[Design of means for counting allochtonous pathogenic bacteria from natural water]

Allochthonous microorganisms of aquatic ecosystems are not well adapted to survive, grow and reproduce in these environments, because of the lack of nutrients and the negative influence of environmental biotic and abiotic factors exerted on them. These factors produce a stress or sublethal injury on the allochthonous bacteria, which causes their inability to grow on the selective media routinely used for their detection and enumeration. Therefore, the methods used for the analysis of the sanitary water quality must allow the recovery of the physiological injured cells. In the present study, we have evaluated the efficiency of a new recovery medium of Staphylococcus aureus from water samples in comparison with other selective media previously formulated. The efficiency studies consider a series of parameters, such as accuracy, selectivity, specificity, reliability and precision.