Genomic diversity of clinical and environmental Vibrio cholerae strains isolated in Brazil between 1991 and 2001 as revealed by fluorescent amplified fragment length polymorphism analysis

Abstract

Vibrio cholerae is a ubiquitous and abundant organism in aquatic environments, particularly in coastal areas, estuaries, and rivers. This organism was the cause of a considerable number of deaths in Brazil during the last decade. In this study we applied the genomic fingerprinting technique fluorescent amplified fragment length polymorphism (FAFLP) to analyze 106 V. cholerae O1 and non-O1 and non-O139 strains isolated from clinical specimens and the environment between 1991 and 2001. Numerical analysis of the FAFLP patterns disclosed seven main groups of genomes, all of them originated from a variety of different places in different years, suggesting that V. cholerae is a very diverse species. O1 and non-O1 and non-O139 strains were distinguishable by FAFLP, although clinical and environmental strains clustered together in a few cases. The persistence of some strains of highly related genomes during several years and in completely different geographical regions suggests that these strains are highly successful in adapting to changing environmental conditions.

FIG. 1.

Dendrogram derived from FAFLP patterns of 106 V. cholerae strains with the ApaI/TaqI enzyme combination. The dendrogram was constructed by using the Pearson coefficient and the unweighted pair group method of arithmetic averages. V. mimicus LMG 7896^T was included as an out-group. The year, place, and source of isolation of strains are listed. C and E mean clinical and environmental isolates, respectively. Cophenetic correlation values are shown on the left.

FIG. 2.

Three-dimensional representation of PCA derived from the FAFLP patterns (24 ± 4 bands) of 106 V. cholerae strains. Black dots indicate O1 strains while white and grey dots indicate non-O1 strains and strains of other serogroups, respectively.