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BBB - Plesiomonas shigelloides

Bad Bug Book:
Foodborne Pathogenic Microorganisms and Natural Toxins Handbook
Plesiomonas shigelloides

A new version of the Bad Bug Book was released in 2012, below is a previous version.


1. Name of the Organism:

Plesiomonas shigelloides

This is a Gram-negative, rod-shaped bacterium which has been isolated from freshwater, freshwater fish, and shellfish and from many types of animals including cattle, goats, swine, cats, dogs, monkeys, vultures, snakes, and toads.

Most human P. shigelloides infections are suspected to be waterborne. The organism may be present in unsanitary water which has been used as drinking water, recreational water, or water used to rinse foods that are consumed without cooking or heating. The ingested P. shigelloides organism does not always cause illness in the host animal but may reside temporarily as a transient, noninfectious member of the intestinal flora. It has been isolated from the stools of patients with diarrhea, but is also sometimes isolated from healthy individuals (0.2-3.2% of population).

It cannot yet be considered a definite cause of human disease, although its association with human diarrhea and the virulence factors it demonstrates make it a prime candidate.

2. Nature of Acute Disease:

Gastroenteritis is the disease with which P. shigelloides has been implicated.

3. Nature of Disease:

P. shigelloides gastroenteritis is usually a mild self-limiting disease with fever, chills, abdominal pain, nausea, diarrhea, or vomiting; symptoms may begin 20-24 hours after consumption of contaminated food or water; diarrhea is watery, non-mucoid, and non-bloody; in severe cases, diarrhea may be greenish-yellow, foamy, and blood tinged; duration of illness in healthy people may be 1-7 days.

The infectious dose is presumed to be quite high, at least greater than one million organisms.

4. Diagnosis of Human Illness:

The pathogenesis of P. shigelloides infection is not known. The organism is suspected of being toxigenic and invasive. Its significance as an enteric (intestinal) pathogen is presumed because of its predominant isolation from stools of patients with diarrhea. It is identified by common bacteriological analysis, serotyping, and antibiotic sensitivity testing.

5. Associated Foods:

Most P. shigelloides infections occur in the summer months and correlate with environmental contamination of freshwater (rivers, streams, ponds, etc.). The usual route of transmission of the organism in sporadic or epidemic cases is by ingestion of contaminated water or raw shellfish.

6. Relative Frequency of Disease:

Most P. shigelloides strains associated with human gastrointestinal disease have been from stools of diarrheic patients living in tropical and subtropical areas. Such infections are rarely reported in the U.S. or Europe because of the self-limiting nature of the disease.

7. Course of Disease and Complications:

P. shigelloides infection may cause diarrhea of 1-2 days duration in healthy adults. However, there may be high fever and chills and protracted dysenteric symptoms in infants and children under 15 years of age. Extra- intestinal complications (septicemia and death) may occur in people who are immunocompromised or seriously ill with cancer, blood disorders, or hepatobiliary disease.

8. Target Populations:

All people may be susceptible to infection. Infants, children and chronically ill people are more likely to experience protracted illness and complications.

9. Food Analysis:

P. shigelloides may be recovered from food and water by methods similar to those used for stool analysis. The keys to recovery in all cases are selective agars which enhance the survival and growth of these bacteria over the growth of the background microflora. Identification following recovery may be completed in 12-24 hours.

10. Selected Outbreaks:

Literature references can be found at the links below.

Gastrointestinal illness in healthy people caused by P. shigelloides infection may be so mild that they do not seek medical treatment. Its rate of occurrence in the U.S. is unknown. It may be included in the group of diarrheal diseases "of unknown etiology" which are treated with and respond to broad spectrum antibiotics.

Most cases reported in the United States involve individuals with preexisting health problems such as cancer, sickle cell anemia, immunoincompetence, the aged, and the very young, who develop complications.

For more information on recent outbreaks see the Morbidity and Mortality Weekly Reports from CDC.

11. Education and Background Resources:

Literature references can be found at the links below.

Loci index for genome Plesiomonas shigelloides

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.