Vibrios

Vibrios are part of the native microbiota of marine

environments and organisms. Up to 40% of water-column

bacteria are associated with zooplankton. Among these, vibrios

have a competitive advantage in the colonization of chitinous

exoskeletons1. Due to their abundance in the water column,

vibrios may be up to a hundred times more concentrated in

filter-feeding mollusks than in the immediate environment2.

Since vibrios are part of the autochthonous bacterial

community colonizing bivalves, it comes as no surprise

that they have been implicated in many outbreaks related to

oyster consumption. The vibrio species most often associated

with disease from consumption of oysters in natura are

Vibrio parahaemolyticus, V. vulnificus, and V. cholerae3.

However, virulence factors similar to those displayed by

V. parahaemolyticus are detected in other vibrio species with

increasing frequency. Thus, Nishibuchi et al.4 found that

V. hollisae strains from clinical samples can carry the hemolysinencoding

gene tdh, a marker of virulence. Other vibrio species

isolated from marine organisms have also been shown to be

capable of β-hemolysis5.

The objective of the present study was to survey the

Vibrio microbiota of fresh and frozen oysters (Crassostrea

rhizophorae) obtained from restaurants in Fortaleza, and to

identify phenotypical virulence factors by testing strains for

β-hemolysis and urease activity.

The study was based on 15 samples of fresh oysters and 15

samples of frozen oysters (C. rhizophorae) obtained from two

restaurants in Fortaleza City (Northeastern Brazil) between

August 2009 and August 2010. Each sample consisted of 10