Vibrio, Aeromonas, Plesiomonas, and Campylobacter Flashcards
- found in water
- usually involved in epidemics
- causative agent of cholera
Vibrio species
rice water stool, large loss of electrolytes, dehydration and hypovolemic shock, diarrhea caused by toxin, fecal-oral transmission
cholera
rise in isolation of Vibrio
associated with water and water areas (seafood, coastal regions, tsunamis, etc.)
- facultative anaerobes, straight rods (can be curved on Gram stain)
- catalase and oxidase positive, reduce nitrate to nitrite (except V. metschnikovii)
- susceptible to Vibriostat disk (0/129), positive string test, halophilic
Vibrio
Vibriostat disk (0/129)
0/129 = 2,4-diamino-6,7-diisopropylpteridine
susceptibility differentiates Vibrio from Aeromonas
String test
emulsify 2-3 colonies in a drop of sodium desoxycholate
colonies can be picked up like a string
Vibrio Antigens
H antigen - all have it
O antigen - V. cholerae
O1 antigen
- O1, O139 are associated with epidemics (classic and El Tor)
- Non-O1 are milder, don’t produce cholera toxin
Cholera infection
- bacteria colonize small intestine and release toxin
- cholera toxin causes diarrhea (toxin has A and B subunits) which causes electrolyte and water loss
Treatment for cholera
IV fluids and electrolytes, antibiotics if significant infection
Vibrio parahaemolyticus
- cause of “Summer diarrhea of Japan”; associated with seafood; causes diarrhea and cramping
- heat-stable hemolysin (Kanagawa phenomenon); some strains are urease positive
Vibrio vulnificus
- atlantic, gulf and pacific coasts; from raw or undercooked seafood or wounds
- known as “lactose positive vibrio”; causes septicemia (serious infection)
Vibrio alginolyticus
mimics cholera; most frequently isolated; least pathogenic; mostly external (ears, wounds, burns)
Vibrio specimen collection
aspirates or tissue
Vibrio culturing
- greenish colonies on SBA
- BAP because of salt
- Mac (NLF except V. vulnificus)
- TCBS (thiosulfate, citrate, bile salts, sucrose)
TCBS (color change)
yellow (cholera, alginolycticus)
green (parahaemolyticus, vulnificus)
Vibrio susceptibility
susceptible to doxycycline and ciprofloxacin
- oxidase positive, glucose fermenting
- straight gram-negative rods
- mesophilic and psychophilic groups
- infection associated with contaminated water
Aeromonas
Mesophilic Aeromonas
motile
A. hydrophila complex
A. veronii complex
A. caviae complex
Psychrophilic Aeromonas
A. salmonicida; non-motile; grows best at 22-25C
Aeromonas (clinical infections)
- Gastroenteritits (contaminated water, Traveler’s diarrhea)
- Wound infection (A. hydrophila)
- Septicemia (A. veronii -liver disease, ICP most susceptible)
- osteomyelitis, pelvic abscesses, otitis, cystitis, etc.
Aeromonas identification
beta hemolytic oxidase positive indole positive string test negative resistant to Vibriostat disk grow well in 0% NaCl inositol negative
Aeromonas antimicrobial susceptibility
susceptible to trimethoprim, sulfamethoxazole (SMZ), aminoglycosides and quinolones
Plesiomonas
- gram-negative rods (part of enterobacteriaceae)
- similar to Shigella, but lower virulence
- soil and aquatic environments
Plesiomonas shigelloides
oxidase positive ferments glucose facultative anaerobe motile (polar flagella) susceptible to Vibriostat disk
Plesiomonas shigelloides (clinical infections)
- gastroenteritis (undercooked seafood - diarrhea, subacute or chronic)
- extraintestinal infections (found in snakes, lizards, newts - zoo keepers at risk)
- mostly self-limiting
Plesiomonas shigelloides (culturing)
- grow quickly on most media
- nonhemolytic colonies with raised center
- inositol brilliant green bile salts (IBB) - white or pink
Differentiating Plesiomonas shigelloides
- oxidase + rules out Enterobacteriaceae
- sensitivity to Vibriostat disk rules out Aeromonas
- no growth in high salt rules out Vibrio
- Inositol fermentation confirms Plesiomonas
- lysine and ornithine decarboxylase positive
- arginine dihydrolase positive
Campylobacter
- microaerophilic (5% O2)
- non-spore forming rods (seagull-wing shape)
- oxidase and catalase +
- darting motility
- nonfermentative
Campylobacter (clinical infections)
- transmission by contact with animals, contaminated food/water, person to person
- C. jejuni: #1 cause of diarrhea world-wide, self-limiting, associated with Guillain-Barre syndrome
- C. fetus: isolated from blood, causes abortion in animals
Helicobacter pylori
- colonizes 20-40% of adults; causes gastritis (type B)
- lives in mucus covering of stomach (doesn’t invade tissue)
- produces urease (urea –> ammonia) to neutralize stomach acid
- causes gastric carcinoma (stomach cancer)
Culturing Campylobacter and Helicobacter
- Campy blood agar plates (10% sheep blood)
- Skirrow media (lysed horse RBC’s)
- V media
- grow in capnophilic or microphilic environment
- organism exhibits corkscrew motility
Presumptive ID of Helicobacter
- Inoculate Christensen’s urea medium - (rapid color change in 2 hours)
- biopsy stomach specimen
- urea breath test
