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.
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
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.
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.
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.
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.
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?
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.
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.
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.
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?
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.