based on the sample size and its interpretation guides good practices in medical profession. This has a significant impact in making policies and other decisions that guides provision of such services (Browner, & Newman, 1987); Ioannidis, 2005). Scientist carrying out research needs to select appropriate p-value for their study based on a sample size and give appropriate interpretation that can help formulate policies for a public health practices.

Suggest how p-values may compromise the reliability of statistical results in public health practice.

Selection of p-values for a particular study reflects the outcome from that study. This depends on sample size of the population under the study. If the population is small a larger p-value should be selected when testing alternative hypothesis. However, when studying a larger population a smaller p-value should be selected to increase reliability of the output. When designing a diagnostic test, appropriate sample size needs to be selected for a representative outlook on the outcome of the study. Selection of p-value in such a case guides the possibility of obtaining error type I and error type II which may compromise utilization of research (Banerjee et al., 2009).

References

Banerjee, A., Chitnis, U. B., Jadhav, S. L., Bhawalkar, J. S., & Chaudhury, S. (2009). Hypothesis testing type I and type II errors. Industrial Psychiatry Journal, 18(2), 127-131.

Browner, W.S., & Newman, T. B. (1987). Are all significant p values created equal? The analogy between diagnostic tests and clinical research. Journal of the American Medical Association, 257(18), 2459-2463. Web.

Ioannidis, J. P. A. (2005). Why most published research findings are false. PLOS Medicine, 2(8), 124.

Overview of thermal-chemical disinfection process

Disinfection is a process of reducing microorganisms to a level that is not harmful to health (Fraise, Lambert, & Maillard, 2003). The disinfection process can be a single step where the disinfectant is the sole means of controlling microbial growth such as contact lens solution and disinfection of household surfaces (Knight & Cooke, 2002). Also, it can be a multi-step process where chemical disinfection can be used along with mechanical or thermal disinfection such as in industry where disinfection usually follows a cleaning and rinsing step (Knight & Cooke, 2002). Thermal disinfection uses high temperatures to achieve disinfection, while chemical disinfection uses chemicals (Fraise A & Ayliffe, 2000). These two processes can be used together to achieve disinfection in a process termed as thermal-chemical disinfection (Gardner & Peel, 1998; Fraise, Lambert, & Maillard, 2003).

Plots of Inactivation curves of each vegetative bacteria

Staphylococcus aureus colony forming units decreased significantly within 1 minute at 20^o C due to thermal chemical disinfection, and by firth minute, there were 150cfu/ml. At 35^oC, a significant number of cfu/ml was still present, but at 20^oC, the levels had declined sharply as shown in the plot for Staphylococcus aureus.

Streptococcus feacalis cfu/ml declined sharply within the first minute at 35⁰C. However, there was growth and some multiplication within the next minute followed by inactivation in third to the fifth minute. For both 5⁰C and 20⁰C, the cfu/ml declines gradually to a low level from time zero to the third minute as shown in the plot.

E. coli, a common inactivation trend is observed. Although, the greatest inactivation rate was observed at 35^oC.

Determination of D values* for each organism and comments

The data selected for the three vegetative bacteria is from time 0 to time 5 minutes because using logarithm to base 10, the data becomes linear, and would be more representative of the inactivation process. The units for the inactivation rate are colony forming units per ml per minute.

For Staphylococcus aureus the D values* are:

It can be concluded that for Staphylococcus aureus, the highest inactivation rate was 1.1677cfu/ml/minute at 35^oC, whereas the lowest was at 5^oC. The highest inactivation rate for Streptococcus feacalis was 1.2056cfu/ml/minute at 20^oC and the lowest was at 5^oC. The highest inactivation rate for E.coli was 1.1361cfu/ml/minute at 35^oC, and the lowest rate was at 5^oC.

In conclusion, as the temperature increased the rate of inactivation increased, and for Staphylococcus aureus and E.coli, 35^oC was the optimum temperature for inactivation by thermal-chemical disinfection.

References

Fraise A, M. K., & Ayliffe, G. J. 2000. Control of Hospital Infection: A Practical Handbook, 4th Edition. Arnold: London.

Fraise, P. A., Lambert, & Maillard, J. Y. 2003. Principles and Practice of DIsinfection, Preservation and Sterilization, 4th edn. Blackwell Science: London.

Gardner, F. J., & Peel, M. M. 1998. Sterilization, Disinfcetion and Infection Control, 3rd Edition. Churchill Livingstone: Edinburgh.

Knight, D. J., & Cooke, M. 2002. The biocides business: regulation, safety and applications. Wiley-VCH: Weinheim.

