Evaluation of the bacteriological quality of Crassostrea gigas implanted in the estuary of Bahia Blanca, Argentina

The Pacific oyster, Crassostrea gigas was introduced into many coastal ecosystems of Argentina. Its range of distribution in Bahia Blanca's estuary is uncertain, and there is evidence of its continued expansion. The aim of this work was to evaluate the bacteriological quality of the oyster in the inner area of the estuary of Bahia Blanca, and of the water and sediments where it grows. Two sampling stations were established: Club Nautico (CN) and Puerto Cuatreros (PC). Subsurface water, surface sediments and oysters were collected from the intertidal zone from June 2015 to June 2018. In the three matrices, counts of Escherichia coli (Ec) and detection of Vibrio spp. were done. In addition, Salmonella spp. was searched in the oyster tissue. In the two stations, an accumulation of Ec in oysters and in sediments was evidenced. In addition to the high values of Ec in CN, the presence of Salmonella in oysters was detected. In all the matrices of both stations Vibrio spp. were isolated, including V. cholerae and V. parahaemolyticus. The oyster beds studied in the estuary are a very accessible place and the specimens are of good size, make them attractive for informal harvesting. However, according to the bacteriological results, 66 % of the samples of PC oysters and 100 % of CN do not comply with the current legislation in Argentina, representing a potential risk for human health.