''Plesiomonas shigelloides'' is a species of bacteria and the only member of its genus. It is a

Gram-negative Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wa ...

, rod-shaped

bacterium Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were amon ...

which has been isolated from freshwater, freshwater fish, shellfish, cattle, goats, swine, cats, dogs, monkeys, vultures, snakes, toads and humans. It is considered a

fecal coliform A fecal coliform (British: faecal coliform) is a facultatively anaerobic, rod-shaped, gram-negative, non-sporulating bacterium. Coliform bacteria generally originate in the intestines of warm-blooded animals. Fecal coliforms are capable of growth ...

. ''P. shigelloides'' is a global distributed species, found globally outside of the polar ice caps. ''P. shigelloides'' has been associated with the diarrheal disease state in humans, but has been identified in healthy humans as well. It can enter the body either through contact with water contaminated by fecal matter or through seafood originating from a contaminated source.

Classification

''P. shigelloides'' was originally considered part of the family ''Vibrionaceae'', but is generally accepted to be part of ''Enterobacteriaceae'' due to the similarity of its 5S

rRNA Ribosomal ribonucleic acid (rRNA) is a type of non-coding RNA which is the primary component of ribosomes, essential to all cells. rRNA is a ribozyme which carries out protein synthesis in ribosomes. Ribosomal RNA is transcribed from ribosoma ...

sequence to other members of ''Enterobacteriaceae'.'' The rRNA sequence of ''P. shigelloides'' has been found to be most similar to ''

Proteus mirabilis ''Proteus mirabilis'' is a Gram-negative, facultatively anaerobic, rod-shaped bacterium. It shows swarming motility and urease activity. ''P. mirabilis'' causes 90% of all ''Proteus'' infections in humans. It is widely distributed in soil and ...

,'' and as a result it is now considered part of the tribe ''Proteeae'' within the family ''Enterobacteriaceae''. ''P. shigelloides'' is the only known member of its genus.

Ecology

Growth

''P. shigelloides'' is incapable of surviving in saltwater environments where the concentration of salt is greater than 4% and has been found to tolerate pH ranges between 4.5 and 9. It grows optimally between 35°C and 39°C, and has been found to survive in the temperature range of 8°C to 45°C. The effects of pH, salinity, temperature, turbidity, and conductivity on concentrations of ''P. shigelloides'' in freshwater conditions is not currently understood.

Identification

Some ''Plesiomonas'' strains share antigens with ''

Shigella sonnei ''Shigella sonnei'' is a species of ''Shigella''. Together with ''Shigella flexneri'', it is responsible for 90% of shigellosis cases. ''Shigella sonnei'' is named for the Danish bacteriologist Carl Olaf Sonne. It is a Gram-negative, rod-shaped ...

'', and cross-reactions with ''Shigella'' antisera may occur. ''Plesiomonas'' can be distinguished from ''Shigella'' in diarrheal stools by an

oxidase test The oxidase test is used to determine if an organism possesses the cytochrome c oxidase enzyme. The test is used as an aid for the differentiation of ''Neisseria'', ''Moraxella'', ''Campylobacter'' and ''Pasteurella'' species (oxidase positive). It ...

: ''Plesiomonas'' is oxidase positive and ''Shigella'' is oxidase negative. ''Plesiomonas'' is easily differentiated from ''Aeromonas sp.'' and other oxidase-positive organisms by standard biochemical tests.

Pathogenicity

Human infection

''P. shigelloides'' has been isolated from a wide variety of human clinical specimens including both intestinal (usually feces or rectal swabs) and extra-intestinal. It has been isolated from the feces of humans, both with and without diarrhea, and/or vomiting ( gastroenteritis). Although reports have found a link between ''P. shigelloides'' and

diarrhea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin w ...

or gastroenteritis, research has not yet determined whether this bacteria is always responsible for these conditions.

Infection of other animals

Although ''P. shigelloides'' is primarily associated with the diarrheal disease state in humans, certain animals including cats and dogs have been found to frequently carry the bacterium while in a healthy state. Freshwater fish can often be infected with ''P. shigelloides'' which can be lethal depending on the concentration of the bacterium in their bodies.

References

External links

Type strain of ''Plesiomonas shigelloides'' at Bac''Dive'' - the Bacterial Diversity Metadatabase
Bacteria described in 1954 {{gammaproteobacteria-stub