Table 1.

Distribution of major virulence-associated genes among nontoxigenic Vibrio cholerae O1 and non-O1 strains isolated from cholera patients or environmental surface water and susceptibility of the strains to a genetically marked derivative of CTXΦ

V. cholerae serogroupCountryYr of isolationSourceNo. of strainsPresence ofa:No. of strains
ctxAzotacetcpAtcpIacfBtoxRattRSInfected with CTX-KmΦbLysogenizedc
O1, El Tor biotype
India1993Patient6+++++66
Estonia1995SWd 3+00
Latvia1995SW1+00
Saudi Arabia1997Patient4+++++44
Non-O1, non-O139
Saudi Arabia1997Patient1+00
Saudi Arabia1997Patient2++00
Bangladesh1992–1995SW3+00
Bangladesh1992–1995SW1900
Bangladesh1994–1996SW23++00
Bangladesh1993–1996SW84+10
  • a The presence of different genes was detected with DNA probes and PCR assays (see the text for details). The size of the PCR-generated amplicon corresponding to the tcpAgene was characteristic of that of the El Tor biotype.

  • b Susceptibility to the phage was determined with a genetically marked phage, CTX-KmΦ (see the text for details).

  • c Integration of the phage genome into the host chromosome was determined by Southern blot analysis of genomic and plasmid DNA isolated from native and infected strains.

  • d SW, surface water.