Staphylococcus aureus, or particula

Staphylococcus aureus, or particularly the enterotoxin it can produce, has
caused problems in canned foods. It is a gram-positive coccus of the
Micrococcaceae family. Illness results from the ingestion of foods containing
an enterotoxin produced by certain strains of this organism, which is
commonly found in the nasal passages and skin of humans and animals.
While the foods most frequently implicated in outbreaks are ready to eat
(e.g., cooked meats, cream pastries, etc.), the enterotoxin can remain
biologically active after cooking and even after the thermal processing used
in canning of low-acid foods (Dangerfield, 1973). A case in point isthe 1989
outbreaks of S. aureus intoxication in the United States due to the
consumption of canned mushrooms in which, in some instances, the toxin
was believed to have been produced in the mushrooms prior to their being
thermally processed (Bennett, 1992). Selective media permit the isolation,
identification, and enumeration of the microorganism and provide a
quantitative evaluation of any problem. There are now a number of rapid
methods for the direct identification of the presence of the enterotoxin in
foods.
The organism is found abundantly in nature, with certain strains being
saprophytic to both humans and animals, while others are enterotoxigenic.
As it is estimated that 25-50% of the human population are carriers of S.
aureus, food handlers must be considered as a significant source of
contamination by this organism. It has also been shown that contamination
of carcasses and processed animal products also comes from the equipment
(e.g., knives, etc.) used in slaughterhouses. The contamination of poultry
carcasses by the fingers of the pluckers is a good example and, notwithstanding
the potential for human contamination, it should be kept in mind
that in modern large-scale poultry slaughterhouses it is the mechanical
pluckers, that constitute a critical control point for the supply and
dissemination of S. aureus to the carcasses.
Phytopathogens attack fruits and vegetables, reducing their organoleptic
and nutritional quality, and causing the appearance of mechanical quality
defects (Lelliot and Stead, 1987). For example, the tomato can be attacked
by eight types of parasites that belong to the species Pseudomonas,
Xanthomonas, and Clavibacter (Smith et al., 1988), and green beans by
Corynebacterium , Pseudomonas, and Xanothomonas. The lesions caused by
thes e bacteria continue to expand after the harvest, but adjacent healthy
products are not affected as long as there is no entrainment by way of water
or infectious inoculum (Bartz and Eckert, 1987). With adequate
precautions, it is only a serious risk because of the economic loss to
vegetable products stored and sold fresh.
Agents that cause soft rot deserve special mention. In order of
decreasing importance, these are the species Erwinia , Pseudomonas, and
Clostridium , and they have been intensively studied in leafy products,
potatos, carrots, tomatos, celery, and cauliflower (Denis and Picoche, 1986).