Molecular characterisation of <it>Vibrio cholerae </it>O1 strains carrying an SXT/R391-like element from cholera outbreaks in Kenya: 1994-2007

• Main Authors: Goddeeris Bruno M, Saidi Suleiman M, Kiiru John N, Wamae Njeri C, Butaye Patrick, Kariuki Samuel M
• Format: Article
• Language: English
• Published: BMC 2009-12-01
• Series: BMC Microbiology
• Online Access: http://www.biomedcentral.com/1471-2180/9/275

<p>Abstract</p> <p>Background</p> <p>Over the last decade, cholera outbreaks in parts of Kenya have become common. Although a number of recent studies describe the epidemiology of cholera in Kenya, there is paucity of information concerning the diversity and occurrence of mobile genetic elements in <it>Vibrio cholerae </it>strains implicated in these outbreaks. A total of 65 <it>Vibrio cholerae </it>O1 El Tor serotype Inaba isolated between 1994 and 2007 from various outbreaks in Kenya were investigated for mobile genetic elements including integrons, transposons, the integrating conjugative elements (ICEs), conjugative plasmids and for their genotypic relatedness.</p> <p>Results</p> <p>All the strains were haemolytic on 5% sheep blood and positive for the <it>Vibrio cholerae </it>El Tor-specific haemolysin toxin gene (<it>hylA</it>) by PCR. They all contained <it>strB, sulII, floR </it>and the <it>dfrA1 </it>genes encoding resistance to streptomycin, sulfamethoxazole, chloramphenicol and trimethoprim respectively. These genes, together with an ICE belonging to the SXT/R391 family were transferable to the rifampicin-resistant <it>E. coli </it>C600 <it>en bloc</it>. All the strains were negative for integron class 1, 2 and 3 and for transposase gene of transposon <it>Tn</it>7 but were positive for integron class 4 and the <it>trpM </it>gene of transposon <it>Tn</it>21. No plasmids were isolated from any of the 65 strains. All the strains were also positive for all <it>V. cholera </it>El Tor pathogenic genes except the NAG- specific heat-stable toxin (<it>st</it>) gene. None of the strains were positive for virulence genes associated with the <it>V. cholerae </it>classical biotype. All the strains were positive for El Tor-specific CTXphi bacteriophage <it>rstrR </it>repressor gene (<it>CTX</it>^ET<it>Φ</it>) but negative for the Classical, Calcutta, and the Environmental repressor types. Pulse Field Gel Electrophoresis (PFGE) showed that regardless of the year of isolation, all the strains bearing the SXT element were clonally related.</p> <p>Conclusions</p> <p>This study demonstrates that the <it>V. cholerae </it>O1 strains carrying an SXT/R391-like element implicated in recent cholera outbreaks in Kenya has not changed significantly between 1994 and 2007 and are clonally related.</p>