Principles of Environmental Health - Research Paper Example

College of health science Principles of Environmental Health Mr English David Christopher Murray Escherichia coli O157:H7 Bacteria are a huge group of single cellular microorganisms known as prokaryotes. Prokaryotes are collection of organisms whose cell has no nucleus and are mainly unicellular. Bacteria are just a few micrometers long in size and on the basis of shape are classified in three basic groups: cocci, bacilli, and spirochetes. The cocci are rounded, bacilli are rod like in shape, and spirochete are spiral shaped. Some bacteria are pleomorphic, which means that they are variable in shape and can change their shape (Levinson 2008). Not all the bacteria are harmful some bacteria are harmless or even beneficial. They can help in promoting good health, some digestion and some serve medicinal purposes. Lactobacillis is a family of bacteria found in the human digestive tract. Acidophilus is a member of lactobacillis and it is the best known bacteria of this family aiding in the breakdown of lactose to lactic acid and also the breakdown of other sugars. The production of lactic acid in the body provides acidic environment in the body which can inhibit the growth of harmful bacteria. Acidophilus is also used in certain drugs. Bifidobacteria is also a beneficial group of bacteria and is present in the human digestive tract and helps in digestion as well as ; it has also shown some anti-tumor qualities. Some bacteria are beneficial in other ways like they are used in agriculture for plant growth and some are used for cleansing of water. (Jeremy & Simon 2004). Escherichia coli (E. coli) are bacteria referred to as an enterobacteriacea, that is they exists normally in the intestine of human and animals. This bacteria exists in the form of gram negative rods and is named for the man, who discovered them, Theodor Escherich, in 1885. E. coli has been associated with many pathological conditions which include the inflammation of the gall bladder, inflammation of the biliary tract, infections of the urinary tract and blood, as well as diarrhea, particularly traveler’s diarrhea. Newborns are also affected and typically present with inflammation of the meninges. Though this inflammation has also been reported in adults but it is more common in new born children and it usually occurs in adults as a result of invasive procedures. The respiratory tract might also be involved with resultant pneumonia. E. coli infection stem from various different sources: E. coli are present in patient’s own colonic flora; E. coli causing neonatal meningitis are present in mother’s birth canal; and those that causes traveler’s diarrhea are present in food or water (Levinson 208; Warren 2008) E. coli is a considered aerobic bacteria, though not completely aerobic. They can survive in the presence of oxygen and it also has the capability to exist in the absence of oxygen, anaerobic, by the process of fermentation. E. coli also has the property of movement though there are certain forms of the bacteria that form exceptions and do not move. The mobility is provided by flagella, which are referred to as peritrichous flagella, present on all sides of the bacteria. The bacterium does not have the property of forming spores; and has three antigens present. The antigen present on the cell wall of the bacteria is the “O” antigen, the antigen present on the flagellum is the “H” antigen, and finally the antigen found on the capsule of the bacteria is the “K” antigen. These antigens have great variability with each of them existing in many different forms. This is the reason that E. coli exists in many different forms. This bacterium is responsible for infections of the urinary tract in 50 percent women in the United States. This is because there is a greater disposition towards females of this infection owing to the increased hospital visits related to deliveries and their higher susceptibility during the child bearing period. But this pattern is different for the newborns in which the rate of the infection of the urinary tract is higher in male children than in females. E. coli is also listed as an infection which occurs in the hospital settings and has been associated with an average of 31 percent hospital acquired infections in the United States as well as a cause of diarrhea in 4 percent of the people. The meningeal inflammation that results due to E. coli should not be overlooked because it accounts for 8 percent of the deaths due to this condition and it can also result in pathological conditions of the nervous system (Ramana 2004; Warren 2008). The E.coli can cause diarrhea, urinary tract infections, sepsis and meningitis. The diarrhea that occurs due to the E. coli is caused by four classes of this bacterium which function in different ways. The first one is the Enteropathogenic E. coli that affect usually infants below the age of two years and hence occurrences are mostly reported from maternity homes. This group of E.coli has the capability of binding to the cells of the intestine and destructs its microvillus which leads to diarrhea. The spread occurs through the consumption of water or via the food that infants consume (Levinson 2008; Stephen et al 2004). The next group of E. coli is Enterocytotoxigenic E. coli. This group is the major cause for traveler’s diarrhea in all age groups. It produces exotoxins which are known as heat labile and heat stable exotoxins. They have an effect on adenylate cyclase and guanylate cyclase respectively. These enzymes lead to a cascade of reactions which cause retention of fluid and