Evaluation of recovery methods to detect faecal streptococci in polluted waters

Aims: This paper compares the faecal streptococci count on 25 samples of po lluted waters obtained with three techniques: most probable number (MPN), m embrane filtration (MF) and pour plate (PP) methods. Although the YP method is a simple technique, familiar to water bacteriologists, it is not recomm ended in the international methods. Methods and Results: For the MPN method, azide dextrose broth and ethyl vio let azide broth were employed. For the MF technique, Millipore filters were placed onto azide maltose agar (KF agar), while for the PP method, 1 ml of a decimal water dilution was added to (Kennel Faecal) KF medium. Regressio n analysis and Friedman's ANOVA were performed to determine the relationshi p between faecal streptococci counts obtained with the three techniques. St atistical analysis of the results showed that the MPN, MF and PP techniques were equally valid with respect to faecal streptococci enumeration in poll uted waters. Conclusions: Since the PP method was found to be as good as the other techn iques, it may be preferred in polluted waters. It is more economical in ter ms of both time and materials than the MPN count, and it is as accurate as the MF count. Significance and Impact of the Study: This study indicates that the PP meth od, although not recommended internationally, is a reliable alternative to MF and MPN.