Vibrio species (non-cholera)
Vibrio species (non-cholera)
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- Aerobic, Gram-negative, comma-shaped rod (1-3 x 0.5-0.8µm, Fig).
- Grows best in warm, low salinity marine water. Coastal waters/estuaries are ideal. As marine environments warm, these organisms have spread to new areas and are increasingly important causes of human infections.
- Rates of infections in the U.S. have tripled over the past two decades. Estimated to cause approximately 80,000 cases and 100 death each year (most are not laboratory confirmed).
- Most important non-cholera species are V. parahaemolyticus (62% of cases), V. alginolyticus (13%) and V. vulnificus (10% of cases and ~50% mortality).
- Vibrio parahaemolyticus:
- Most common non-cholera vibrio to cause infections.
- Typical presentations:
- GI disease: diarrhea, associated with consumption of contaminated fish/seafood.
- Can also cause skin infections from direct exposure of open wounds to sea water.
- Most environmental strains are non-pathogenic.
- Pathogenic strains carry a hemolysin toxin: thermostable direct hemolysin (TDH) and/or TDH related hemolysin (TRH). Strains with TDH cause hhemolysis on special blood agar plates (kanagawa reaction).
- Vibrio vulnificus: Less common but more lethal. ~95% of seafood associated mortality is related to this organism.
- Part of the normal microbial ecology of estuarine water and mollusks (e.g. in Chesapeake Bay, areas of coast off of Gulf of Mexico).
- Infection can be acquired via ingestion of contaminated seafood or direct inoculation of water onto skin.
- There are 3 recognized biotypes, of which biotype 1 is most important cause of human infection.
- Important toxins are collagenases, metalloproteinases and lipases/phospholipases that lead to tissue destruction, and endotoxin which leads to hypotension and organ failure
- Vibrio alginolyticus:
- Emerging pathogen typically impacting people in coastal communities
- Non-foodborne infections predominate (~86%) and typically affect lower extremity skin or external ears after swimming in warm coastal waters.
- Other occasional Vibrio species causing human infection: V. fluvialis, V. fumissii, V. hollisae, V. damsela, V. cincinnatiensis.
- Cholera is caused by V. cholerae (see that module for details)
- Obtain from suspected source, e.g., blood (sepsis), wound (wound infection), stool (gastroenteritis).
- Organisms grow well on routine media and in blood cultures.
- Notify micro lab if suspected as cause of gastroenteritis to use special selective media for stool specimen such as thiosulfate citrate bile salt sucrose (TCBS).
- Some labs in endemic areas routinely use this media as part of stool culture protocol during summertime/warmer weather.
- Diagnosis of GI illness due to V. parahaemolyticus is increasingly made via non-culture based (e.g. molecular) assays as part of multiplex panel.
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