Asbestos is one of the naturally occurring minerals, which has a fibrous structure. Hallenborg and Stewart (2003, p. 56) define asbestos as Naturally occurring fibrous material that has been a popular building material since the 1950s. The two definitions show that this is a fibrous mineral that is popularly used in construction. Asbestos is always used in making construction materials because of its ability to withstand high temperatures. Constant exposure to asbestos may have serious negative impact on the health of an individual. According to the research by Kaminsky and Campbell (2010, p. 45), exposure to asbestos among construction workers is accountable for over 4500 deaths in the United States alone.

Route of exposure and fate in target organ

Asbestos is very popular in construction because of its ability to withstand high temperatures, which makes it one of the best insulators. The roofing shingles, floor tiles, ceilings, asbestos cement, and some paper products are some of the common materials that are rich in asbestos. Other products include automobile brakes, transmission parts and the clutch. Heat resistant fabrics, gaskets, coating materials, and packaging materials are also made using asbestos. It means that although they are commonly found in the construction materials, there are various other products- other than construction materials- that are rich in asbestos. Using any of these materials is a route of exposure to this dangerous mineral. However, it is important to note that the degree of exposure will directly depend on the condition of these products when one uses them. According to Amaducci (1986, p. 58), exposure to asbestos will be high in products that are wearing out. For example, when one is exposed to a building material that is wearing out such as iron sheet, then the dangers of exposure to the mineral will be high. Another common route of exposure is on the construction sites where people have to hit or heat the materials. The process of heating or hitting these materials may expose one to the mineral. The diagram below shows the route of exposure to asbestos.

Route of Exposure

Breathing of asbestos causes asbestosis to the lungs, which may ultimately lead to lung cancer if not treated in time. Schreier (1989, p. 46) observes that prolonged exposure to asbestos fibres may lead to lung cancer. The fibre is also very dangerous to the respiratory track when one inhales it for a prolonged period.

Adverse effects

According to Oberta and Oberta (2005, p. 34), people who work in the construction sites and those dealing with old materials made with asbestos fiber are at greater risks of getting adversely affected by this mineral. Although many people are always exposed to asbestos within the natural environment, the above professions will subject an individual to a prolonged period of exposure to it. Lung cancer is one of the most common effects of prolonged exposure to the asbestos. When one breathes this compound for a long time, it will thicken the walls of the lungs leading to the lung cancer. Mesothelioma, a fatal health condition, is another common health complication that may arise out of the constant exposure to asbestos. Schreier (1989, p. 34) also notes that moderate exposure to asbestos may lead to asbestosis. Inasmuch as asbestosis is not fatal, it destabilises the body system, which may lead to other serious infections that may be fatal. Diffuse pleural thickening is another health complication that is very common among the construction workers who are always exposed to asbestos on a regular basis. It is important to note that all the above mentioned adverse health consequences always take some time before they can manifest in the body. It means that an individual can work at high risk areas for years without realising that he or she is being exposed to asbestos. By the time the disease manifests itself in the body, the damage is already at its advanced stages.

Possible modes of action

It is a fact that the asbestos is still one of the most preferred construction materials because of its high resistance to heat and its strength. It is also popular in packaging of various products. However, it is important for the responsible stakeholders to ensure that the users of these products and those who are involved in the construction are protected from their harmful effects. There are some possible modes of action that should be observed to ensure that people are protected. One such action would be to ensure those construction workers, and all other people who work in places rich in asbestos have protective gears that would ensure that they do not breathe in this dangerous compound. The diagram below shows workers handling materials rich in asbestos wearing proper protective gear.

All products manufactured using asbestos should also be given an expiry date so that they can be replaced before they start releasing large amounts of asbestos among the users.

Legacy and possible consequences of continued use in developing countries

There is a legacy in the use of asbestos in the construction industry in the developing countries. According to Castleman and Berger (2004, p. 12), most of the construction companies in the developing countries prefer the material when developing glasses and other construction products. Most of their workers are rarely given proper protective wears when they are at the construction sites. It means that they will be exposed to asbestos for a long time, and this would consequently lead to some of the health problems mentioned in this paper.

List of References

Amaducci, S 1986, Asbestos: Directory of Unpublished Studies, Spon Press, London.

Castleman, B & Berger, S 2004, Asbestos: Medical and legal aspects, Aspen Publishers, New York.

Hallenborg, M & Stewart, M 2003, New York landlords law book, Nolo, Berkeley.

Kaminsky, A & Campbell, K 2010, The lawyers guide to lead paint, asbestos, and Chinese drywall litigation, American Bar Association, Chicago.

Oberta, A & Oberta, A 2005, Asbestos control: Surveys, removal, and management, ASTM International, West Conshohocken.

Schreier, H 1989, Asbestos in the natural environment, Elsevier, Amsterdam.