Prediction of Salmonella in seawater by total and faecal coliforms and Enterococci

Abstract

The power of total coliforms (TC), faecal coliforms (FC) and Enterococci to predict the presence of Salmonella in seawater was investigated. Indicator cut-off values with the most satisfactory combination of sensitivity and specificity in predicting Salmonella presence were 1000 CFU 100 ml −1 TC, 200 CFU 100 ml −1 FC, 500 CFU 100 ml −1 Enterococci. When TC or FC were used for Salmonella prediction in logistic regression, then the addition of another indicator did not have a statistically significant effect. When Enterococci were used for prediction, then the addition of either of the two other indicators led to a statistically significant improvement ( P = 0.001 for TC, P = 0.003 for FC). These results suggest that using either TC or FC alone provided an adequate indicator of Salmonella presence, but a statistically significant improvement is possible over using Enterococci alone. Concerning Enterococci, European Union limits for excellent coastal water quality (100 CFU 100 ml −1) and United States Environmental Protection Agency criteria for marine bathing waters (35 CFU 100 ml −1) have the same value in predicting Salmonella absence (92.5%).