Relationships between Legionella and Aeromonas spp. and associated lake bacterial communities across seasonal changes in an anthropogenic eutrophication gradient.

Anthropogenic eutrophication of lakes threatens their homeostasis and carries an increased risk of development of potentially pathogenic microorganisms. In this paper we show how eutrophication affects seasonal changes in the taxonomic structure of bacterioplankton and whether these changes are associated with the relative abundance of pathogenic bacteria of the genera Legionella and Aeromonas. The subject of the study was a unique system of interconnected lakes in northern Poland (Great Masurian Lakes system), characterized by the presence of eutrophic gradient. We found that the taxonomic structure of the bacterial community in eutrophic lakes was significantly season dependent. No such significant seasonal changes were observed in meso-eutrophic lakes. We found that there is a specific taxonomic composition of bacteria associated with the occurrence of Legionella spp. The highest positive significant correlations were found for families Pirellulaceae, Mycobacteriaceae and Gemmataceae. The highest negative correlations were found for the families Sporichthyaceae, Flavobacteriaceae, the uncultured families of class Verrucomicrobia and Chitinophagaceae. We used also an Automatic Neural Network model to estimate the relative abundance of Legionella spp. based on the relative abundance of dominant bacterial families. In the case of Aeromonas spp. we did not find a clear relationship with bacterial communities inhabiting lakes of different trophic state. Our research has shown that anthropogenic eutrophication causes significant changes in the taxonomic composition of lake bacteria and contributes to an increase in the proportion of potentially pathogenic Legionella spp.

Comparison of Yersinia enterocolitica DNA Isolation from Swabs Without Pre-Enrichment on Selective Media With Isolation Preceded by Warm and Cold Enrichment.

Bacteriological methods for the identification of Yersinia enterocolitica are laborious and time-consuming. The aim of this study was to compare Y. enterocolitica DNA isolation from swabs without pre-enrichment on selective media with isolation preceded by warm and cold enrichment. The material for the study consisted of 150 rectal swabs taken from 50 clinically healthy fattening pigs. Forty-one Y. enterocolitica strains were isolated after warm enrichment and 43 after cold enrichment. The presence of ail, ystA, and yadA gene fragments was detected in all isolates. DNA isolation from swabs without pre-enrichment supported the detection of Y. enterocolitica in only nine samples. This study demonstrates that Y. enterocolitica DNA can be isolated from swabs without pre-enrichment on selective media, but this method is less sensitive than the approach where DNA isolation is preceded by warm or cold enrichment.