VIBRIO, AERONOMAS, CAMPYLOBACTER

• Vibrio


  Genus of bacteria in the family Vibrionaceae, includes over 110 species, 10 of which have been found in human clinical specimens
• Vibrio


  • Found in a wide variety of aquatic environments including fresh water, brackish or estuarine water, and marine or salt water
  • Their numbers decline in winter months and are generally found only in sediments
  • Risk of infection can be reduced by avoiding raw or undercooked shellfish, especially in warmer months
• Pandemics (worldwide epidemics) of cholera caused by Vibrio cholerae have been documented since 1817
• In 2016, an outbreak of cholera in Tanzania caused 20,961 illnesses and 329 deaths
• In 2015, there were 172,454 cholera cases and 1304 deaths in 42 countries worldwide
• There has been an increased number of cases of Vibrio infections worldwide, both gastrointestinal and extraintestinal, caused by other Vibrio species
• Vibrio spp.


  • Asporogenous, gram-negative rods that measure approximately 0.5 to 0.8 µm in diameter by 1.4 to 2.6 µm in length
  • Most possess polar, sheathed monotrichous or multitrichous flagella
  • Can appear curved or comma-shaped but often appear as small, straight, gram-negative rods
• Vibrio spp.


  • Facultatively anaerobic
  • Catalase and oxidase positive
  • Able to reduce nitrate to nitrite, except for V. metschnikovii
  • Generally susceptible to the vibriostatic compound O/129
• Cholera


  Acute diarrheal disease caused by Vibrio cholerae, spread mainly through contaminated water
• Cholera toxin (choleragen)


  Powerful enterotoxin produced by V. cholerae that binds to GM1 ganglioside receptors on cell membranes, stimulating hypersecretion of electrolytes and water into the intestinal lumen
• Treatment of cholera involves administration of copious amounts of intravenous or oral fluids to replace fluids lost from severe diarrhea
• Antimicrobial therapy may also be used in the treatment of cholera
• Cholera toxin mechanism


  1. Toxin binds to GM1 ganglioside receptor on cell membrane via B subunits

  2. A1 subunit catalyzes ADP ribosylation of Gs regulatory protein, locking it in active state

  3. Persistent activation of adenylate cyclase

  4. Increased cAMP accumulation along cell membrane

  5. Increased secretion of Na+, Cl-, K+, HCO3- and water out of cell into intestinal lumen
• Vibrio cholerae O1


  • Causative agent of cholera
  • Epidemic cholera has been a disease of major public health significance for centuries
  • Most epidemics occur in developing countries where it is endemic, particularly in Bengal region of India and Bangladesh
  • Seventh and current pandemic originated in Indonesia in 1961 and spread throughout Asia and Africa
• Vibrio cholerae O139


  • Emerged in 1992, first V. cholerae non-O1 strain producing epidemic disease
  • Contains cholera toxin gene and causes disease resembling cholera caused by V. cholerae O1
• Vibrio parahaemolyticus


  • Second most common Vibrio species implicated in gastroenteritis after V. cholerae
  • Most frequently encountered Vibrio species in clinical samples in US
  • Primarily causes "summer diarrhea" in Japan
  • Isolated in Europe, Baltic area, Australia, Africa, Canada, and coastal US states
  • Pandemic strain of serotype O3:K6 emerged after 1996 and implicated in numerous foodborne outbreaks worldwide
• In 2014, CDC reported 605 cases of V. parahaemolyticus in US, with 86 hospitalizations and 4 deaths
• Vibrio alginolyticus


  • Least pathogenic Vibrio species for humans
  • Commonly isolated from extraintestinal sources like eye, ear, wound and burn infections
  • Can be an occupational hazard for people in constant contact with seawater
• Specimen collection and transport for Vibrio

  1. Body fluids, pus or tissues preferred, swabs acceptable if transported in holding medium like Cary-Blair

  2. Stool specimens should be collected early in illness and before antimicrobial treatment
• Culture media for Vibrio

  • Growth on SBA or CHOC agar - medium to large, smooth, opaque, iridescent colonies with greenish hue
  • On MacConkey agar, pathogenic Vibrio usually non-lactose fermenters
  • TCBS agar differentiates sucrose-fermenting (yellow) from non-sucrose-fermenting (green) Vibrio species
• Lactose-fermenting Vibrio species like V. vulnificus may be overlooked on MacConkey agar and mistaken for Enterobacteriaceae
• TCBS agar quality control must be stringent as there is great variation between lots in inhibition of other organisms
• Vibrio parahaemolyticus gastroenteritis


