Data from: Cholera outbreaks (2012) in three districts of Nepal reveal clonal transmission of multi-drug resistant Vibrio cholerae O1

Background: Although endemic cholera causes significant morbidity and
mortality each year in Nepal, lack of information about the causal
bacterium often hinders cholera intervention and prevention. In 2012,
diarrheal outbreaks affected three districts of Nepal with confirmed cases
of mortality. This study was designed to understand the drug response
patterns, source, and transmission of Vibrio cholerae associated with 2012
cholera outbreaks in Nepal. Methods: V. cholerae (n = 28) isolated from
2012 diarrhea outbreaks {n = 22; Kathmandu (n = 12), Doti (n = 9), Bajhang
(n = 1)}, and surface water (n = 6; Kathmandu) were tested for
antimicrobial response. Virulence properties and DNA fingerprinting of the
strains were determined by multi-locus genetic screening employing
polymerase chain reaction, DNA sequencing, and pulsed-field gel
electrophoresis (PFGE). Results: All V. cholerae strains isolated from
patients and surface water were confirmed to be toxigenic, belonging to
serogroup O1, Ogawa serotype, biotype El Tor, and possessed classical
biotype cholera toxin (CTX). Double-mismatch amplification mutation assay
(DMAMA)-PCR revealed the V. cholerae strains to possess the B-7 allele of
ctx subunit B. DNA sequencing of tcpA revealed a point mutation at amino
acid position 64 (N [rightwards arrow] S) while the ctxAB promoter
revealed four copies of the tandem heptamer repeat sequence
5[prime]-TTTTGAT-3[prime]. V. cholerae possessed all the ORFs of the
Vibrio seventh pandemic island (VSP)-I but lacked the ORFs 498-511 of
VSP-II. All strains were multidrug resistant with resistance to
trimethoprim-sulfamethoxazole (SXT), nalidixic acid (NA), and streptomycin
(S); all carried the SXT genetic element. DNA sequencing and deduced amino
acid sequence of gyrA and parC of the NAR strains (n = 4) revealed point
mutations at amino acid positions 83 (S [rightwards arrow] I), and 85 (S
[rightwards arrow] L), respectively. Similar PFGE (NotI) pattern revealed
the Nepalese V. cholerae to be clonal, and related closely with V.
cholerae associated with cholera in Bangladesh and Haiti. Conclusions: In
2012, diarrhea outbreaks in three districts of Nepal were due to
transmission of multidrug resistant V. cholerae El Tor possessing cholera
toxin (ctx) B-7 allele, which is clonal and related closely with V.
cholerae associated with cholera in Bangladesh and Haiti.