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Food Microbiology
Staphylococcus aureus is a common cause of bacterial foodborne
disease worldwide. Symptoms include vomiting and diarrhea that occur shortly
after ingestion of S. aureus-contaminated food. The symptoms arise from
ingestion of preformed enterotoxin, which accounts for the short incubation
time. Staphylococcal enterotoxins are superantigens and, as such, have adverse
effects on the immune system. The enterotoxin genes are accessory genetic
elements in S. aureus, meaning that not all strains of this organism are
enterotoxin-producing. The enterotoxin genes are found on prophage, plasmids,
and pathogenicity islands in different strains of S. aureus.
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Infections are commonly acquired by animal to
human transmission though consumption of undercooked food products derived from
livestock or domestic fowl.
Shigella species are members of the family Enterobacteriaceae and
are Gram negative, non-motile
rods. Symptoms include mild to
severe diarrhea with or without
blood, fever, tenesmus, and abdominal
pain. Further complications of the disease may be seizures, toxic megacolon,
reactive arthritis and hemolytic
uremic syndrome. Transmission of the pathogen is by the fecal-oral route,
commonly through food and water. The infectious dose ranges from 10-100
organisms.
E. coli was considered a commensal of human and animal intestinal tracts with low virulence potential. It is now known that many strains of E. coli act as pathogens inducing serious gastrointestinal diseases and even death in humans.
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