Salmonellosis Update

Salmonellosis is fairly common. Many species and types of salmonellae are known, over 2300, with all considered pathogenic for humans; some strains are more virulent than others. They can grow between 41 F and 114 F, with the organism being able to double its growth every 25 minutes at about human body temperature, 95 F- 98.6 F. The organism can survive freezing.

Salmonella are found in the intestinal tract of animals and humans, with cycles of infection between animals, humans and the environment. Animal food products- meats, poultry, eggs and items made with them- may contain the bacteria; any contaminated foods rich in protein and carbohydrates are particularly vulnerable. Sometimes humans (especially as carriers) can be directly or indirectly a source of contamination, with poor handwashing (personal hygiene) playing a vital role in transmission from a human.

Foods that have been implicated with salmonellosis include poultry and poultry salads, meat and meat products, dairy products, egg products, and other protein foods. The prevalence of the bacteria in foods is variable. Studies have shown that about half of chicken carcasses are contaminated with salmonellae, with pig carcasses having lesser contamination, and beef and lamb carcasses having the least contamination. Vegetables, fruits, salads, and cereals can be contaminated with salmonellae but at much lower levels than meats. Most vulnerable foods are those handled extensively, left unrefrigerated for periods of time, and then lightly cooked or served without further cooking.

Salmonella problems from shell eggs emerged during the 1980's. In 1990 FDA again declared shell eggs a potentially hazardous food, making them subject to time/temperature controls. Studies have indicated that most outbreaks that occurred in this time frame appear to be related to pooling (commingling) of eggs, temperature abuse, and incomplete cooking (egg mixture runny).

Prevention of salmonellosis is based on four principles:

1. Cooking foods thoroughly and serving them HOT (above 140 F) and not just WARM.

2. Preventing recontamination (cross-contamination) by using sanitary practices of food protection and sanitation (cleanliness, especially of the hands and food contact surfaces, and proper use of equipment, utensils [are knives cleaned and sanitized between uses?], and dishware).

3. Prompt cooling (freezing) of foods after preparation (if prepared ahead) to retard multiplication of bacteria, especially by storing in shallow pans (food not over 2 inches in depth) or in smaller quantities or portions. Do not hold foods at room temperature.

4. Complete reheating (to at least 165 F) of stored refrigerated foods in or on proper heating units, not by using warming (holding) units.

Remember, foods contaminated with salmonella bacteria do not usually appear to be "bad" (spoiled), so that changes in odor and taste are not apparent.

Karen Penner, Ph.D.
Extension Specialist, Food Science

7/94 File: FOOD SAFETY/Microorganisms

K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus, Manhattan.