Colonization of Vibrio cholerae among persons in contact with cholera patients.

Abstract

Sir: Cholera is a major health problem in Myanmar. Until the 6th pandemic, cholera was caused by Vibrio cholerae O1 classical biotype (1). In 1961, the 7th pandemic of cholera began, and unlike the previous pandemics, this was caused by V. cholerae El Tor. In 1992, an epidemic of a cholera-like disease, caused by V. cholerae O139 synonym Bengal, occurred in Bangladesh and India (2). V. cholerae O139 strain was first identified in Myanmar in 1994 as isolated cases in an endemic pattern (3). V. cholerae O139 has since then become one of the casual pathogens in Myanmar. Cholera is transmitted from patients and convalescent carriers to the persons having intimate contacts and to the community through direct and indirect modes of transmission. Intra-familial spread of infection mainly occurs in the range of 4-22% and sometimes as high as 50% (4). Thus, to know the colonization of V. cholerae among persons in contact with cholera patients, this study was carried out. The study was conducted in Yangon from January to September 1999. Rectal swab samples were collected from 50 lactating mothers and 50 children aged less than two and a half years, who were either from families of hospitalized patients or from their neighbouring houses. V. cholerae O1 and O139 were confirmed in the index cases by culture and serotyping at the Infectious Diseases Hospital Laboratory in Yangon. With informed consents, rectal swabs were collected on day 1, day 5, and day 10 in sterile bottles, containing alkaline peptone water and were labelled. These were transported to the laboratory and were processed within one hour after arrival. In total, 300 rectal swab samples were examined. The rectal swab from alkaline peptone water (pH 8.4 with 0.5% NaCl) was plated onto alkaline nutrient agar (pH 8.4) and was incubated at 37[degrees]C overnight. After incubation, subculture was done, and then second alkaline peptone water was incubated for enrichment of organism. Finally, subculture was done from the second enrichment media. After overnight incubation at 37[degrees]C, convex and smooth round colonies that are opaque and granular in transmitted light were picked out, and biochemical reactions, oxidase reaction, and serotyping were done. Serotyping of the isolated strains was done with polyvalent V. cholerae O1 antisera and then with V. cholerae O1 (Inaba and Ogawa antisera) by slide agglutination test. If agglutination did not occur with polyvalent O1 antisera, serotyping was done with V. cholerae O139 antiserum. Of the 300 samples tested, one lactating mother and two breastfed children were found to have V. cholerae O1 Ogawa serotype, two lactating mothers and two breastfed children had V. cholerae O139, four lactating mothers and two breastfed children had V. cholerae non-O1 and non-O139, and one breastfed child had Vibrio spp. non-typeable. These were isolated from persons with contacts of proven V. cholerae O1 patients (Table). Similarly, among the contacts of index cases with V. …