Tracking of Clinical and Environmental Vibrio Cholerae O1 Strains by Combined Analysis of the Presence of Toxin Cassette, Plasmid Content and ERIC PCR

FEMS Immunol Med Microbiol. 1997 Sep;19(1):33-45. doi: 10.1111/j.1574-695X.1997.tb01070.x.


Clinical and environmental Vibrio cholerae O1 strains associated with the cholera epidemic in the Luanda province of Angola from 1991 to 1994 were tracked by toxin distribution, plasmid content and chromosomal polymorphism of the enterobacterial repetitive intergenic consensus (ERIC) sequences by PCR fingerprinting. To follow the distribution of ace, zot and ctxA toxin genes, 6 specific PCR tests were applied to 100 Vibrio strains, after preliminary hybridization experiments. Clinical isolates of Vibrio cholerae O1 were characterized by high stability of the toxigenic cassette and the presence of a large conjugative multi-resistant plasmid of incompatibility class C. Such characteristics were present in all isolates during the four years of the epidemic. Environmental strains, isolated from the river supplying water to the Luanda population showed three different genetic profiles: the presence of both cassette and plasmid, the presence of cassette only or absence of both. To assess the clonal relationship between the clinical isolates and the three groups of environmental strains, the strains were analyzed by PCR ERIC polymorphism. This analysis, supported by the toxin and plasmid content, suggested the stability of the epidemic strain in clinical cases during the epidemic and led to the finding that there was a strict genetic relationship of the epidemic strain with the environmental ones as characterized by the presence of the toxin cassette. The role of the water supply from Bengo River as a reservoir of the Vibrio epidemic strain is discussed.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Angola / epidemiology
  • Anti-Bacterial Agents / pharmacology
  • Cholera / epidemiology*
  • Cholera / genetics*
  • Cholera Toxin / genetics*
  • Chromosome Mapping
  • DNA Primers / genetics
  • DNA, Bacterial / analysis*
  • DNA, Bacterial / genetics
  • Disease Outbreaks
  • Humans
  • Microbial Sensitivity Tests
  • Molecular Epidemiology
  • Nucleic Acid Hybridization
  • Plasmids / genetics
  • Polymerase Chain Reaction
  • Polymorphism, Restriction Fragment Length
  • Repetitive Sequences, Nucleic Acid
  • Vibrio cholerae / drug effects
  • Vibrio cholerae / genetics*
  • Water Supply / analysis


  • Ace toxin
  • Anti-Bacterial Agents
  • DNA Primers
  • DNA, Bacterial
  • zonula occludens toxin, Vibrio cholerae
  • Cholera Toxin