Sanidade de ostras (CRASSOSTREA sp.) e parâmetros ambentais: diversidade microbiológica e qualidade da água em regiões portuárias.

Abstract

Understanding the role of microorganisms in aquatic organisms is essential for the ecology of these animals, as well as for their health. The aim of this research was to determine the microbiological diversity in oysters and to verify environmental microbiological parameters of the water in port areas located in the municipality of São Luís, state of Maranhão. Four collections were made to carry out the study. At the same time, the environmental variables of the water at the site were measured in relation to the hydrogen potential (pH), temperature (°C), salinity (ppt), dissolved oxygen (mg/L) and conductivity (uS/cm) with the aid of multiparameter equipment. Approximately 30 specimens of oysters were also collected during the dry and rainy seasons in Maranhão. For fungal analysis of the oysters, isolation was performed by serial dilution at 10-1, 10-2 and 10-3 in Potato Dextrose Broth (BD) followed by plating on Potato Dextrose Agar (PDA). For the identification of the fungal species, DNA extraction and amplification of the ITS1F and ITS4R regions were performed. And, for the bacteriological analysis of these organisms, conventional microbiology (isolation and identification) was performed for the sanitary hygienic indicators: viable strict and facultative aerobic mesophiles, coagulase-positive staphylococci (ECP), total and thermotolerant coliforms, Escherichia coli, Salmonella sp. and Vibrio. For the microbiological analysis of the water, 500 mL of water were collected in sterilized bottles for quantification of total coliforms and E. coli by the chromogenic (ONPG) and fluorogenic (MUG) enzyme substrate test. As a result, the growth of 69 yeasts and 29 filamentous fungi was observed among the isolates, allowing the identification of the fungal species: Meyerozyma carpophila, Pseudozyma sp., Pichia sporocuriosa, Fusarium sp., Curvularia geniculata, and Westerdykella dispersa. This research also provided pioneering results, such as the first report of the species of the fungus Trametes versicolor and the yeast Pichia kudriavzevii in oysters. The environmental variables measured showed variations in the sampling periods, but not significantly after being subjected to statistical tests. The results for the microbiological analysis of the water showed satisfactory values, in accordance with current Brazilian legislation, as well as the microbiological standards of the oyster samples regarding the studies of hygienic and sanitary indicators. It is concluded that the oyster environment is influenced by human actions, as demonstrated by the presence of yeasts and fungi. Although the bacteria levels are adequate to Brazilian regulatory parameters, it is essential to maintain permanent monitoring of the study area since the quality parameters may be influenced by climate and temporal variations.