Vibrio cholerae, Staphylococcus aureus and bacterial pathogenesis

Sequence analysis of Vibrio cholerae orfU and zot from pre-CTXΦ and CTXΦ reveals multiple origin of pre-CTXΦ and CTXΦ: A multiplex PCR was developed to detect pre-CTXΦ and CTXΦ in V. cholerae. A total of 115 V. cholerae were tested, of which 42 V. cholerae O1 and 18 V. cholerae O139 contained CTXΦ. Six V. cholerae O139 contained only pre-CTXΦ and three V. cholerae O1 and 23 V. cholerae O139 contained both pre-CTXΦ and CTXΦ. None of the V. cholerae non-O1 and non-O139 that were tested had pre-CTXΦ or CTXΦ. Results of RFLP analysis revealed the V. cholerae isolates possessed single or multiple copies of pre-CTXΦ and CTXΦ, always proceeded by a tandemly arranged RS1 element. Comparative nucleotide sequence analyses of the core region genes, orfU and zot, of 15 V. cholerae showed pre-CTX^ETΦ and CTX^ETΦ lineage with V. cholerae El Tor and pre-CTX^ClassΦ, pre-CTX^CalcΦ, and CTX^CalcΦ with classical V. cholerae O1 and O139. Two distinct types of ctxB were detected in V. cholerae O139. MLST of seven V. cholerae housekeeping genes indicated clonal origin, irrespective of the presence of pre-CTXΦ and/or CTXΦ.

Effect of storage and sodium chloride on excision of CTXФ or pre-CTXФ and CTXФ from Vibrio cholerae O139 strains: We examined the effect of storage and sodium chloride on excision of CTXФ or pre- CTXФ and CTXФ from Vibrio cholerae O139 strains. We found that one strain of V. cholerae O139 VO146P showed loss of the complete phage array, and other strain VO170P showed partial loss of the phage array giving rise to altered strains designated as VO146N and VO170N. Results of PCR and RFLP analysis revealed that both strains (VO146P and VO170P) possessed a single copy of pre-CTX^ETΦ and two copies of CTXΦ comprising CTX^ClassΦ and CTX^CalcΦ arranged in tandem, and integrated in the large chromosome. The presence of classical ctxB was detected in CTX^CalcΦ of both V. cholerae O139 strains. Nucleotide sequencing of three housekeeping genes showed no difference between parent and altered strains of V. cholerae O139.