Re-emergence of Vibrio cholerae O139 in Pakistan: report from a tertiary care hospital.

OBJECTIVE This study reports re-emergence of Vibrio cholerae O139 in Pakistan in 2000-2001 from a tertiary care hospital in Karachi, Pakistan. METHODS This descriptive study was conducted from 2000-2001. Stool samples were taken from inpatients or those referred to the laboratory from other hospitals, clinics and general practitioners. Samples were processed and Vibrio cholerae isolates were identified according to standard protocols. Tellurite Taurocholate Gelatin agar was used as a selective medium for Vibrio cholerae. Serogroups were identified by slide agglutination with polyvalent antisera. Antimicrobial sensitivities were performed by Kirby Bauer technique. Data was entered and analyzed using SPSS, p values were calculated using t test and two independent samples test. RESULTS During the study period, 144 samples were found to be infected with Vibrio cholerae O139 in comparison with 545 Vibrio cholerae O1. Infection with O139 was characteristically observed in the older population (mean age = 40 years) in contrast with Vibrio cholerae O1 strains (mean age = 23 years) (p. value = <0.001). Sensitivity pattern of 2000-2001 Vibrio cholerae isolates was markedly different to that of 1993-1994. The earlier isolates were resistant to Cotrimoxazole (99%) and Chloramphenicol (35%) whereas the recent isolates are almost 100% sensitive. CONCLUSION In conclusion this re-emergent strain seen 6 years after previous episode infected large number of people especially older population suggesting that prior infection with O1 does not provide immunity against O139 and therefore Vibrio cholerae O139 has a potential to cause a major epidemic in an immunologically naïve population.