Enteric Bacterial Infections 3: The Vibrios Flashcards
What are the three vibrios?
Vibrio cholerae, parahaemolyticus, vulnificus
Cellular characteristics of V. cholerae?
- Curved
- Motile
- Gram - rod
Two reservoirs of V. cholerae?
Humans and ocean
What cell wall antigen indicates pathogenicity in V. cholerae?
O cell wall antigen
What are the two V. cholerae groups that cause epidemic disease?
O1 and O139 groups
V. cholerae transmission?
Fecal-oral
What is a major barrier to V. cholerae infection?
Stomach acid
What makes a person susceptible to V. cholerae infection?
Gastrectomy, antacids, or coincident H. pylori infection
What allows the surviving V. cholerae to reach the small intestine brush border?
Secretion of mucinase and toxin-coregulated pilus
What are O1 and O139 markers for?
Infection with the CTX bacteriophage
Why is a high infectious dose of V. cholerae needed for infection?
Much of the organism is killed by gastric acid
Describe the choleratoxin
- A-B subunit structure
- B binds
- A causes percistent activation of adenylate cyclase resulting in loss of water and ions from attached cells
What is the Pavlovian Syx of V. cholerae infection?
Massive rice water diarrhea
What is the cause of morbidity and mortality from V. cholerae infection?
Dehydration and electrolyte imbalance
What is the typical scenario in which V. cholerae infection occurs?
Following travel
What is V. cholerae’s claim to fame in the diarrhea department?
Most watery diarrhea of any of the infectious gastroenteritis bugs
Typical Syx of V. cholerae infection?
- No fever
- No pain with diarrhea
- band hypokalemia from bicarb and K+ loss
- Hypoglycemia
Tx for V. cholerae infection?
Primarily rehydration
What is a simple test to determine the hydration status of a patient?
The longitudinal pinch test to assess skin turgor
Although not commonly performed, describe the culture technique for V. cholerae
- Use of bile salt agar
- Acid reaction on triple-sugar-iron agar
- Oxidase positive
- Sucrose (+)
What supportive measures are taken in the management of V. cholerae?
- Rehydrate and rebalance electrolytes - IV Lactated Ringer solution
- Oral Rehydration solution
- Tetracyclines if necessary
V. cholerae preventive methods
- Treat water, cook food
- Killed and live vaccine but not recommended for routine use in travelers
- Prophylactic tetracyclines
What is the typical scenario of a V. parahaemolyticus infection?
Typically gastroenteristis
Cellular characteristics of V. parahaemolyticus?
- Oxidase (+) Gram (-), Curved motile rod
- Halophile (lives in salty areas)
Which is more common? V. parahaemolyticus or V. vulnificus? More lethal?
V. p. is more common, V. h. is more lethal
Typical scenario of a V. vulnificus infection?
Lethal cellulitis
What is the leading cause of gastroenteritis in those whoe eat undercooked seafood?
V. parahaemolyticus
What is a very important point to make to a person with immunocompromise?
No more shellfish
What is the method to culture V. parahaemolyticus?
- Culture in 8% NaCl
- Culture from stool on thiosulfate-citrate-bile salts-sucrose media
Tx for parahaemolyticus?
Oral rehydration but if severe (high fever) doxycycline or quinolone
Characteristics that are similar b/w the V. cholerae and non-cholerae vibrios?
- Possibility of dehydration
- Self-limited (generally)
- Efficacy of doxycyline Tx
What is different b/w the V. cholerae and the non-cholerae vibrios?
- Likelihood of dehydration
- Likelihood of need for doxycycline
Cellular characteristics of V. vulnificus
- Oxidase (+)
- Gram (-)
- Halophile
What are the virulence factors of V. vulnificus?
- Hemolysin
- Protease exotoxin
- Siderophores - infection exacerbated by iron overload
What are the Pavlovian Hx characteristics?
Cellulitis with Hx of handling raw shellfish
Which bug has the highest case fatality rate for a foodborne illness?
V. vulnificus
Tx for V. vulnificus?
Early and often debridement; Ceftazidime + Doxycycline (or antipseudomonal penicillin)
What is similar in gastroenteritis and cellulitis caused by vibrios?
Exotoxin production and patient RFs for complications after infection