Plesiomonas shigelloides
- Plesiomonas is derived from the Greek word where it means “neighbor”.
- It indicates Plesiomonas has a close association with
- It is included in the family Enterobacteriaceae.
- P. shigelloides is the only species in the genus.
Classification of Plesiomonas shigelloides:
- Kingdom: Bacteria
- Phylum: Proteobacteria
- Class: Gammaproteobacteria
- Order: Enterobacteriales
- Family: Enterobacteriaceae
- Genus: Plesiomonas
- Species: shigelloides
Clinical Significance of Plesiomonas shigelloides:
- Plesiomonas shigelloides is present in surface waters and soil.
- Different cold-blooded animals like frogs, snakes, turtles, lizards are infected by
- By the ingestion of contaminated food, humans become infected with it.
- Despite its less frequent recovery from human feces as compared to Aeromonas, Plesiomonas-induced gastroenteritis has been reported in children and adults.
- In humans, Plesiomonas-related gastroenteritis is manifested as mild watery diarrhea.
- In this condition, stools are free of blood and mucin.
- In the immunosuppressed patients or persons having GI malignancies, severe colitis or a cholera-like illness may be seen.
- The prevalence of this infection is more during the warm summer months and in the subtropical and tropical regions of the world.
- It produces enteropathogenic enterotoxin.
- It has caused illness after uncooked shellfish consumption.
- It is also a cause of travelers’ diarrhea.
- Extraintestinal infections have also been reported such as:
- Septicemia
- neonatal meningitis
- cellulitis
- septic arthritis
- acute cholecystitis
- Other reported cases are:
- Postsplenectomy infection
- Plesiomonas shigelloides-associated persistent dysentery
- pseudomembranous colitis
Laboratory diagnosis of Plesiomonas shigelloides:
- P. shigelloides is a straight-to-rounded, short, Gram-negative bacteria.
- Motile
- Have lophotrichous flagella
- grows well on sheep blood agar and most enteric media.
- nonhemolytic on sheep blood agar
- Grows at the incubation of 24 hours at 30°C- 35°C.
- optimum growth temperature is 30°C
- Colony characteristics of Plesiomonas shigelloides:
- average 1.5 mm in diameter
- gray
- shiny
- smooth
- opaque
- slightly raised in the center.
- Culture media for shigelloides:
- MacConkey Agar
- Deoxycholate Agar
- Hektoen agar
- xylose lysine deoxycholate Agar
- Glucose fermentation takes place and appears as yellow in:
- Kligler’s iron agar
- triple sugar iron agar
- Non-lactose fermenter in MacConkey agar and make confusion with Shigella spp
- oxidase-positive
- indole positive.
- decarboxylates arginine, lysine, and ornithine
- does not produce DNase or extracellular proteases
- ferments inositol but not mannitol
Biochemical Characteristics of Plesiomonas shigelloides:
| Hemolysis on sheep blood | No haemolysis |
| Oxidase | Positive |
| Motility | Positive |
| DNase | negative |
| Indole | Positive |
| Voges-Proskauer | negative |
| Decarboxylase test: | |
| Lysine | positive |
| Ornithine | positive |
| Arginine | positive |
| Esculin test | negative |
| Fermentation: | |
| Gas from Glucose fermentation | negative |
| L-Arabinose | negative |
| Sucrose | negative |
| Mannitol | negative |
| Inositol | positive |
Antibiotic Susceptibility of Plesiomonas shigelloides :
- Resistant to penicillin, ampicillin, carbenicillin, and other β-lactamase susceptible penicillins.
- susceptible to the aminoglycosides, chloramphenicol, tetracycline, trimethoprim-sulfamethoxazole and the quinolones, ciprofloxacin, and norfloxacin.