(iv) the product is either served cold or reheated insufficiently to kill
the vegetative cells. Some of the ingested cells survive through into
the small intestine where they sporulate and produce enterotoxin.From the above outline it is clear thatC. perfringensfood poisoning is
more likely to occur where food is being prepared some time in advance
of consumption and that adequate refrigeration is the key to its control.
Most cases ( 4 70% in the United States and 4 87% in England and
Wales) are associated with meat products such as stews, meat gravies,
roast joints and pies. This is partly due to the frequent association of the
organism with meats, but major contributory factors are the low redox
potential, mode of preparation and consumption which can give
C. perfringensthe opportunity to multiply to dangerous levels.
Cured meats are rarely involved inC. perfringensfood poisoning. This
is a fine example of the hurdle concept in action (see Section 3.4);
individual preservative factors such as salt content, nitrite level and heat
processing are insufficient on their own to assure safety but effectively
control growth ofC. perfringensin combination.
Most outbreaks occur in connection with institutional catering such as
schools, old people’s homes and hospitals. The association between
C. perfringensand hospital food in particular goes back a long way, to
the outbreaks at St. Bartholomew’s Hospital in the 1890s, but here at
least there are signs of progress. In the UK, the 1991 Richmond Report
on the safety of food noted that outbreaks in hospitals fell from a peak of
more than 20 per year in the 1970s to about half this number in the 1980s:
a decline attributed to improvements in facilities and staff training.
7.7 Enterobacter sakazakii
7.7.1 Introduction
Enterobacter sakazakiiis an emerging opportunistic pathogen associated
particularly with sporadic life threatening infections in low birth-weight
infants, though it can cause disease in all age groups. The first recorded
cases occurred in 1958 in Europe and the United States. Up until 2005
there had been about 75 cases of Ent. sakazakii infection reported
worldwide. In many cases, particularly those reported up to the mid-
1980s, the source of the infection was unknown but in more recent years
contaminated infant milk formula has been recognised as the principal
source of the organism in clinical infections.
7.7.2 The Organism and its Characteristics
Enterobacter sakazakiiis a Gram-negative, motile member of the Enter-
obacteriaceae. It was originally classified as a strain ofEnterobacter
214 Bacterial Agents of Foodborne Illness