Occurrence, diversity, and pathogenicity of halophilic Vibrio spp. and non-O1 Vibrio cholerae from estuarine waters along the Italian Adriatic coast

Abstract

The occurrence, diversity, and pathogenicity of Vibrio spp. were investigated in two estuaries along the Italian Adriatic coast. Vibrio alginolyticus was the predominant species, followed by Vibrio parahaemolyticus, non-O1 Vibrio cholerae, and Vibrio vulnificus. By using a biochemical fingerprinting method, all isolates were grouped into nine phenotypes with similarity levels of 75 to 97.5%. The production of toxins capable of causing cytoskeleton-dependent changes was detected in a large number of Vibrio strains. These findings indicate a significant presence of potentially pathogenic Vibrio strains along the Adriatic coast.

FIG. 1

Viable Vibrio spp. log₁₀ of CFU 100 ml⁻¹ (○), temperature (▴), and per mille salinity NaCl (□) measured monthly in the Metauro (a) and Foglia (c) estuaries. Viable Vibrio spp. log₁₀ CFU 100 ml⁻¹ (○), nutrient concentrations as total nitrogen micrograms liter⁻¹ (●) and phosphate micrograms liter⁻¹ (⧫) and as dissolved oxygen milligrams liter⁻¹ (▵) measured monthly in the Metauro (b) and Foglia (d) estuaries. All abiotic parameters were measured as previously reported by Fiorentini et al. (13).

FIG. 2

Dendrograms showing phenotypic similarity among isolated Vibrio strains of different species, their virulence properties, and sites and times of sampling. Abbreviations used: ID level, identity level; Hly, hemolysin; CT, cytotoxin; M and F, Metauro and Foglia estuary, respectively; S1 to S6, single PhP types; C1 to C9, common PhP types.

FIG. 3

Phase-contrast micrographs of HEp-2 cells exposed to bacteria (a to d) showing different patterns of adhesion (b and c) or cytotoxicity (d). Note the clustered bacterial distribution on the cells in panel b and the diffuse one in panel c. SEM of control CHO cells (e) and CHO cells after treatment with cytotoxic supernatant (f). Cytotoxicity due either to bacteria or to soluble bacterial products causes cell rounding (d and f). Bar, 10 μm.