Classical RS1 and environmental RS1 elements in Vibrio cholerae O1 El Tor strains harbouring a tandem repeat of CTX prophage: revisiting Mozambique in 2005.

Currently, Vibrio cholerae O1 serogroup biotype El Tor strains producing classical type cholera toxin (altered strains or El Tor variants) are prevalent in Asia and in Mozambique. Mozambican strains collected in 2004 contained a tandem repeat of CTX prophage on the small chromosome and each CTX prophage harboured the classical rstR and classical ctxB. We found that the majority of the strains collected in 2005 in Mozambique contained extra elements on the large chromosome in addition to the tandem repeat of CTX prophage on the small chromosome. New type RS1 elements RS1(cla) and RS1(env), and a CTX(env) with rstR(env) and the classical ctxB were identified on the large chromosome of the Mozambican isolates collected in 2005.