fresh milk do not pose a threat due to the low resistance ofCampylobacter
to conditions of reduced pH oraw.
Other foods recognized as potential sources ofCampylobacterinfec-
tion include shellfish and mushrooms.C. jejuniandC. coliwere detected
in 14% of oyster flesh tested, although 2 days depuration was sufficient
to cleanse oysters artificially contaminated with 800 cfu of campylobac-
ters g^1. An outbreak in the USA was ascribed to raw clams.
7.5 Clostridium botulinum
7.5.1 Introduction
Because of its severity and distinctive symptoms, botulism is the form of
bacterial food poisoning for which we have the earliest reliable reports.
In 1793 in Wildbad, Wurttemburg, 13 people fell ill and 6 later died
after eating Blunzen, a type of sausage made by packing blood and other
ingredients into a pig’s stomach. The sausage had been boiled and then
smoked, after which it was considered stable at room temperature for
several weeks and suitable for consumption without reheating.
Several further incidents ofWurstvergiftung, or sausage poisoning,
were recorded in the years that followed, usually associated with sau-
sages that contained animal components other than muscle tissue. This
prompted a local district medical officer, Justinius Kerner, to undertake a
study of the disease which became known as botulism (Latin:
botulus¼sausage). Kerner noted several important features including
the facts that heating was an essential precondition for the development
of toxicity in sausages and that small sausages or those containing air
pockets were less likely to become toxic.
It was not until 1896 that the micro-organism responsible was isolated
and described by van Ermengem, Professor of Bacteriology at the
University of Ghent and former pupil of Robert Koch. This was a result
of his investigation into an outbreak of botulism where 34 members of a
music club in Belgium ate raw, unsmoked ham. Several noted that the
ham had a slightly ‘off ’ flavour akin to rancid butter but was otherwise
unremarkable. About a day later, 23 of the group fell ill and 3 died within
a week.
Van Ermengem established that botulism resulted from the consump-
tion of food containing a heat-labile toxin produced by an obligately
anaerobic, spore-forming bacillus which he calledBacillus botulinus.He
further demonstrated that toxin would not be produced in the presence
of sufficient salt, that it was resistant to mild chemical agents and was not
uniformly active against all animal species.
Although much of the early evidence suggested that botulism was
confined to meat products, it was later found to occur wherever foods
198 Bacterial Agents of Foodborne Illness