Questions and Answers
What type of environment is Aeromonas spp. widely distributed in?
Aeromonas spp. are recognized as enteric pathogens in the same manner as more common enteric pathogens.
False
What is the optimum growth temperature for the mesophilic group of Aeromonas spp.?
37 degC
The __________ group of Aeromonas spp. has an optimum growth temperature of 22 degC.
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Which of the following is a clinical manifestation associated with Aeromonas spp.?
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Which species is most frequently associated with gastrointestinal infections due to Aeromonas spp.?
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How many diarrheal presentations are observed with Aeromonas spp. infections?
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What is the most common presentation of wound infections caused by Aeromonas spp.?
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What biochemical test is important for differentiating aeromonads from enterics?
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Which Aeromonas species is strongly associated with aeromonad sepsis?
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Study Notes
Aeromonas spp. Overview
- Ubiquitous in freshwater, estuarine, and marine environments.
- Identified as oxidase-positive and glucose-fermenting bacteria.
- Seasonally prevalent in warmer months within the U.S.
- Clinical isolates predominantly from A.veronii with two biovars.
Classification
- Divided into mesophilic (optimum growth at 37°C) and psychrophilic (optimum growth at 22°C) groups.
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Mesophilic Group includes three complexes:
- A.hydrophila complex: A.hydrophila, A.bestiarum, A.salmonicida (motile strains).
- A.veronii complex: A.veronii biovar sobria, A.veronii biovar veronii, A.jandaei, A.trota, A.schubertii.
- A.caviae complex: A.caviae, A.media, A.eucrenophila.
- Psychrophilic Group: Primarily A.salmonicida, which is a fish pathogen but not known to infect humans.
Clinical Manifestations
Intestinal Manifestations
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Recognized as enteric pathogens, exhibiting virulence similar to certain E.coli subgroups.
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Five diarrheal presentations include:
- Acute, secretory diarrhea (with vomiting).
- Acute dysentery-like diarrhea (blood and mucus present).
- Chronic diarrhea lasting over 10 days.
- Cholera-like disease (rice water stools).
- Nebulous syndrome (traveler's diarrhea).
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Gastrointestinal infections: Most notable for A.caviae, especially in neonates and associated with inflammatory bowel disease.
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Other implicated species include A.hydrophila and A.veronii.
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Serious complications can result in hemolytic uremic syndrome (HUS) and kidney disease.
Extraintestinal Infections
- Septicemia and meningitis are common, with additional cases of wound infections.
- Implicated in osteomyelitis, pelvic abscess, keratitis, and endophthalmitis.
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Wound Infections:
- Associated with recent aquatic trauma, primarily affecting extremities.
- Common presentation is cellulitis.
- Notable isolates: A.hydrophila, A.veronii biovar sobria, and A.schubertii.
Culture and Colony Morphology
- Grows in most media used for routine and stool cultures.
- Characteristic colonies appear large, round, raised, opaque with smooth edges, and often have a mucoid surface.
- Notable for producing a strong odor, with pigmentation ranging from translucent to buff-colored.
- Hemolysis on sheep blood agar (SBA) can vary by species.
- Optimal isolation made on SBA without ampicillin; ampicillin may inhibit some A.caviae.
- Modified CIN II media enhances recovery of aeromonads, producing pink-centered colonies that ferment mannitol.
Biochemical Testing
- Critical for screening suspicious colonies on SBA.
- Oxidase Test: Positive, differentiating aeromonads from other enterics.
- Spot Indole Test: Indole-positive for the most clinically relevant species.
- String Test: Negative, distinguishing from Vibrio spp..
- O/129 Sensitivity: Aeromonas spp. are resistant.
- Demonstrated growth in sodium chloride as an identifying factor.
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Description
This quiz covers the characteristics of Aeromonas species, highlighting their environmental distribution, clinical significance, and seasonal patterns. Explore their classification, growth conditions, and the specific species isolated from various sources. Test your knowledge on this important group of bacteria in different environments.
