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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 have different shapes such as cocci, bacilli, and spirochetes. 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 (Jeremy & Simon, 2004).
Many of the emerging pathogens nowadays are waterborne i.e. they take birth in water. These can be either a bacteria, protozoa or parasite. Bacteria species can be such as Pseudomonas, Legionella species, Escherichia coli and Vibrio species. These are the most common pathogens (Murray et al, 2009).
Human gets waterborne infectious disease can be caused during water activities, a direct contact with untreated water, drinking, or inhalation of aerosol (Rosen, 2000). One of the reasons that can lead to contamination is the environmental changes such in weather. Storms and heavy rain may result in floods that cause the wastewater to leak contaminating the nearby barrages and water reservoir or even lakes and rivers which are used by people for bathing, drinking and cooking. Also, climate conditions can affect the geographical ranges of the waterborne organisms leading to an increase of human infection cases (Lipp et al, 2002). Cholera has been a known disease in the world. A very 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 the bacterium. 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 -Î²-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. The O157 strain only has 40% of the acquired genes, meaning 561 of 1387 genes can be assigned a function. In the backbone there are 3574 protein- coding and the average nucleotide identity is 98.5% between O157 and K12 ((Perna, 2001) and (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. hemolytic anemia is caused by the breakdown of RBC due to the deficiency in either RBC or haemoglobin. The endothelium of the small blood vessels contains receptors for vertoxin. When the vertoxin enters the bloodstream it binds to these receptors destroying the endothelium to which it is attached and will cause haemolysis. When RBC's pass through these damaged blood vessels the RBC's gets distorted and at last lysis occurs. In haemolytic uremic syndrome the patient suffers from thrombocytopenia because the platelets adhere to the already destroyed epithelium by vertoxin. 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 faeces and the coli levels. According to this test should have a higher value tan 3 in a sample of 100ml. The milk should also be examined and tests to check the presence of bacteria should be seen (Rosen, 2000). 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 traveller's diarrhoea 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 McConkey 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 37oC. Some of the E. coli strain forms lactose and if this lactose containing bacteria ferments then it would give a pink colour with the McConkey agar. While the ones which do not form lactose give a colourless result. It is seen that the bacteria gives different colours in different mediums. With EMB agar, the bacteria E. coli gives a green sheen colour. 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 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 haemolytic 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 faeces 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. These 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 faecal 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 act 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 glycoprotein on the intestinal walls because of which the bacteria adhere to the walls of the intestine. Once the bacteria adhere 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 kinase 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).
Vomiting and watery diarrhoea are symptoms of cholera caused by Vibrio cholerae which can lead to rapid dehydration and death if it isn't treated properly. 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 McConkey. Lactose is slowly fermented in the bacteria because of which McConkey 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). Other methods can also be used such as ELISA and PCR. (Murray, 2005)
The treatment in the case of cholera is adequate infusion of water and electrolytes in the body of the patient. This would balance the 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). Also there are effective types of oral vaccine for cholera prevention at the current time. World health organisation (WHO) has prequalified one vaccine called Dukoral and is licensed in more than 60 countries worldwide. This type of immunisation provides a short term protection, while Shanchol vaccine is a long term protection way. However Shanchol is not prequalification yet by WHO. (WHO, www1)
Control of waterborne pathogens
To eliminate and prevent the spread of cholera and other waterborne pathogens, water supplies, wells, and pools should be disinfected by effective chemicals such as chlorine and an oxidizer or sodium hypochlorite for both disinfection and oxidation that kills the pathogen and keep the water usable. The exposure of the water supplies to ozone and ultraviolet radiation can be helpful. Proper personal and food hygiene are also required (Exner, 2005).
Cases of V. Cholerae
WHO has shown in previous investigations that cases of cholera have risen by 24% worldwide from 2004 until 2008 comparing to the previous years from 2000 to 2004. The latest cholera outbreak that has been reported is in Haiti. In November 2010, the world health organisation WHO has stated that there are 6,742 cholera cases including 442 deaths which were reported by the Haitian Ministry of Public Health and Population. (WHO website)
The waterborne bacteria such as Vibrio cholerae 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.