Abstract

DIAZ PEREZ, Marilyn et al. Quantitative determination of enterococci in water using an alternative chromogenic method. Rev Cubana Invest Bioméd [online]. 2014, vol.33, n.1, pp.1-11. ISSN 0864-0300.

Introduction: water quality control is essential for the protection of human health and biodiversity in the aquatic environment. For this purpose, several microorganisms are used as indicators of fecal contamination. Among them are enterococci, which are considered to be good indicators, since they survive for a longer time in adverse natural conditions. Objectives: evaluate the suitability of a new alternative chromogenic method for the detection and enumeration of enterococci in water by membrane filtration technique, in comparison with the ISO 7899:2 standard method. Methods: water samples were collected from three different sources to determine their quality. The samples were assayed in parallel with the two methodologies (alternative and reference) using the membrane filtration technique. The following parameters were determined to evaluate the performance of the methods: sensitivity, specificity, accuracy, percentage of false positives, percentage of false negatives, kappa index. The first three parameters were estimated for both methods before and after confirmation by biochemical testing. Results were analyzed statistically based on the main criteria defined by ISO standards 16140 and 177994. Results: with the alternative method, results were obtained at 24 h, whereas the reference method required more than 48 h. Sensitivity and accuracy were higher with the alternative method (99 % and 98 %, respectively) than with the reference method (97% and 97%, respectively). Both methods had similar efficiency and accuracy, with almost perfect concordance between them (kappa = 0.96) in all the water samples tested. Conclusions: results show that the alternative method is efficient for the enumeration of enterococci from different types of water samples. It is also a simple, faster and economically feasible method.

Keywords : enterococci; glucosidase; alternative method; water.

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