51. Vibrio and Aeromonas

Question 1

V. cholerae general characteristics?

Answer 1

• GNR
• Facultative anerobe
• motile
• growth stimulated by Na+
• serological differentiation based on O (LPS) antigen

Question 2

V. cholerae epidemiology?

Answer 2

Common inhabitants of aquatic env’t

• O1 and O139 involved in epidemics
• only diarrheal disease capable for pandemic spread
• fecal-oral transmission
• increased severity in people w/hypochlorhydria
• large inoculum required for infection

Question 3

V. cholerae pathogenesis and virulence factors?

Answer 3

• V.cholerae non-O1 or O139 are common inhabitants of brackish water, do not produce CT or contain pathogenicity island, usu no disease, but occas. diarrhea/non-GI disease
• V.cholerae colonizes proximal small intestine and secretes CT.
• CT increases cAMP levels in intestinal epithelial cells, leading to increased secretion of chloride ions and decreased absorption of sodium ions
• water follows gradient of ions
• ToxR is a global regulator of virulence factors in V.cholerae: enables vibrios to respond to changes in the env’t and express virulence factors accordingly

Cholera Toxin (CT) only associated with O1 and O139 serogroups. Possess a pathogenicity island encoding intestinal colonization factors

• A-B subunit toxin (5B:1A), B binds holotoxin to GM1 ganglioside receptors on enterocyte (phage-encoded)
• A enters cell where it ADP-ribosylates GTP binding protein (Gsa) to cause AC to be permanently turned on
• increase in cAMP: more secretion of Cl- and less absorption of Na+ (CFTR – Cl- secretion from ctypt cells and inhibition of Na+/Cl- absorption of villus cells)

TCP = toxin-coregulated pilus is a type IV pilus whose expression is co-regulated w/CT
- essential for intestional colonization

Question 4

V. cholerae disease and dx?

Answer 4

• dehydrating diarrheal illness w/loss of fluids and electrolytes (secretory diarrhea)
• diarrhea, vomiting, leg cramps
• hypovolemic shock
• sunken eyes
• many infections are sub-clinical and spread disease
• rice water stools (fluid loss may exceed >1L/hr)
• poor skin turgor
• rapid onset

Question 5

V. cholerae tx/prevention?

Answer 5

• replace lost water and salts PO or IV (severe)
• Abx (azithromycin, doxycycline, FQ for adults; azithromycin for kids) can help but not essential
• prevent w/adequately cooked seafood and adequate sanitation
• Vaccine (oral whole killed vibrios): purified B subunit vaccine (immunogenic and non-toxic) and promoter but not full A subunit (the toxin)

Question 6

V. parahaemolyticus general characteristics?

Answer 6

GNR

• facultative anaerobe
• motile
• growth stim by Na+

Question 7

V. parahaemolyticus epidemiology?

Answer 7

• leading bacterial cause of seafood-assoc gastroenteritis
• outbreaks w/coastal states w/crabs, oysters, shrimp
• short generation time (9 min)
• peak in summer

Question 8

V. parahaemolyticus pathogenesis/virulence factors?

Answer 8

• enterotoxin (TDH) – 95% of stains from disease have this, only

Question 9

V. parahaemolyticus disease and tx?

Answer 9

• gastroenteritis
• watery, self-limited diarrhea w/cramps, nausea, vomiting, sometimes bloody diarrhea (rare)
• wound infections after exposure to warm seawater: cellulitis (vesicles or bullae followed by necrosis)
• can lead to bacteremia and death (esp w/liver disease)

tx: REHYDRATION

Question 10

V. vulnificus general characteristics?

Answer 10

• GNR
• facultative anaerobe
• motile
• growth sim by Na+

Question 11

V. vulnificus epi?

Answer 11

• eating raw seafood
• those w/pre-existing hepatic or chronic disease (AIDS, cirrhosis, malignancy, hemochromatosis, immunosupp Rx)
• 90% males

Question 12

V.vulnificus pathogenesis/virulence factors?

Answer 12

• polysaccharide capsule ressits phagocytosis and serum bactericidal action; endotoxin  shock
• degradative enzymes

Question 13

V.vulnificus disease and tx?

Answer 13

• primary wound infections re: healthy people
• primary sepsis: chills, fever, prostration, and hypotension
• secondary skin lesions on extremities – erythematous or ecchymotic areas (vesicles or bullae): necrotic ulcers

tx:

• prevention: no raw seafood for those w/pre-disposing conditions
• debridement, amputation, tetracycline plus ciprofloxacin or cefotaxime

Question 14

Aeromonas (A.hydrophila) general characteristics? disease? Tx?

Answer 14

• Water, soil reservoir
• healthy and compromised pts
• high asymptomatic carriage rate

disease:

• wound infections, cellulitis re: water and soil exposure, leeches
• acute diarrheal disease
• bacteremia assoc w/malignancy, hepatic, biliary, or pancreatic disease

tx:

• S/ST: TMP-SMX, FQ, aminoglycosides but resistant to B-lactams
• diarrhea: rehydration