Concomitant infection of enterotoxigenic Escherichia coli in an outbreak of cholera caused by Vibrio cholerae O1 and O139 in Ahmedabad, India

In Ahmedabad, a major city in the state of Gujarat, India, an outbreak of a cute secretory diarrhea caused by Vibrio cholerae O1 Ogawa El Tor, V. chole rae O139, and multiple serotypes of enterotoxigenic Escherichia coli (ETEC) occurred in January 2000. All of the representative V. cholerae O1 and O13 9 isolates examined harbored the ctxA gene (encoding the A subunit of chole ra toxin) and the El Tor variant of the tcpA gene (encoding toxin-coregulat ed pilus). ETEC isolates of different serotypes were positive for the elt g ene, encoding heat-labile enterotoxin. To further understand the molecular characteristics of the pathogens, representative isolates were examined by ribotyping and pulsed-field gel electrophoresis (PFGE). Ribotyping showed t hat the isolates of V cholerae O1 Ogawa. exhibited a pattern identical to t hat of the prevailing clone of O1 in areas where cholera is endemic in Indi a, and all of the O139 isolates were identical to the BII clone of V. chole rae O139. PFGE of the representative O1 Ogawa isolates exhibited an identic al pattern, comparable to the H pattern of the new clone of O1 reported in Calcutta, India. PFGE analysis of the V. cholerae O139 isolates showed iden tical patterns, but these differed from the PFGE patterns of O139 isolates reported during 1992 to 1997 in Calcutta. ETEC isolates showed genetic hete rogeneity among isolates belonging to the same serotype, although the ident ical PFGE pattern was also observed among ETEC isolates of different seroty pes. Antibiograms of the isolates were unusual, because all of the O139 iso lates were resistant to nalidixic acid. Likewise, all of the E. coli isolat es showed resistance to ciprofloxacin, norfloxacin, and nalidixic acid. Thi s is a unique outbreak, and we believe that it is the first in which V. cho lerae and ETEC were concomitantly involved.