Comparison of the Legiolert™/Quanti-Tray® MPN test for the enumeration of Legionella pneumophila from potable water samples with the German regulatory requirements methods ISO 11731-2 and ISO 11731.

Due to the promising results of a previous study of the performance of the novel MPN method (Legiolert™/Quanti-Tray®) compared to ISO 11731-2, this study was performed to compare Legiolert for Legionella pneumophila with the German regulatory requirements methods ISO 11731-2 (100 ml membrane filtration) and ISO 11731 (1 ml direct plating) for the enumeration of L. pneumophila and Legionella spp. from potable water. Data from a multi-laboratory study according to ISO 17994 showed that Legiolert yielded on average higher counts of L. pneumophila than the ISO 11731-2 method, but the comparison with ISO 11731 was inconclusive due to the number of samples needing to be tested. Likewise, comparisons of the MPN method for 100 ml to the highest result of either ISO 11731 or ISO 11731-2 according to Federal Environmental Agency recommendation (2012) yielded no conclusive difference, regardless of whether non-pneumophila species of Legionella were included in the evaluation. The MPN method has a high specificity for L. pneumophila of 97.9% which compares favourably to the specificity of 95.3% quoted for ISO 11731. The new method represents a significant improvement in the enumeration of L. pneumophila from drinking water and related samples.

Temporal and spatial distribution patterns of potentially pathogenic Vibrio spp. at recreational beaches of the German north sea.

The number of reported Vibrio-related wound infections associated with recreational bathing in Northern Europe has increased within the last decades. In order to study the health risk from potentially pathogenic Vibrio spp. in the central Wadden Sea, the seasonal and spatial distribution of Vibrio vulnificus, Vibrio parahaemolyticus, Vibrio alginolyticus and Vibrio cholerae were investigated at ten recreational beaches in this area over a 2-year period. V. alginolyticus and V. parahaemolyticus were found to be omnipresent all year round in the study area, while V. vulnificus occurrence was restricted to summer months in the estuaries of the rivers Ems and Weser. Multiple linear regression models revealed that water temperature is the most important determinant of Vibrio spp. occurrence in the area. Differentiated regression models showed a species-specific response to water temperature and revealed a particularly strong effect of even minor temperature increases on the probability of detecting V. vulnificus in summer. In sediments, Vibrio spp. concentrations were up to three orders of magnitude higher than in water. Also, V. alginolyticus and V. parahaemolyticus were found to be less susceptible towards winter temperatures in the benthic environment than in the water, indicating an important role of sediments for Vibrio ecology. While only a very small percentage of tested V. parahaemolyticus proved to be potentially pathogenic, the presence of V. vulnificus during the summer months should be regarded with care.