  • Generally self-limited with watery diarrhea, moderate cramps/vomiting, little fever
  • Symptoms begin 24-48 hours after ingesting contaminated seafood
• Kanagawa phenomenon


  Association between hemolysin production and virulence in V. parahaemolyticus
• Gastrointestinal disease caused by V. parahaemolyticus

  Generally self-limited, with watery diarrhea, moderate cramps or vomiting, and little if any fever. Symptoms begin about 24 to 48 hours after ingestion of contaminated seafood.
• V. parahaemolyticus has occasionally been isolated from extraintestinal sources such as wounds, ear and eye infections, and even cases of pneumonia. Invariably the patient has a history of recent aquatic exposure or a water-associated traumatic injury to the infected site.
• Pathogenesis of V. parahaemolyticus

  Not as well understood as V. cholerae. Possible association between hemolysin production and virulence, known as the Kanagawa phenomenon. Most clinical V. parahaemolyticus strains produce a heat-stable hemolysin that is able to lyse human erythrocytes in a special, high-salt mannitol medium (Wagatsuma agar). These strains are considered Kanagawa toxin-positive, whereas most environmental isolates are Kanagawa toxin-negative.
• There are exceptions to both these observations, and the exact role of this hemolysin in pathogenesis is still not understood.
• Recent emergence of atypical urease-positive V. parahaemolyticus strains from clinical sources along the Pacific coast of North America.
• Vibrio vulnificus infections


  Fall into two categories: primary septicemia and wound infections. Primary septicemia is thought to occur through the gastrointestinal route after the consumption of shellfish, especially raw oysters. Patients with liver dysfunction and syndromes that result in increased serum levels of iron are particularly predisposed. Wound infections invariably have a history of some type of traumatic aquatic wound that often presents as a cellulitis.
• Vibrio vulnificus infections can progress to necrotizing fasciitis and/or multiple organ system failure. The most serious cases are in immunocompromised individuals and those who have experienced a mild to severe injury to the infected site.
• In 2007, the CDC required that cases of V. vulnificus be reported to local and state public health departments.
• The patient in the Case in Point had a typical case history and clinical signs and symptoms of V. vulnificus infection. The patient suffered from posthepatic cirrhosis, a predisposing factor. In addition, he had suffered a minor wound after handling shellfish that rapidly developed into septic shock.
• It is important to use selective media and key biochemical reactions to differentiate Vibrio from Vibrio-like organisms. Key biochemical tests to differentiate various Vibrio spp. include reaction on TCBS, agent O/129 susceptibility or resistance, string test, and growth in different concentrations of NaCl.
• Rapid and semiautomated identification systems generally are inadequate for accurate identification of Vibrio species, particularly those that are less commonly encountered. Their inoculating suspensions should contain at least 0.85% NaCl, and the halophilic species might grow poorly, if at all.
• 16S ribosomal ribonucleic acid (rRNA) sequencing is an accurate way to identify most Vibrio spp.; however, because of their rare isolation, this method is infrequently used in clinical microbiology laboratories.
• Matrix-assisted laser desorption/ionization–time-of-flight (MALDI-TOF) mass spectrometry might become a rapid, cost-effective means of identification for Vibrio species.
• Pulse field gel electrophoresis is used for surveillance purposes. Ribotyping, multilocus sequence typing, and repetitive extragenic palindromic polymerase chain reaction PCR (REP-PCR) are also available for molecular typing of vibrios.
• It is generally considered sufficient for most clinical laboratories below the level of reference laboratory simply to screen their presumptive V. cholerae isolates with commercially available polyvalent O1 antiserum.
• Mueller-Hinton agar and broth contain sufficient salt to support the growth of Vibrio spp. most often isolated from clinical specimens. The recommended antimicrobial susceptibility testing methods are standardized disk diffusion (Kirby-Bauer) or dilution susceptibility testing methods.