electrolytes with the passage of the intestine. This is turn results in diarrhea. The cause for this infection is also via the dietary intake. The world health organization has reported that this group of E. coli accounts for a mortality rate which is very high that is 380,000 deaths and 210 million people suffer from this infection every year (Levinson 2008; Stephen et al 2004). Enteroinvasive E. coli as the name indicates is a strain of E. coli which takes over the cell and it also has the capability of moving ahead from one cell to another. It enters a cell by endocytosis and within the cell it replicates and starts spreading to other cells. Contaminated water, cheese and human contact are the ways of its spread. The patient presents with mucus or blood in stools, high body temperature and discomfort in the abdomen. This dysentery caused by enteroinvasive E. coli accounts for the mortality of 500,000 children in the developing nations of the world every year (Levinson 2008; Stephen et al 2004) The last group is the enterohemorrhagic E. coli. This strain of E. coli is responsible for the production of verotoxin which is an exotoxin. This produces toxigenic effects for the colonic cells. According to a report of the Centers for Disease Control and Prevention, each year 70,000 people are affected by this strain of E. coli. This strain spreads from the ingestion of beef that has not been cooked completely and properly. This toxin can lead to a halt in the formation of proteins by disrupting the RNA. This can lead to inflammation associated with bleeding in the colon. It can also result in a fatal condition which is known as hemolytic uremic syndrome. This condition occurs when the verotoxin enters the circulation of a person. It has been further discussed later in this essay. (Robbins et al 2005; Ramana, 2004; Levinson 2008; Stephen et al 2004). The E. coli bacteria can also affect the urinary tract resulting in urinary tract infections. The sign and symptoms include hematuria, dysuria, urinary frequency and pyuria. Hematuria is the presence of red blood cells in urine and it is also known as hemoglobinuria because hemoglobin is a the most important component of red blood cells. Dysuria means difficulty in urination and pyuria means pus in urine or white blood cells in urine. When there are 4 or more neutrophils present in the urine then the condition is called pyuria. The pili of E. coli bind to the cells of the urinary tract and lead to these infections. These infections can be restricted to the lower urinary tract and they also have the ability to move up towards the kidneys and lead to renal infection (Levinson 2008) E.coli can also spread into the blood and lead to septic shock in a person and especially newborns are more prone to E. coli sepsis because they lack IgM antibodies. This spread can also lead to a raised body temperature and hypotension. The bacteria E. coli also causes meningitis chiefly in infants. Antigen K1 is present in 75% of the E. coli bacteria discovered that causes meninigitis and the antigen cross reacts with B carpuscular polysaccharide. However the antigen K1’s virulence mechanism is not understood. These symptoms of E. coli infections take 48 to 96 hours to develop mostly but sometimes they may take one whole week to appear (Levinson 2008). E. coli O157 is a strain of E. coli bacteria that is enterohemorrhagic, it causes bloody diarrhea. This strain of E. coli is present in cattle and undercooked meat. This essay discusses E. coli O157 strain in accordance to its effects, treatment, prevention and its outbreak all over the world (Ramana 2004; Stephen et al 2004). Enterohemorrhagic Escerichia coli (EHEC) O157:H7 is the full name of the bacterium E. coli O157 which is a food and waterborne pathogenic strain of bacterium E. coli. The bacteria E. coli O157 was first known as a result of gastrointestinal illness in the early 1980s. E. coli O157 is different from other pathogenic E. coli in different ways like , E. coli O157 is sorbitol negative whereas 93 % of the E. coli ferment sorbitol, E. coli O157 does not produce heat stable toxin but some type of E. coli do produce it, E. coli O157 cannot hydrolyze 4-methylumbelliferyl -β-D-glucuronide while other strains can. The E. coli O157 strain is most closely related to K12 strain, as they share a common backbone. These two strains are just about identical in gene sequence and also in length, but O157 at one specific point the base pairs of genes are reversed. There are hundreds of sections of DNA in each genome, 1.34 megabases code for 1,387 genes in the O strain called O islands and 0.53 megabases code for 528 genes in the K strain known as K islands. The O157 strain only has 40% of the acquired genes, meaning 561 of 1387 genes can be assigned a function. There are 3574 protein- coding regions in the backbone and the average nucleotide identity is 98.5% between O157 and K12 (Perna 2001; Ramana 2004). E. coli O157 is also a water-borne strain which can also be found in water. Usually the source from where the water is contaminated by the bacteria E. coli is animal waste and sewage connection. This animal waste and sewage connection already consists of the bacterium and may infect the whole supply of drinking water to human beings. Prevention strategies have thus been formulated to check the level of contamination of water supply. Laboratory diagnosis can be carried out to check if water is contaminated with the bacteria or not. The contaminated water can be purified by killing the E. coli present in the water. The purification of the water can be done by treating the water with