(Yanko, 1988) Yesinia - streptococci - toxigenic E. coli - Leptospira spp - enterotoxigenic, enteropathogenic and

the genus Yersinia has grown to include eleven species (2,8,9,50), three of which are potentially pathogenic to humans:
Y. pestis, Y. pseudotuberculosis, and Y. enterocolitica
The association of human illness with consumption of Y. enterocolitica-contaminated food, animal wastes, and
unchlorinated water is well documented (4,5). Refrigerated foods are potential vehicles. because contamination is
possible at the manufacturing site (4) or in the home (5). This organism may survive and grow during refrigerated
Some strains of Y. enterocolitica and related species produce an in vitro heat-stable enterotoxin (ST). Virulent strains of
Yersinia invade mammalian cells such as HeLa cells in tissue culture (29). However, strains that have lost other virulent
properties retain HeLa invasiveness, because the invasive phenotype for mammalian cells is encoded by chromosomal
loci. Transfer of these genetic loci into E. coli confers the invasive phenotype to the E. coli host. all virulent Y.
enterocolitica isolates were shown to be tissue culture-invasive and to carry the ail gene.

The presence of a large number of S. aureus organisms in a food may indicate poor handling or sanitation; however, it
is not sufficient evidence to incriminate a food as the cause of food poisoning. The isolated S. aureus must be shown to
produce enterotoxins. Conversely, small staphylococcal populations at the time of testing may be remnants of large
populations that produced enterotoxins in sufficient quantity to cause food poisoning.  Processed foods may contain
relatively small numbers of debilitated viable cells, whose presence must be demonstrated by appropriate means.
Analysis of food for S. aureus may lead to legal action against the party or parties responsible for a contaminated food.
In all cases, the reactions of enterotoxigenic and nonenterotoxigenic strains varied by 12% or less. This research
indicates that none of these tests can be relied upon to differentiate toxic and nontoxic staphylococci.

Among the metabolites produced by Staphylococcus aureus, and other staphylo-coccal spp., enterotoxins (5,16,27)
present the greatest foodborne risk to the health of consumers. Staphylococcal enterotoxins are basic proteins
produced by certain Staphylococcus strains in a variety of environments, including food substrates. These
structurally-related, toxicologically similar proteins are produced primarily by Staphylococcus aureus, although S.
intermedius and S. hyicus also have been shown to be enterotoxaemia. When large numbers of enterotoxigenic
staphylococci grow in foods, they may elaborate enough toxin to cause food poisoning after the foods are ingested. The
most common symptoms of staphylococcal food poisoning, which usually begin 2-6 h after contaminated food is
consumed, are nausea, vomiting, acute prostration, and abdominal cramps.

The presence of small numbers of C. perfringens is not uncommon in raw meats, poultry, dehydrated soups and
sauces, raw vegetables, and spices. Because the spores of some strains are resistant to temperatures as high as
100°C for more than l h, their presence in foods may be unavoidable. Furthermore, the oxygen level may be sufficiently
reduced during cooking to permit growth of the clostridia. Spores that survive cooking may germinate and grow rapidly
in foods that are inadequately refrigerated after cooking.

The symptoms, which include intense abdominal cramps, gas, and diarrhea (nausea and vomiting are rare), have been
attributed to a protein enterotoxin produced during sporulation of the organism in the intestine. The enterotoxin can be
detected in sporulating cultures, and a method for this purpose is included. A high correlation has been established
between the ability of C. perfringens strains to produce enterotoxin and their ability to cause food poisoning. However, it
is difficult to obtain consistent sporulation with some strains. C. perfringens cells lose their viability when foods are
frozen or held under prolonged refrigeration unless special precautions are taken. Such losses may make it difficult to
establish C. perfringens as the specific cause of a food poisoning outbreak.