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U.S.
Food & Drug Administration Center for Food Safety & Applied Nutrition Foodborne Pathogenic Microorganisms and Natural Toxins Handbook |
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Miscellaneous enterics
| 1. Name of the Organism:
Miscellaneous enterics, Gram-negative genera including: Klebsiella, Enterobacter, Proteus, Citrobacter, Aerobacter, Providencia, Serratia |
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 nonpathogenic strains is unknown. |
| 2. Nature of Acute Disease: | Gastroenteritis is name of the disease occasionally and sporadically caused by these genera. |
| 3. Nature of Disease: | Acute gastroenteritis is characterized
by two or more of the symptoms of vomiting, nausea,
fever, chills, abdominal pain, and watery (dehydrating)
diarrhea occurring 12-24 hours after ingestion of
contaminated food or water. Chronic diarrheal 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. |
| 4. Diagnosis of Human Illness: | Recovery and identification methods for these organisms from food, water or diarrheal 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. |
| 5. 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. |
| 6. Relative Frequency of Disease: | Acute gastrointestinal illness may occur more frequently in undeveloped areas of the world. The chronic illness is common in malnourished children living in unsanitary conditions in tropical countries. |
| 7. Course of Disease and Complications: | Healthy individuals recover quickly and without treatment from the acute form of gastrointestinal disease. Malnourished children (1-4 years) and infants who endure chronic diarrhea soon develop structural and functional abnormalities of their intestinal tracts resulting in loss of ability to absorb nutrients. Death is not uncommon in these children and results indirectly from the chronic toxigenic effects which produce the malabsorption and malnutrition. |
| 8. Target Populations: | All people may be susceptible to pathogenic forms of these bacteria. Protracted illness is more commonly experienced by the very young. |
| 9. Food Analysis: | These strains are recovered by standard selective and differential isolation procedures for enteric bacteria. Biochemical and in vitro assays may be used to determine species and pathogenic potential. Not being usually thought of as human pathogens, they may easily be overlooked by the clinical microbiology laboratory. |
| 10. Selected Outbreaks: | Literature references can be found at the links below. |
| Intestinal infections with these species in the U.S. have usually taken the form of sporadic cases of somewhat doubtful etiology. | |
| MMWR 32(41):1983 | Citrobacter freundii was suspected by CDC of causing an outbreak of diarrheal disease in Washington, DC. Imported Camembert cheese was incriminated. |
| MMWR 33(2):1984 | Cases of similar clinical illness have subsequently been identified in four states (Colorado, Georgia, Illinois, and Wisconsin) associated with eating the same brand of semi-soft cheese (either Brie or Camembert). The lots implicated in these states included at least one lot produced approximately 40 days after the cheese that caused the District of Columbia cases. |
| Morbidity and Mortality Weekly Reports | For more information on recent outbreaks see the CDC. |
| 11. Education and Background Resources: | Literature references can be found at the links below. |
| Loci index
for genome Klebsiella
spp. Enterobacter spp. Proteus spp. Citrobacter spp. Providencia spp. Serratia spp. |
Available from the GenBank Taxonomy database, which contains the names of all organisms that are represented in the genetic databases with at least one nucleotide or protein sequence. |
| 12. Molecular Structural Data: | None currently available. |
mow@cfsan.fda.gov
January 1992 with periodic updates
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