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Vibriões e curvos

Vibrio cholerae

Curved, comma-shaped Gram-negative bacilli

Identification & Growth

Identification

  • Oxidase-positive, darting motility, grows without added NaCl
  • TCBS: yellow colonies (sucrose-positive); serogroups O1 and O139

Growth Conditions

  • Alkaline peptone water (pH 8.6) for 6–8 h then subculture on TCBS

Clinical Significance

  • Cholera: rice-water diarrhoea with rapid dehydration; immediate notification

Intrinsic Resistance

  • Polymyxin behaviour varies by serogroup; do not use it for therapeutic screening

Bench Alerts

  • Clinical suspicion must be communicated: TCBS is not routinely plated in stool cultures
  • Immediate compulsory notification and referral of the strain to the reference laboratory

Clinical Notes

Clinical presentations

  • Cholera: profuse rice-water watery diarrhoea without fever, causing severe dehydration within hours.
  • Vomiting, muscle cramps, metabolic acidosis and hypovolaemic renal failure.
  • Non-O1/non-O139 strains cause milder gastroenteritis, wound infection and bacteremia in patients with liver disease.

Specimens and collection

  • Fresh stool or rectal swab in Cary-Blair medium; collect before antimicrobials.
  • Plate on TCBS agar: V. cholerae produces yellow colonies through sucrose fermentation.
  • Alkaline peptone water as an enrichment broth increases recovery in paucibacillary samples.

Epidemiology and at-risk populations

  • Faecal-oral transmission through contaminated water and food, linked to poor sanitation and humanitarian emergencies.
  • The cholera-toxin-producing O1 and O139 serogroups are responsible for epidemics.
  • An internationally notifiable disease: notify the epidemiological surveillance service immediately.

Resistance and therapeutic implications

  • Oral or intravenous rehydration is the life-saving treatment; antimicrobials only shorten illness and shedding.
  • Single-dose doxycycline is the reference option in adults, with azithromycin as an alternative in pregnancy and children.
  • Resistance to trimethoprim-sulfamethoxazole and fluoroquinolones is increasing in epidemic strains: monitor the local profile.

Bench and reporting notes

  • Curved Gram-negative rod, oxidase-positive, with darting motility visible on wet mount.
  • Confirm the O1/O139 serogroup by slide agglutination and forward the isolate to the reference laboratory.
  • An immediately communicable result: inform the clinician and surveillance even before the formal report is released.

Sources

Educational decision-support content. It does not replace laboratory validation, current guidelines or review by the responsible professional.

FAQ: Frequently Asked Questions

How to identify Vibrio cholerae in the lab?

Vibrio cholerae is identified through oxidase-positive, darting motility, grows without added nacl, tcbs: yellow colonies (sucrose-positive); serogroups o1 and o139.

What are the intrinsic resistances of Vibrio cholerae?

This organism is naturally resistant to polymyxin behaviour varies by serogroup; do not use it for therapeutic screening. These drugs should not be reported as susceptible.

Where is Vibrio cholerae commonly found?

It is typically associated with cholera: rice-water diarrhoea with rapid dehydration; immediate notification.

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