Species diversity, spatial distribution, and virulence associated genes of culturable vibrios in a brackish coastal Mediterranean environment

The Vibrio genus is widespread in marine and brackish environments, and several species are human and animal pathogens of global importance. Vibrios adapt rapidly to many environmental stresses, so that brackish environ- ments can be both a suitable niche and a possible reservoir for them. To test the occurrence of culturable vibrios and their possible correlation with environmental factors in a temperate brackish environment, a 1-year sampling study was performed in three brackish ponds located along the Central Thyrrenian coast in the Macchiatonda Nature Reserve (Santa Marinella, district of Rome, Italy). Molecular methods were used to de- tect Vibrio cholerae, V. parahaemolyticus, and V. vulnificus pathogenicity-associated genes among the Vibrio isolates. Out of 130 Vibrio isolates identified by sequencing a recA fragment, 70 harbored virulence-associated genes including ctx, ace, tcpA, tdh, trh, vvhA, vllY, and toxRS, so confirming the spread of virulence determinants across the environmental isolates. Ecological analysis showed that, although the water temperature is known to be a strong predictor of abundance and distribution of vibrios, its influence accounts for 27 % of the observed variance in the Macchiatonda samples, increas- ing to 40 % when combined with salinity.