AEROMONADACEAE
Oxidase-positive Fermenters
Straight rods (not curved)
Originally written by Dr. Lillian Waldbeser, 2010; updated by Dr. Gregory Buck, March 2011
Disclaimer: You have permission to use handout if you are not a student in BIMS 4370 at Texas A&M Univ.-Corpus
Christi (TAMU-CC), but please acknowledge Drs. Lillian Waldbeser and Gregory Buck as the authors of this
document.
Family Aeromonadaceae (added in late 1990s and early 2000s)
• Of 17 proposed species, only eight isolated from clinical specimens
• Aeromonas hydrophila complex
• A. salmonicida a fish pathogen
• Aeromonas veronii complex
• Aeromonas trota
• Aeromonas caviae complex
• Several members of A. salmonicida are psychrophilic
• Remaining members of Aeromonas are mesophiles
GENUS: Aeromonas
- Ubiquitous
- Found in estuaries and marine environment
- Infect cold and warm blood animals
- Infections:
- Gastroenteritis:
- From eating raw oyster/clam
- From untreated well water
- Acute secretory diarrhea or
Acute dysenteric diarrhea with blood + leukocytes + mucus
- Chronic diarrhea, lasts >10 days
- Choleric type that includeds “rice-water” stools.
- Traveler’s diarrhea
- Self limiting except in pediatric and geriatric cases
- GI infections
• A. caviae —especially in neonates and pediatric populations
• A. hydrophila
• A. veronii biovar sobria, biovar veronii
• Cholera-like disease
• A. veronii biovar sobria
- Wound infections:
- From traumatic aquatic exposure
- Most common: cellulitis
- Most isolates: Aeromonas hydrophila, A. veronii biovar sobria,
A. schubertii (especially aquatic wounds and bloodstream infections
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- Septicemia in:
- Immunocompromised
- Liver disease
- Hematologic malignancy:
- leukemia, lymphoma, myeloma
- Leech therapy:
- Aeromonas hydrohila inhabits gut of leeches
- Hemolytic uremic infection
• A. hydrophila
• A. veronii biovar sobria
Laboratory Diagnosis
Bailey & Scott’s Diagnostic Microbiology
- Gram-negative, straight (not curved) rods
- Growth range: 00C - 450C
- Large raised translucent to white opaque colonies
- Most species are -hemolytic on BAP
- Strong odor
- Oxidase: +ve (therefore not Enterobacteriaceae)
- Most ferment lactose (pink on MAC)
- Ferments glucose
- Ferments glucose: differentiates it from Pseudomonas
- Most are motile
- Resistant to Vibrio static agent O/129
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- Grows on Cefsulodin-irgasin-novobiocin (CIN) plates
- Like vibrios, clinical specimens can be enriched in alkaline peptone water
- Spot indole test (+ve), oxidase, inability to grow in 6% NaCl
Textbook of Diagnostic Microbiology by Mahon & Manuselis
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Treatment
- For wound and systemic infections
- Third generation cephalosporin, aminoglycosides, & quinolones
- Resistant to: penicillin, ampicillin, carbenicillin, cephalothin
PLESIOMONAS
Only 1 species: Plesiomonas shigelloides
- Ancestry closer to Enterobacteriaceae (Proteus) than to Vibrio
- Soil / estuarine water
- In warm & cold blood animals, including shellfish
- Plesiomonas often seen in contact with reptiles and amphibians
- Causes Gastroenteritis:
- From eating uncooked oysters/shrimp/contaminated water
- 3 forms of gastroenteritis:
1. Watery diarrhea with no blood or mucus
2. Subacute or chronic disease; lasts 14 days to 2-3 months
in immunocompromised patients
3. Invasive dysenteric form - resembles colitis
- Other symptoms: Fever, vomiting, abdominal pain
- Self limited
- Laboratory Diagnosis
- Morphology: Straight (not curved) gram-neg rods
singly/ pairs/ short chains/ filamentous
- Colonies: Shiny, opaque, non-hemolytic on BAP
- Vibrio-like: - Facultative anaerobe
- Oxidase: +ve
- Ferments glucose
- Motile
- Sensitive to vibriostatic agent O/129
(differentiate it from Aeromonas)
- Gelatin liquefaction: -ve
(differentiate it from Vibrio and Aeromonas)
- Plesiomonas gastroenteritis presents with blood and WBCs in stool
(not true for Aeromonas)
- Treatment
- Quinolones
- Used only in acute/chronic cases or neonates
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