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Bacterial contamination indices in the oyster Crassostrea cf. corteziensis from Portovelo, Río Chone estuary, Manabí, Ecuador

Abstract:

The Portovelo oyster (Crassostrea cf. corteziensis) from the Chone River estuary, Manabí province, Ecuador, is an item of artisanal exploitation and commercial sale for consumption (particularly raw), without knowing its microbial load. During one year, the microbiological quality (aerobic mesophilic, total coliforms, Vibrio spp., Escherichia coli and Salmonella) of the bivalve was evaluated monthly, as well as the environmental parameters (temperature, salinity, dissolved solids and pH) in the waters of the bank. The annual averages obtained in oyster meat for mesophilic aerobes were 4.76 × 105 CFU/g, total coliforms 1.15 × 103 CFU/g, and vibrios 0.61 × 104 CFU/g. Apart from this, there was the presence of Escherichia coli in the first months of 2019 with values up to 7.70 x 102 CFU/g, and the presence of Salmonella in 25% of the samples in the months of March, April and June 2019. Many of the values exceed international regulations and reflect a high risk to public health when consuming this mollusk without having previously undergone a purification or process that reduces the bacterial load. The results show a high variability of values during the year, which produces significant differences between months. Aerobic mesophiles and Vibrio spp. show the existence of a strong positive association with temperature, while coliforms (including Echericha coli) exhibit a negative association with salinity and dissolved solids, which suggests a relationship with the rainy season, with greater discharge and dragging of pollutants.