Sunday, December 7, 2008


Escherichia coli is normally a benign gram negative bacterium, found in the lower intestines of warm blooded creatures including humans and often considered beneficial because of its ability to synthesize Vitamin K2 and keeping out pathogens from the body. The famous pediatrician and microbiologist Theodor Escherich of Germany, after whom the bacterium has taken its name, might never have thought, when he discovered it in 1885, that this ubiquitous organism would play a vital role in human health one day. A new born child gets E.coli within 40 hours of its birth through water, food and the persons handling it. There are 700 stereotypes of E.coli identified so far and a few of them can be virulent in causing serious food poisoning. For food scientists E.coli is a critical marker for assessing the microbiological safety of foods and its presence in water or foods is taken as indication of contamination with fecal matter and consequent possibility of presence of pathogenic organisms. Unhygienic food preparations, farm contamination due to manuring, irrigation of crops with contaminated water or raw sewage, all can result in food contamination with unpredictable adverse consequences. Raw ground beef which finds many use in processed foods, raw seed sprouts, spinach, raw milk, unpasteurized juice and foods handled by unhygienic workers under insanitary conditions will invariably be contaminated with E.coli and such foods can pose risks to consumers.

Virulent strains of E.coli include O157:H7 and O121:H19 capable of excreting Shigatoxins, similar to toxins from Shigella; there are also others like O111:B4, O104:H21 etc which are not as dangerous as them. A pin head can hold about 2.5 lakh cells of these microbes, as they are hardly 0.5-2 microns in size and just about 10-50 cells can be fatal to a child or old age person if not treated properly. An estimated 1 lakh cases of human infection with E.coli O157:H7 are reported annually in the Americas with 2-7% developing serious haemolytic uremic syndrome (HUS) causing damage to kidney, intestine, liver and pancreas, eventually leading to coma. 5% of HUS patients, mainly children and old folks die because of higher sensitivity to the toxins. 44 million pounds of beef were recalled in 25 episodes of contamination in the year 2007 alone in USA. The economic burden in treating the affected population is estimated at $ 400 million per year. Why no cases have been reported from India is a mystery though the traditional cooking habits and shunning of cold foods like salads could be the main reasons. Or could it be that such cases are not diagnosed properly and therefore go unreported?.

Cows are known to carry E.coli 0157:H7 but they do not get sick due to their presence in their guts. Contamination usually takes place through contact with cow dung. The cells get attached to the mucus walls of the GI tract and they are regularly shed along with the excreta. The severe damage potential of this pathogen attracted attention of the scientific community and a vaccine has since been developed in Canada being marketed under the brand name Econiche for use amongst the cattle reared in open as well as in restrained environment. The vaccine has already been approved for unrestricted use in Canada and USA for immunizing beef and dairy cattle which significantly reduces shedding of E.coli O157:H7 cells into the environment and consequent lesser risk to human health. Effectively the vaccine prevents the cells of the microbe from attaching to the intestine of the cattle, thereby reducing their reproduction within the animal.

Can E.coli O157:H7 be a serious health hazard ever in India? A difficult question considering that millions of domesticated cows live happily with the human beings at close proximity and cow is an integral part of the rural economy. Either Indian cows do not harbor this virulent type in their body or Indians must have developed high degree of immunity to them over years of close contact and personalized rearing system. Or the habit of Indian population to eat mostly well cooked hot foods and drink boiled milk might be preventing wide scale occurrence of E.coli infection. Or the E.coli strains present in Indian cattle are highly resistant to mutation into virulent forms under Indian conditions and feeding regimen. Nonetheless it is prudent to put in place a national monitoring system, probably under the aegis of National Dairy Research Institute/Indian Veterinary Institute under the ICAR so that the country is well prepared to manage such an epidemic if and when it occurs.


1 comment:

Lakshmi Bharadwaj said...

Illuminating, sir! I never knew E Coli could be dangerous! Had just assumed it to be this sleepy microbe born to help us! I do think something needs to be done to monitor Indian Cattle though, as you have said, since the thought of some sort of epidemic or disease is scary!