Vibrio, Aeromonas, Plesiomonas, and Campylobacter

Question 1

• found in water
• usually involved in epidemics
• causative agent of cholera

Answer 1

Vibrio species

Question 2

rice water stool, large loss of electrolytes, dehydration and hypovolemic shock, diarrhea caused by toxin, fecal-oral transmission

Answer 2

cholera

Question 3

rise in isolation of Vibrio

Answer 3

associated with water and water areas (seafood, coastal regions, tsunamis, etc.)

Question 4

• 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

Answer 4

Vibrio

Question 5

Vibriostat disk (0/129)

Answer 5

0/129 = 2,4-diamino-6,7-diisopropylpteridine

susceptibility differentiates Vibrio from Aeromonas

Question 6

String test

Answer 6

emulsify 2-3 colonies in a drop of sodium desoxycholate

colonies can be picked up like a string

Question 7

Vibrio Antigens

Answer 7

H antigen - all have it

O antigen - V. cholerae

Question 8

O1 antigen

Answer 8

• O1, O139 are associated with epidemics (classic and El Tor)
• Non-O1 are milder, don’t produce cholera toxin

Question 9

Cholera infection

Answer 9

• bacteria colonize small intestine and release toxin

- cholera toxin causes diarrhea (toxin has A and B subunits) which causes electrolyte and water loss

Question 10

Treatment for cholera

Answer 10

IV fluids and electrolytes, antibiotics if significant infection

Question 11

Vibrio parahaemolyticus

Answer 11

• cause of “Summer diarrhea of Japan”; associated with seafood; causes diarrhea and cramping
• heat-stable hemolysin (Kanagawa phenomenon); some strains are urease positive

Question 12

Vibrio vulnificus

Answer 12

• atlantic, gulf and pacific coasts; from raw or undercooked seafood or wounds
• known as “lactose positive vibrio”; causes septicemia (serious infection)

Question 13

Vibrio alginolyticus

Answer 13

mimics cholera; most frequently isolated; least pathogenic; mostly external (ears, wounds, burns)

Question 14

Vibrio specimen collection

Answer 14

aspirates or tissue

Question 15

Vibrio culturing

Answer 15

• greenish colonies on SBA
• BAP because of salt
• Mac (NLF except V. vulnificus)
• TCBS (thiosulfate, citrate, bile salts, sucrose)

Question 16

TCBS (color change)

Answer 16

yellow (cholera, alginolycticus)

green (parahaemolyticus, vulnificus)

Question 17

Vibrio susceptibility

Answer 17

susceptible to doxycycline and ciprofloxacin

Question 18

• oxidase positive, glucose fermenting
• straight gram-negative rods
• mesophilic and psychophilic groups
• infection associated with contaminated water

Answer 18

Aeromonas

Question 19

Mesophilic Aeromonas

Answer 19

motile
A. hydrophila complex
A. veronii complex
A. caviae complex

Question 20

Psychrophilic Aeromonas

Answer 20

A. salmonicida; non-motile; grows best at 22-25C

Question 21

Aeromonas (clinical infections)

Answer 21

• Gastroenteritits (contaminated water, Traveler’s diarrhea)
• Wound infection (A. hydrophila)
• Septicemia (A. veronii -liver disease, ICP most susceptible)
• osteomyelitis, pelvic abscesses, otitis, cystitis, etc.

Question 22

Aeromonas identification

Answer 22

beta hemolytic
oxidase positive
indole positive
string test negative
resistant to Vibriostat disk
grow well in 0% NaCl
inositol negative

Question 23

Aeromonas antimicrobial susceptibility

Answer 23

susceptible to trimethoprim, sulfamethoxazole (SMZ), aminoglycosides and quinolones

Question 24

Plesiomonas

Answer 24

• gram-negative rods (part of enterobacteriaceae)
• similar to Shigella, but lower virulence
• soil and aquatic environments

Question 25

Plesiomonas shigelloides

Answer 25

oxidase positive
ferments glucose
facultative anaerobe
motile (polar flagella)
susceptible to Vibriostat disk

Question 26

Plesiomonas shigelloides (clinical infections)

Answer 26

• gastroenteritis (undercooked seafood - diarrhea, subacute or chronic)
• extraintestinal infections (found in snakes, lizards, newts - zoo keepers at risk)
• mostly self-limiting

Question 27

Plesiomonas shigelloides (culturing)

Answer 27

• grow quickly on most media
• nonhemolytic colonies with raised center
• inositol brilliant green bile salts (IBB) - white or pink

Question 28

Differentiating Plesiomonas shigelloides

Answer 28

• 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

Question 29

Campylobacter

Answer 29

• microaerophilic (5% O2)
• non-spore forming rods (seagull-wing shape)
• oxidase and catalase +
• darting motility
• nonfermentative

Question 30

Campylobacter (clinical infections)

Answer 30

• 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

Question 31

Helicobacter pylori

Answer 31

• 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)

Question 32

Culturing Campylobacter and Helicobacter

Answer 32

• 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

Question 33

Presumptive ID of Helicobacter

Answer 33

• Inoculate Christensen’s urea medium - (rapid color change in 2 hours)
• biopsy stomach specimen
• urea breath test