chlorine or ultraviolet light (Ramana 2004). E Coli O157:H7 is a strain which cannot cause illness in the animals but can cause them to be carriers of the bacteria. It has been found that this strain is usually transmitted into human beings via the animals who are affected by this bacterium. This strain of E coli can be found in cattle, sheep, pigs, deer, dogs and poultry. In order to find out as to which animal has this strain, their feces can be tested which would show a positive sign of this bacterium. Animals particularly catch E. Coli O157:H7 by consuming the bacteria which is found in the feces of the infected animals. Anything which would be affected by this bacterium may cause the strain to enter the animal’s body which can then act as a carrier. It is believed that E.Coli O157:H7 does not cause any apparent illness or defect in the animal upon which it acts. Moreover the effect on animals can be minimized if the animals are given proper care and are kept away from contaminated feces and water. If the strain is not ingested by the animal from any source then the animal will not act as a carrier for this strain (Todd 2007).  E. coli has different components giving it the propensity to cause diseases; these are; pili, capsule, endotoxin and three exotoxins. Out of the three exotoxins, two causes watery diarrhea and the other causes bloody diarrhea. When a person has food poisoning from E. coli, the first step is the attachment of the bacterium to the jejunum and ileum of the small intestine in human gastrointestinal tract, with the help of pili which are the outgrowths from the bacterial surface. Once attached to the gastrointestinal wall, the bacteria synthesize exotoxins which will act on the wall’s cells and will cause diarrhea. The bacterium E. coli can produce either of the two enterotoxins, the heat-labile toxin and heat-stable toxin. The heat-labile toxin act when the enzyme adenylate cyclase is stimulated. The addition of adenosine diphosphate-ribose to the G protein stimulates the cyclase which in turn activates the heat-labile toxin and the result will be the increased intracellular cyclic adenosine monophosphate concentration. Further this high intracellular cyclic adenosine monophosphate concentration stimulates the cyclic adenosine monophosphate-dependent protein kinase, which has the ability to phosphorolate the membrane ion transporters. The transporters take ions out of the cell which causes the outburst of fluid, calcium and potassium to the lumen of the gastrointestinal tract ensuing watery diarrhea. EHEC strains of are invasive, invading, the large intestinal epithelium causing bloody diarrhea. E. coli O157 produces exotoxin known as verotoxin, which acts by removing an adenosine from ribosomal RNA (28S), thus inhibiting protein synthesis (Sheff 1999; Levinson 2008). Some people who suffer from bloody diarrhea caused by E. coli O157 can also suffer from a syndrome known as hemolytic-uremic syndrome. This syndrome occurs because of the entrance of the exotoxin known as verotoxin into the bloodstream. In this syndrome the patient suffers from hemolytic anemia, thrombocytopenia and renal failure. Anemia is a condition in which the patient’s blood is deficient in red blood cells or hemoglobin so hemolytic anemia is that anemia which occurs due to the breakdown of red blood cells. The endothelium of the small blood vessels contains receptors for vertoxin. When the vertoxin enters the bloodstream it binds to the receptors present on the surface of the endothelium. The vertoxin will then destroy the endothelium to which it is attached and will cause hemolysis which means breakdown of red blood cells and release of hemoglobin from red blood cells. When red blood cells pass through these damaged blood vessels the red blood cells get distorted and at last lysis occurs. Thrombocytopenia refers to platelets deficiency in blood. In hemolytic uremic syndrome the patient suffers from thrombocytopenia because the platelets adhere to the already destroyed epithelium by vertoxin. Eventually the amount of functional platelets diminishes causing thrombocytopenia. The surface of the epithelium of kidney also has the receptors for vertoxin and by binding with the receptors, vertoxin destroys the kidney epithelium. The destruction of kidney epithelium leads to acute renal failure (Levinson 2008; Ramana 2004 Stephen et al 2004). In 2006, biggest food-borne diseases were spread in Canada by the fresh spinach contaminated with E. coli. More than 200 people got sick and three deaths occurred and 31 cases of hemolytic uremic syndrome were reported. The causes of the diseases were contamination of the spinach and the environmental risk factors for the contamination were the presence of pigs in the nearby areas, and surface waterways exposed to feces from cattle. And the precise way by which the spinach got contaminated still remain unknown because the spinach was contaminated before the investigation started (E. coli cases down in 2009, CDC says; Todd 2007). Another example of an outbreak of E.coli, 2 people died and 28 fell ill during spread of a strain of E. coli in ground beef, three of them developed kidney failures. However recently it has been found that the cases of E.Coli have decreased in number because of increased preventive measures. A report by CDC has shown that cases of the E.Coli strain which were previously very common in states were reduced in number from their previous infections. A 12% decrease in the number of infections has been noticed since 2008 (Money Times 2010). The pathologic conditions that result due to E. coli are treated differently