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Food-Info.net> Topics > Food Safety > Bacteria > Overview of food-borne bacteria

Other enterobacteria :

Klebsiella, Citrobacter, Enterobacter species

General characteristics

These rod-shaped enteric (intestinal) bacteria have been suspected of causing acute and chronic gastrointestinal disease. The organisms may be recovered from natural environments such as forests and freshwater as well as from farm produce (vegetables) where they reside as normal microflora. They may be recovered from the stools of healthy individuals with no disease symptoms. The relative proportion of pathogenic to non-pathogenic strains is unknown.

Disease symptoms

Gastroenteritis is name of the disease occasionally and sporadically caused by these genera.

Acute gastroenteritis is characterized by two or more of the symptoms of vomiting, nausea, fever, chills, abdominal pain, and watery (dehydrating) diarrhoea occurring 12-24 hours after ingestion of contaminated food or water. Chronic diarrhoeal disease is characterized by dysenteric symptoms: foul-smelling, mucus-containing, diarrheic stool with flatulence and abdominal distention. The chronic disease may continue for months and require antibiotic treatment.

Infectious dose--unknown. Both the acute and chronic forms of the disease are suspected to result from the elaboration of enterotoxins. These organisms may become transiently virulent by gaining mobilizeable genetic elements from other pathogens. For example, pathogenic Citrobacter freundii which elaborated a toxin identical to E. coli heat-stable toxin was isolated from the stools of ill children

Diagnosis

Recovery and identification methods for these organisms from food, water or diarrhoeal specimens are based upon the efficacy of selective media and results of microbiological and biochemical assays. The ability to produce enterotoxin(s) may be determined by cell culture assay and animal bioassays, serological methods, or genetic probes.

Associated foods

These bacteria have been recovered from dairy products, raw shellfish, and fresh raw vegetables. The organisms occur in soils used for crop production and shellfish harvesting waters and, therefore, may pose a health hazard.

Prevention

Enterobacteria are heat-sensitive and will be killed by thorough heating (over 70 °C). Raw or undercooked foods and cross-contamination, when cooked material comes into contact with raw produce or contaminated materials (cutting boards), are the main causes of infection. Proper cooking and hygienic food handling thus can prevent enterobacterial infections to a large extend.

Risk populations

All people may be susceptible to pathogenic forms of these bacteria. Protracted illness is more commonly experienced by the very young.

Sources:

The bad bug book : http://www.cfsan.fda.gov/~mow/intro.html

 



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