In September 1994, a complaint was registered at a
public health unit concerning a cheese
product. In addition, public health laboratories in Ontario
reported an increase in the number
of isolates of Salmonella berta from patients with
diarrhoeal illness. A clinical, environmental
and laboratory investigation was initiated to determine the
nature of this outbreak. Isolates of
Salmonella berta were compared using large fragment
genomic fingerprinting by pulsed-field gel
electrophoresis (PFGE). By late October, 82 clinical cases
had been identified including 35
confirmed, 44 suspected and 3 secondary. The investigation
linked illness to consumption of an
unpasteurized soft cheese product produced on a farm and sold
at farmers' markets. Subtyping
results of patient, cheese and chicken isolates were
indistinguishable, suggesting that the cheese
was contaminated by chicken carcasses during production.
The outbreak illustrates the
potential role of uninspected home-based food producers
and of cross-contamination in the
transmission of foodborne bacterial pathogens.