Shigella association with Foods
The principal foods involved in Shigella outbreaks were a variety of salads and seafood which became contaminated during handling by infected workers.
This was frequently coupled with improper refrigeration. After the initial infection from contaminated food, the disease readily spreads from person to person by the fecal-oral route of transmission.
Shigellas usually are considered to be relatively fragile; i.e., they do not survive well outside the host. Like most other members of the family Enterobacteriaceae, they are readily killed by most heat treatments employed in the processing and preparation of foods, and do not survive well at pH below 4.5.
However, studies on the survival of Shigella suggest that under certain selected conditions, they can survive for extended periods in foods.
For example, Shigella sonnei and Shigella flexneri have been reported to survive at 25 degree C (77 degree F) in flour and in pasteurized whole milk for more than 170 days; in eggs, clams, and shrimp for more than 50 days; and in eggs whites for more than 20 days.
At lower temperatures such as -20 degree and 0.5 degree C survival for longer periods has been reported.
Laboratory data suggest that Shigella may survive for extended periods on foods and may grow under selected conditions. However, in practice, shigellae are rarely isolated from processed products.
Manufacturers do not routinely test their products, raw materials or processing environment for Shigella, and there is no evidence to suggest that routine testing is warranted.
Most outbreaks result from contamination of raw or previously cooked foods during preparations in the homes or in foodservice establishments. Generally, the source of contamination can be traced to a carrier whose personal hygiene is poor.
Shigella association with Foods
