Microbiological quality of oysters and water in macromarine mangrove swamps of the Amazon coast (Island of São Luís, MA), Brazil

ABSTRACT

In order to evaluate the microbiological quality of water and oysters from natural banks and oyster farms located on the Island of São Luís, Maranhão (MA), 60 samples were analyzed from September 2020 to February 2021, 30 of water and 30 of oysters (Crassostrea sp.), collected directly from shellfish farmers and owners of oyster farms in the municipalities of the Island of São Luís, MA. For the determination of total coliforms and Escherichia coli in the water samples the Colilert® rapid method was used. For the enumeration of total and thermotolerant coliforms in oysters the Most Probable Number (MPN) method was used and E. coli by biochemical tests (Indol, MV, VP, Citrate). The enumeration of coagulase positive Staphylococcus was performed using Baird Parker medium for isolation and identification, as well as biochemical tests. The geometric mean result of E. coli counts in the water samples ranged from 604.3 to 1,130.8 MPN/100mL, indicating unsatisfactory microbiological quality. As for the oyster samples, 8 (26.7%) out of 30 samples were unfit for consumption, and 4 (13.3%) were contaminated by Salmonella sp. and E. coli, respectively. According to RDC No. 331/19 and IN No. 60 of ANVISA, the results are worrisome for public health and mitigating actions are recommended, such as regular monitoring of the microbiological quality of the water.

Keywords:
oyster farming; Crassostrea sp.; public health; microorganisms