Cholera: Diagnosis and Testing in Haiti

Laboratory Diagnosis

Laboratory Test Results of Cholera Outbreak Strain in Haiti Announced

Growth of V. cholerae on thiosulphate citrate bile salt sucrose agar  (TCBS)
Photo Credit: Centers for Disease Control and Prevention Atlanta, Georgia 1999

Culture: Vibrio cholerae (V. cholerae) is confirmed through culture from stool or rectal swabs. For isolation and identification, a selective medium, thiosulfate citrate bile salts (TCBS) agar is used and the serogroup and serotype is confirmed using V. cholerae specific antisera.

Antibiotic Susceptibility Testing: Many bacteria, including V.  cholerae, show resistance to some antibiotics used to treat illnesses. It is important for clinicians to understand what drugs various bacteria are typically resistant to in order to prescribe effective treatment regimens. In addition, related bacteria usually show similar resistance patterns. Bacterial drug resistance can be tested in the laboratory. Bacteria are exposed to various concentrations of multiple antibiotics. Bacteria that grow are considered resistant whereas bacteria that do not grow are considered susceptible.

Antibiotic susceptibility testing requires several days to perform. Antibiotic susceptibility testing of selected isolates provides information that helps inform recommended antibiotic therapy for treating a population. However, it is not recommended for guiding care for individual patients.

The V. cholerae isolates from people with cholera in Haiti have undergone antimicrobial susceptibility testing.

Scanning electron micrograph of V. cholerae bacteria
Photo Credit: Centers for Disease Control and Prevention Atlanta, Georgia 2005

Current antibiotic testing results show*:

*Susceptibility testing of selected isolates from ill patients in Haiti will continue, and clinicians should be alert for changes in antibiotic treatment recommendations based on clinical experience in Haiti.
**Susceptibility inferred based on tetracycline testing.

Rapid Tests:  Commercially available rapid immunochromatographic test kits for stool antigen are useful in epidemic settings but do not yield an isolate for antimicrobial susceptibility testing and subtyping, and should not be used for routine diagnosis.