Vibrio, Aero, and Campy Objectives

Describe the oxidase, glucose utilization, motility, transmission, and disease syndromes of Vibrio and Aeromonas

• GN bacilli

• Oxidase (+)

• Ferment glucose

  • Enterobacteriaceae are glucose fermenters but are oxidase (-)

• Motile with polar flagella

• Transmission:

  • Exposure to fecal-contaminated water

  • Ingest contaminated water or raw/undercooked fish, shellfish

• Disease syndromes

  • GI: Diarrhea

  • Extra-Intestinal: Trauma associated with exposure to H₂O (Wounds, Cellulitis, Otitis, Conjunctivitis, Septicemia)

For Vibrio: Describe the characteristic morphology and type of motility

GN curved bacilli (like commas)

Darting motility because of 1 flagella

For Vibrio: Define halophilic and name the two species that are not halophiles

• Halophile = Salt loving, require media with 1-2% NaCl

• All vibrio except V. cholerae and V. mimicus are halophilic

For Vibrio: Name the 2 biotypes, 2 serogroups and 3 serotypes of Vibrio chloerae

• Biotypes: Based on phenotypic characteristics, both agglutinate type O:1 antiserum

  • Classical

  • El Tor – Most current epidemics

• Serogroups: Based on O antigens (1-140)

  • O:1 – Epidemics and pandemics

  • O:139 – New epidemic strain (1992)

• Serotypes: Only in O:1 serogroup (Inaba, Ogawa, Hikojima (rare))

For Vibrio: Describe the reservoir and major sources of cholera

Humans only

Transmission: Human fecal contaminated food and water (poor sanitation), raw/undercooked fish/shellfish

For Vibrio: Describe the activity of the choleragen in cholera

• A/B toxin, enterotoxin

  • 2 A subunits, 5 B subunits

  • Phage mediated toxin, lysogenic bacteriophage

• Stimulates persistent activation of adenyl-cyclase → Accumulation of cAMP → Hypersecretion of water and electrolytes → Massive dehydration event

For Vibrio: Describe the symptoms and appearance of stool in cholera

• Abrupt onset: Vomiting, profuse diarrhea, afebrile

• Major fluid loss (15-20 L/day)

  • Hallmark = “Rice water” stool

  • Dehydration with electrolyte balance → Metabolic acidosis → Cardiovascular collapse and renal failure

• 60% mortality in untreated cases

For Vibrio: State the recommended treatment for cholera

• Replace fluids and electrolytes

• Tetracycline/doxycycline, SXT

• Vaccine for travelers = Vaxchoera

  • Single-dose, oral

  • Live, attenuated

For Vibrio: Describe the highly fatal infection associated with V. vulnificus

• Ingestion: Fatal septicemia with bullous lesions

• Wound infections → Necrotizing fasciitis

For Vibrio: Describe the selective-differential medium for isolation of vibrios

• Thiosulfate Citrate Bile salts Sucrose (TCBS): Selective-differential media for sucrose fermenters, very selective for vibrios

• Yellow colonies = sucrose (+)

For Vibrio: State the general characteristics of V. cholerae

• Oxidase (+)

• NLF on MAC (Clear), yellow on TCBS (sucrose fermenter)

• Kanagawa negative

• Not halophilic:

  • 0% NaCl = G

  • 1-6% NaCl = V

• Serotyping confirmation with O:1/O:139 antisera → No agglutination report V. cholerae non-O:1

For Vibrio: State the general characteristics of V. parahaemolyticus

• Oxidase (+)

• NLF on MAC, green on TCBS (sucrose negative)

• Kanagawa positive (β-hemolytic on HBA)

• Halophilic

For Vibrio: State the general characteristics of V. vulnificus

• Oxidase (+)

• LF on MAC (pink), 85% green on TCBS (sucrose negative)

• Halophilic

For Aeromonas: Describe the reservoirs and sources/transmission

• Reservoirs: Humans, dog, cat, pigs, reptiles, fish, amphibians, leeches

• Sources/Transmission:

  • Ingest fecal contaminated food and water (Fish, shellfish, dairy, fresh produce)

  • Trauma associated with water

  • HAI

    • Isolated from sink-traps, faucets, drains, dH2O, medicinal leeches

For Aeromonas: Describe associated infections

• GI: Diarrhea

  • Dysentery stool may be present (blood and mucus)

• Extra-Intestinal:

  • Wounds (cellulitis → necrotizing fasciitis)

  • Eye, ear

  • Immunocompromised = Septicemia, meningitis, endocarditis

• DOC: SXT, gentamicin, ciprofloxacin

For Aeromonas: Differentiate Aeromonas from Vibrio, based on gram morphology, appearance on enteric media, and salt-requirement.

