Vibrio cholerae O1 detection in estuarine and coastal zooplankton

Vibrio cholerae is an autochthonous marine bacterium, and its association withdiverse planktonic crustaceans has been extensively investigated; however, the pres-ence of V. cholerae on individuals of most phyla of planktonic animals is still incom-pletely understood. The objective of this study was to analyze the distribution ofV. cholerae serogroup O1 associated with specific zooplankton taxa in an estuaryand the adjacent continental shelf of the southeastern Brazilian coast. The occur-rence of the bacterium was assessed in zooplankton samples, specifically on themost abundant taxa, using direct fluorescence assay (DFA) and direct viablecount–direct fluorescence assay (DVC–DFA) methods. Vibrio cholerae O1 wasdetected in 88% of samples collected from the Santos-Bertioga estuary and in67% of samples from the shelf. The salinity of the estuarine water ranged from21.8 to 34.6, significantly lower than the shelf water which was 32.1–36.1.Salinity was the only environmental variable measured that displayed a significantcorrelation with the presence of V. cholerae (P , 0.05). Vibrio cholerae O1 was detectedin chaetognaths, pluteus larvae of echinoderms and planktonic fish eggs(Engraulidae), all new sites for this bacterium.KEYWORDS: plankton; estuary; DFA; Southwest Atlantic