Abundance of hybrid genomes among Vibrio cholerae in the aquatic environment determined by fluorescence labelled gene cassette PCR and pulsed field gel electrophoresis: An Australian perspective

Vibrio cholerae is the causative agent of cholera, a life threatening and watery diarrhoea that causes an estimated 3–5 million cholera cases and100000–120000 deaths per year (Zuckerman et al., 2007). The current pandemic of cholera is caused by El Tor biotype of the O1 serotype distinct from the classical biotype that is responsible for the previous pandemics. Recently, V. cholerae strains isolated from Asia and Africa have been reported to harbour phenotypic and genotypic characteristics (Nair et al.,2002 ; Safa et al., 2005; Safa et al., 2009) from both the classical and El Tor (ET) biotypes suggesting that they are genetic hybrids (Safa et al., 2009). These hybrid strains possess all the necessary virulence genes and genetic traits leading to fears that these strains may initiate a new pandemic. The fact that the V. cholerae hybrid strains possess characteristics related to the classical biotype is noteworthy since the classical biotype was believed to be extinct (Safa et al., 2009). The types of V. cholerae residing in the aquatic environment of Sydney, Australia and its relatedness to known strains remains unknown due to the lack of bacteriological and molecular investigations. Using a new technique profiling integron-associated gene cassettes PCR (Labbate et al., 2007) and Pulse Field Gel electrophoresis (PFGE), we provide evidence for the environmental presence of V. cholerae in Sydney with relatedness to characterized hybrid strains.