Food contaminated with Shigella bacteria
Good food, bad food debate
By D.C.Hettiarachchi (M.Sc. in Industrial Microbiology)
The recent death of a child by consuming sausage contaminated with Shigella bacteria prompted me to write this article to share my knowledge with fellow readers.

Shigella bacteria is a member of the notorious family of bacteria known as Eneterobacteriaceae and is closely related to Escherichia coli commonly known as E.coli, which is the most common bacteria in the gastrointestinal tract of man and many other animals. Genus Shigella consists of four species; Sh.dysenteriae (subgroup A), Sh.flexneri (subgroup B), Sh. boydii (subgroup C), and Sh. sonnei (subgroup D). All species of Shigella are pathogenic to man causing bacillary dysentery of varying severity.

Shigella are found only in the intestinal tract of man and other primates, or in materials contaminated with faeces of man and primates. Shigella are host adapted and cause illness in other primates and not pathogenic to other animals. Person to person transmission via oral route or waterborne transmission is the main route of infection. Susceptibility to Shigella infection is found among old, the young and those with an underlying disease. Exposure to shigellas mostly happens in places where hygiene is poor, ambient temperature is high and disease is endemic. Travellers of countries of higher hygiene standards are at greatest risk.

Asymptomatic carriage of Shigella may persist for several months following recovery from symptoms and is a factor on the spread of Shigellosis. Shigella is acquired from man. In cases of food borne transmission, this means contamination of food which is not to be cooked before eating either from sewage contaminated environmental source such as water or soil or from an infected or carrier food handler. In places where hygiene is poor, both sources of contamination are important. Salads which may be grown in contaminated soil or washed in contaminated water or prepared by an infected food handler are higher risk items along with drinking water and ice cream.

Any food which is not heated directly before consumption, handled by a Shigella infected person with poor personal hygiene, is a potential vehicle of food borne shigellosis. All species of Shigella have optimum growth temperature of 37oC and they are readily destroyed by heating at 63oC for 5 minutes.

As Shigella bacteria is found only in the gastrointestinal tract of man, any human faecal contamination is a potential source and washing hands thoroughly (rubbing hands with soap for at least 15 seconds) before preparing food could greatly reduce such contamination.

Coming back to the case of shigellosis which cost the life of a child, has the MRI identified the species of Shigella bacteria involved in the present case? Now knowing the source, has the relevant authority traced the processing plant that produced that particular batch of sausages? Has MRI a data base which includes the names of Shigella species involved in earlier cases and the locations?

Eggs covered with poultry dung?
At the seminar on food safety organised by the SLAAS in Colombo a few weeks ago, Professor Dulitha Fernando from the University of Colombo, is reported to have said that bad meat, poultry, milk or eggs have been found to be the main sources of food poisoning in Sri Lanka.

She is also reported to have said that intestinal infection has been ranked the seventh leading cause of hospital admissions in Sri Lanka. I do not know about bad meat and poultry because I don’t eat any kind of meat. But I am a consumer of eggs and I do believe that everyone knows about the sad state of affairs with regard to the sale of eggs in Sri Lanka. There is hardly a place where you can buy clean eggs except in some supermarkets.

In ordinary village boutiques, the eggs which are for sale are covered with poultry dung which, I believe is a carrier of the salmonella bacteria. Newspapers, off and on, carry reports of sellers of such eggs being hauled up before courts by duty –conscious public health inspectors (PHI). But such cases are few and far between. The majority of the public health inspectors are either in the pay of the poultry producers or quite unconcerned about their duties to the citizens of the country, who, pay their salaries.

There is an association called the Poultry Producers’ Association, which is often vociferous when governments try to take steps to stabilise the prices of poultry products. But what measures have they taken to educate the poultry producers, specially the small time ones, about the necessity to ensure the hygienic quality of the eggs that are put out for sale by these producers?

Absolutely nothing. It is also time that our energetic Minister of Health galvanises his public health safety officers, particularly the PHIs to apprehend the errant sellers of contaminated poultry products without their being confined to their offices day in day out expecting solutions to fall into their laps through approval of building plans etc, the most lucrative sideline of their business, in these happy days of the boom in building activities. One of the ways to avoid contamination is to wash the eggs with soap and water before use.

Concerned citizen

Back to Top  Back to Business  

Copyright © 2001 Wijeya Newspapers Ltd. All rights reserved.