Emergence of Vibrio cholerae O1 classical biotype in 2012 in Iran

Abstract

Cholera outbreaks annually occur in many parts of Iran. The aim of this study was to investigate the biotype and genotype diversity of V. cholerae isolates from recent outbreak (2012) in Iran and to characterize the ctxB allelic sequence of isolates. The ctxB sequence of all isolates was analyzed and compared with the reference ctxB sequences for El Tor and classical biotypes in GenBank database. The PFGE genotype specification of isolates was determined and genetic relatedness among isolates and also with those previously reported from Iran was assessed. Ten out of eleven isolates were identified as El Tor biotype and one single isolate belonged to classical biotype. All isolates except three possessed tcpA, ctxA, ctxB and wbeT genes. All the ctxB(+) isolates in this study (classical and El Tor biotypes) possessed the ctxB sequence of classical biotype allele providing evidences of El Tor variants. Eight out of 11 isolates (73%) showed identical pulsotypes (P1). Each of the remaining three isolates showed distinct pulsotypes (P2-P4) with more than three band differences. Pulsotype P2 was corresponded to an isolate (9%) with classical biotype. The result demonstrated diversity in virulence gene content of strains with identical PFGE patterns and also provided evidences of the import of a V. cholerae strain with classical biotype from out of our country as no classical biotype strain has been previously (1998-2011) reported from Iran. Emergence of V. cholerae with Classical biotype after at least one decade in Iran is alarming due to fear of expansion of V. cholerae strains with high virulence potential and signifies the need to monitor and analyze all new cases in countries with cholera outbreaks or even sporadic cases as this could conceivably affect the neighbouring countries and may expose the world to the seventh pandemic with Classical biotype strains.