Multi-drug resistant Vibrio cholerae O1 variant El Tor isolated in northern Vietnam between 2007 and 2010

Huu Dat Tran,Shah Manzur Rashed,Mohammad Ansaruzzaman,Heiman F L Wertheim,Van Ca Pham,Nguyen Van Kinh,Nurul A Bhuiyan,Nguyen Vu Trung,Hubert P Endtz,Munirul Alam,Hong Ha Nguyen,Tuyet Trinh Dao

doi:10.1099/jmm.0.034744-0

Abstract

Since 2007, there has been a re-emergence of cholera outbreaks in northern Vietnam. To understand the molecular epidemiological relatedness and determine the antibiotic susceptibility profiles of responsible V. cholerae O1 outbreak strains, a representative collection of 100 V. cholerae O1 strains was characterized. V. cholerae O1 strains isolated from diarrhoeal patients in northern Vietnam between 2007 and 2010 were investigated for antibiotic susceptibility and characterized by using phenotypic and genotypic tests, including PFGE analysis. Ten clinical V. cholerae O1 isolates from Bangladesh and Zimbabwe were included for comparison. The results revealed that all isolates were resistant to co-trimoxazole and nalidixic acid, 29 % were resistant to tetracycline and 1 % were resistant to azithromycin. All strains were susceptible to ampicillin–sulbactam, doxycycline, chloramphenicol and ciprofloxacin and 95 % were susceptible to azithromycin. MIC values did show reduced susceptibility to fluoroquinolones and 63 % of the strains were intermediately resistant to tetracycline. The isolates expressed phenotypic traits of both serogroup O1 Ogawa and El Tor and harboured an rstR El Tor and ctxB classical biotype. Among the outbreak isolates, only a single PFGE pattern was observed throughout the study period. This study shows that multi-drug resistant V. cholerae altered El Tor producing classical CT strains are now predominant in northern Vietnam.

Highlights

Cholera is an acute diarrhoeal disease, causing profuse watery stools, which, if untreated, leads to rapid dehydration and death (Kaper et al, 1995)
Results of Mismatch amplification mutation assay (MAMA)-PCR showed that all the V. cholerae isolates from Vietnam in this study harboured the ctxB1 allele which had been identified in strains of the classical biotype worldwide and in US Gulf Coast El Tor strains
Earlier work already showed that cholera outbreaks in northern Vietnam in 2007 and early 2008 were caused by a V. cholerae O1 El Tor variant biotype strain producing ‘classical’ CTXB

Summary

Introduction

Cholera is an acute diarrhoeal disease, causing profuse watery stools, which, if untreated, leads to rapid dehydration and death (Kaper et al, 1995). Cholera is caused by the Gram-negative bacterium Vibrio cholerae serogroups O1 and O139 (Kaper et al, 1995). Serogroup O1 can be categorized into two biotypes (classical or El Tor), and three serotypes. The seventh, and current, pandemic of cholera is being caused by the El Tor biotype while the fifth and sixth pandemics of cholera were caused by the classical biotype (Alam et al, 2010). New variants of V. cholerae O1 have emerged and spread throughout many countries of Asia, Africa and America that display a mixture of phenotypic and genotypic traits of both classical and El Tor biotypes (Alam et al, 2010; Ansaruzzaman et al, 2007)

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Conclusion