Introduction to Epidemiology

Salmonella
Most people associate salmonella infection (salmonellosis) with raw or undercooked poultry or meat, but it can be found on fruits and vegetables that are not cooked or washed properly as well. A food handler may also spread salmonella to foods if they do not properly wash their hands after using the bathroom. Etiologic Agent

The etiologic agent for Salmonella is enterobacteriaceae of the genus Salmonella, a gram-negative rod-shaped bacilli. Salmonellosis, the common salmonella infection, is caused by a variety of serotypes (most commonly S. enteritidis) and is transmitted from contaminated food such as poultry and eggs. The severest form of salmonella infections, “typhoid” (enteric fever), caused by Salmonella typhi, is rarely seen in the US, although it is one of the historical causes of widespread epidemics and still is in the third world countries. According to Kenneth Todar “all Enterobacteriaceae, the genus Salmonella has three kinds of major antigens with diagnostic or identifying applications: somatic, surface, and flagellar” (Todar, 2012). Host Factors

Salmonella Enteritidis causes little to no disease in its natural host, for example, poultry and is one of the most important causes of food borne outbreaks in humans. This means preventing this disease in the natural host would be very difficult. People that are of high risk are the young because their immune systems are immature as is their bacterial flora in their gastrointestinal tract, both of which are protective; and the aged because their immune systems are waning or declining. Other factors include persons

with decreased gastric acidity, altered gastrointestinal bacteria, immunosuppressed or immunocompromised, and persons taking opiate drugs in which the bowel motility is decreased. Environmental Factors

Salmonella bacteria love wet environments shielded from the sun. They survive between the pH’s of 4 to 8+, and can grow between 8 and 45 C. Salmonella are known to survive for long periods in soil and in water. Salmonella are facultative anaerobic bacteria that can survive under low oxygen tension such as in manure slurry pits. They have the remarkable ability to survive under adverse conditions.

Reference

Todar, K. P. (2012). Salmonella and Salmonellosis. Retrieved February 12, 2014, from Todar’s Online Textbook of Bacteriology: http://textbookofbacteriology.net/salmonella_2.html