Aeromonas:

• GN straight bacilli

• HEK: NLF

• Not halophilic

Vibrio:

• Curved bacilli with darting mobility

• HEK: Green (NLF)

• All vibrios except V. cholerae and V. mimicus are halophilic

For Aeromonas: State why Aeromonas hydrophila can be confused with E. coli, and the key test to correctly identify A. hydrophila.

Same: β-hemolytic, can be LF, indole (+)

But Aeromonas is oxidase (+)

For Campylobacter: Define microaerophilic

Organism that needs low level of oxygen for optimal growth

For Campylobacter: Describe gram morphology, motility, glucose utilization, and growth requirements of enteric campylobacters.

• GN curved bacilli (spiral, S shape, “seagull wings”)

• Darting motility

• Non-saccharolytic (does not ferment or oxidize glucose)

• Non-Halophilic

For Campylobacter: State the major sources and transmission in the U.S.

• Reservoirs: GI tract animals

  • Poultry, pigs, cattle, sheep, dogs cats

• Transmission:

  • Ingest poultry (50%), unpasteurized dairy, water

  • Direct contact: Pets, domestic animals

  • Person-Person

  • STI

For Campylobacter: Describe the typical colony morphology of C. jejuni on Campy-BA.

• Moist, yellow gray

• Non-hemolytic

• “Runny” along streak line

For Campylobacter: State test results for presumptive identification of C. jejuni

• Curved GN

• Typical morphology on Campy-BA:

  • Moist, yellow gray

  • Non-hemolytic

  • “Runny” along streak line

• Biochemical:

  • Catalase (+)

  • Oxidase (+)

  • Hippurate Hydrolysis (+)

For Campylobacter: State the treatment of choice for C. jejuni intestinal disease.

• Diarrhea: No antimicrobials unless septic

• Extra-Intestinal: Azithromycin, Erythromycin, Fluoroquinolones

For Helicobacter pylori: Describe gram morphology, motility, and growth requirements.

• GN spiral or curved

• Corkscrew motility

• Optimal growth @ 35C, microaerophilic

For Helicobacter pylori: Explain the adaptation to survive the acidic pH of the stomach.

Urease production → Ammonia → Neutralize gastric acidity

For Helicobacter pylori: State sources and transmission

• Reservoir: Humans only

  • Colonizes intestines in 50% of world population

  • 80-90% in developing countries

• Transmission: Fecal-oral, oral-oral, gastric-oral

For Helicobacter pylori: Name the associated disease syndromes

• Acute gastritis: Rarely diagnosed, usually left to run its course

• Chronic gastritis: 85% asymptomatic or mild

• Peptic and duodenal ulcers (90-95%)

  • Ammonia damages mucosa

  • Produces cytotoxins and enzymes → Weakens gastric mucosa → Ulcer

• Gastric adenocarcinoma: Only bacteria classified as Group 1 human carcinogen by WHO

For Helicobacter pylori: Compare and contrast invasive vs. non-invasive tests, including principle of test and usefulness in diagnosis and test of cure

Invasive:

• Gastric biopsy with endoscopy

• Histopathology is gold standard

Non-Invasive:

• Recommended by American College of Gastroenterology

  • Diagnostic += active infection

  • Test of cure after treatment

  • Sensitivity and specificity high

• EIA stool antigen: Detects antigen released from organisms lining stomach wall

• Urea breath test (UBT): Radioactive carbon (¹³C) urea ingested → Urea degraded by H. pylori → ¹³CO₂ detected via mass spectrometry

  • Expensive