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).
Many of the emerging pathogens nowadays are waterborne i.e. they take birth in water. Cholera has been a known disease in the world and two emerging waterborne pathogens are Vibrio cholerae O139 and Escherichia Coli (E.coli O157:H7). E.coli has not only become a problem for the underdeveloped nations but has also become a problem for the developed ones. This bacterium would be discussed subsequently. Vibrio Cholerae O139 is a pathogen which first infected many of the people living in Asia. It started in Bengal and then spread to India in 1992 (Ramamurthy et al. 1993, quoted by Sharma et al.2003) from where it entered the vicinities of Thailand. It is through different methods that these emerging pathogens are spreading all over the world giving a difficult time to the authorities who have not handled such cases previously (Sharma et al 2003; Smolinski et al 2003).
Escherichia Coli 0157
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 -I?-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).
Diseases Caused by E.Coli
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 patientaa‚¬a„?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).
Treatment and Prevention
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 traveleraa‚¬a„?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).
Diagnosis of E.Coli
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).
Cases of E.Coli
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).
Vibrio cholerae is the major pathogen belonging to the group of vibrio which causes cholera. Vibrio cholerae are gram negative rods which are shaped like a comma. This bacteria can be divided into two groups in accordance to the antigen present in the cell wall. It is divided into O1 and non O1 respectively. The O1 bacterium always causes an epidemic disease where as the non O1 would may or may not cause a sporadic disease. Vibrio Cholerae is transmitted like E.Coli through contamination of the food or water with fecal material. In human beings this bacteria is either active or in a non active state which may make the individual asymptomatic. Sea animals such as oysters and shrimps carry the bacteria and if they are not cooked enough before eating they may transmit the bacteria to the host (Levinson 2008; Ramana 2004)
Disease caused by Vibrio Cholerae
The bacteria acts on the small intestinal walls where it colonizes itself and secretes enterotoxins. Colonization is a difficult process and to adhere to the intestinal walls the bacteria have to secrete mucinase. This mucinase dissolves the glycoproteins on the intestinal walls because of which the bacteria adheres to the walls of the intestine. Moreover an acidic medium may destroy the bacteria hence people who have taken antacids are more susceptible to the bacteria. Once the bacteria adheres to the walls it secretes an enterotoxin known as choleragen which produces the symptoms of cholera. Choleragen has two subunits known as the A and B subunit. With the help of the A subunit the bacteria is able to catalyze a reaction on the G8 protein. This G8 protein which becomes overly active then produces increased amounts of adenylate cyclise. This adenylate cyclise then activates protein kinases which opens ion channels. This is the major cause of loss of water from the cells as the ions along with them take the water to the lumen of the gut. This would then cause excessive diarrhoea as occurs in cholera. The gene which codes for cholera toxin is the CTX gene (Levinson 2008; Ramana 2004).
Watery diarrhoea is a symptom of cholera caused by vibrio cholerae. It can be diagnosed on the basis of laboratory diagnosis. Stool is cultured which shows the presence of bacteria through colourless colonies of the agar MacConkey. Lactose is slowly fermented in the bacteria because of which MacConkey agar works on it. TSI agar can also be used on it because the bacterium ferments sucrose. TSI agar shows an acid butt without gas when the bacteria is cultured with it (Ramana 2004; Sharma et al 2003).
The treatment in the case of cholera is adequate infusion of water and electrolytes in the body of the patient. This would balance his extracellular fluid and hence the person would not be affected majorly by the bacterium. Antibiotics can also be used in the case of these sporadic diseases. But they would not prove to be much effective when it comes to the destroying the bacteria. It may in some other way enhance the excretion of the bacteria from the body (Sharma et al 2003; Ramana 2004).
The waterborne bacteria such as Vibrio cholera and E.Coli can prove to be deadly if not treated within the specified time. The diseases caused by these bacteria have decreased in the developed countries in comparison to the underdeveloped countries. If certain measures are taken in the underdeveloped countries then the effects of the waterborne pathogens can be decreased even more.