according to their specific requirements. In an infection of the urinary tract which is not very complicated can be treated by keeping the patient on antibiotics particularly penicillin which should be administered orally for a time duration of just one day to as long as three days. In the case of infection of blood by the bacteria injections of third generation antibiotics are administered. This includes a combination therapy of a cephalosporin with an aminoglycoside. In the case of meningeal inflammation in new born, penicillin along with a cephalosporin is the suitable treatment. A loperamide and symptomatic treatment which mainly focuses on providing the patient with fluids is mainly done in the diarrhea which occurs due to this bacterium. The diseases caused by the bacterium E. coli O157 cannot be cured by any treatment. The diarrhea caused by E. coli O157 cannot be treated by antibiotics, like ciprofloxacin, because these antibiotics increase the amount of vertoxin in turn increasing the risk of hemolytic-uremic syndrome. The best option for the patients suffering from diarrhea caused by E. coli O157 is to drink plenty of water and other fluids which would replace the electrolytes in the body to normal levels. Individuals most at risk from the bacteria E.coli are under the age of five or are above 60. People suffering from severe illnesses such as AIDS can also suffer because of this bacteria ( NIH 2009; Tarun et al 2009). Vaccination for infections caused by E. coli does not exist but measures can be taken to prevent the occurrence of disease states associated with this bacterium. The water lines that are serving the purpose of supplying water that is used for consumption should be tested for the presence of bacteria. The presumptive coliform test is performed for checking the infiltration of water by feces and the coli levels according to this test should have a higher value tan 3 in a sample of 100 ml. The milk should also be examined and tests to check the presence of bacteria should be seen. In the hospital setting it should be made sure that those patients who are catheterized are given antibiotics prior to the process so that their chances of acquiring urinary tract infections are lowered. If patients who are on intravenous drugs or medications get infections again and again, these should also be removed. The cranberry juice contains tannins which have the ability to inhibit the binding of pili of that strain of E. coli which causes urinary tract infections to the urinary bladder epithelium. So the cranberry juice is used for the prevention of urinary tract infections. A person who gets traveler’s diarrhea should take medications like doxycycline in advance so that he cannot get infected. It should also be ensured that one is on a healthy diet which includes food that is properly cooked and water that is clean and these precautions should particularly be taken when travelling to areas where bacterial infections are common. (Ramana, 2004; Levinson 2008; Sheff 1999). In laboratory E. coli can be easily cultured on the nutrient agar as well as the Mac Conkey agar and the Eosin methylene Blue agar. They provide with grey, bright pink and metallic sheen colonies on the agars respectively. The most feasible temperature for E. coli is 37 degrees. Some of the E.coli strain forms lactose and if this lactose containing bacteria ferments then it would give a pink color with the Mac Conkey agar. While the ones which do not form lactose give a colorless result. It is seen that the bacteria gives different colors in different mediums. With EMB agar, the bacteria E.Coli gives a green sheen color. In laboratory diagnosis it is very important that the tests are able to differentiate between different bacteria. The characteristic feature which differentiates the E.coli bacteria from other lactose fermenting gram rods is its ability to produce the indole ring from the amino acid Tryptophan. Other than that it also has the characteristics of decarboxylation as it has the ability to decarboxylate the amino acid Lysine. E.Coli only uses acetate to produce carbon whereas other bacteria also have other sources to produce carbon. E.Coli O157:H7 does not have the ability to form the alcohol known as sorbitol whereas other bacteria do have the ability to form it. All these together can help to differentiate between other bacteria and E.Coli in laboratory diagnosis. If a human being is suspected to have this bacteria then majority of the tests are carried out on the stools. These stools show a positive sign of the bacteria if it is present in the human subject (Levinson 2008). E.Coli O157 is one of the deadliest strains of the bacteria. Different characteristics of this strain make it difficult for diagnosis and treatment. It is spread through animal carriers which are very difficult to be pinpointed as animals can catch the bacterium from many different sources. The outbreaks of this strain have reported to cause many illnesses in recent years and different treatment strategies have been formed in order to cure individuals who have consumed this bacterium. The mechanism of how O157 acts, mentioned above may be a breakthrough in the treatment strategies of the bacterium. The outbreaks of the E. coli O157 can also be controlled if strict measures regarding the feeding of animals are taken as the strain spreads only through feces and substances which have been contaminated previously. The strain has been widely studied upon and effective strategies to combat the diseases caused by it are underway! (Todd, 2007). 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