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The investigation of cases of food poisoning or suspected food poisoning absorbs
much time and effort and places a heavy burden of work on the Public Health Laboratory
Service. Only two outbreaks were of any size; 47 cases in a Teachers' Training
College and 196 cases in a factory. Generally all the persons affected or concerned
in food poisoning incidents are only too willing to co-operate in our investigations
but this was not so at one factory. This gives rise to difficulties and hampers
action as is shown by the following three food poisohing incidents at this factory:-
Incident 1 - On 7th October 1954 notice of an outbreak of food poisoning was
received. Enquiries at the factory on that date showed that 18 members of the night
shift had suffered from diarrhoea, nausea and abdominal pains about noon on 5th
October. A few of the affected persons stated that they had felt out of sorts on
arriving home from work on the morning of 5th October.
All the affected persons had consumed stewed steak in the works' canteen at
midnight on 4th October. The stewed steak had been prepared that morning and served
at midday to approximately 400 persons, none of whom complained of any ill-effects.
The remainder of the stewed steak had been kept till evening when, after the addition
of two tins of steak, it was heated for the nightshift, None of the midnight meal
was available for examination.
The hygienic condition of the premises, equipment and stores was satisfactory.
All the affected persons were asked to provide specimens of faeces, but were reluctant
to do so as they had all recovered fully. In general the attitude of the canteen
staff was antagonistic, but after a talk by the Sanitary Inspector on the purpose of
the investigation specimens were supplied by 13 of the 21 members of the Canteen staff
on 9th to 12th October. No food poisoning organisms were found.
This outbreak appeared to be due to contamination of the stewed steak and the
opportunity for growth of an organism provided by the cooling and reheating. The
delay in getting faecal specimens reduced the chances of finding the germ.
Incident 2 - On 18th August, 1955 another outbreak of food poisoning was reported
Enquiries at the factory on that date showed that 69 were affected. All had taken
lunch at the canteen on 17th August and the only food consumed by all was roast beef
and gravy. The roast beef had been cooked on 16th August and reheated on 17th
August. The gravy had been prepared from the fat obtained at the roasting of the
beef on 16th August. The onset of symptoms ranged from 8 to 14 hours after the
consumption of the suspected food.
Samples of the roast beef and of two other items of the midday meal on 17th
August were obtained for bacteriological examination. No food poisoning organisms
were found, but all specimens showed the presence of bowel germs. Only two of the
canteen staff provided faecal specimens and the report on these was negative.
This outbreak appeared to be due to the contamination of the food by bowel
organisms and the opportunity for their growth provided by the cooling and reheating.
The probable source of the contamination was reported and the non-cooperation of the
canteen staff in the investigations discussed with the personnel manager and the
works medical officer.
Incident 3 - On 22nd September, 1955, notice was received that a large number of
employees were suffering from food poisoning. A visit to the factory showed that
some 50 persons had reported at the works medical centre that morning suffering from
diarrhoea, vomiting, fever and collapse to a varying degree. Some 20 persons after
being seen by the works medical officer were sent home by car. The onset of symptons
lay between 1 a.m. and 5 a.m. on 22nd September.
Preliminary enquiries showed that all the affected persons had consumed roll and
dripping served during the morning break on 21st September, but only a few had taken
lunch at the canteen on that day. The dripping had been obtained from roast beef
cooked on 19th September and- thereafter stored in the larder. None of the dripping
or of the items of the midday meal of 21st September was available for bacteriological
examination.
Arrangements were put in hand to obtain specimens of faeces from the canteen
staff and from the affected persons. Some of the affected persons resided outside
the Borough so the assistance of the Medical Officers of Health of the districts
concerned was sought for obtaining specimens. On the morning of 23rd September
specimens had been provided by 4 affected persons and 8 of the 22 members of the
canteen staff. A talk was given to the canteen staff on the severity of the outbreak,
on the importance of full investigation and the need for their full co-operation.
As a result of this a further two faecal specimens were obtained and 12 of
the staff permitted throat and nose swabs to be taken. On 26th September 4 more
specimens were provided by the canteen staff. On that afternoon the laboratory
reported that, though no pathogenic organisms had been found in the throat and nose
swabs, salmonella typhi-murlum (a food poison germ) was present in some of the faeca
specimens. On the same day telephone messages about the presence of this germ in
faecal specimens were received from some of the Medical Officers of Health whose
assistance had been sought.
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