OBJECTIVES: Urban wastewater contains various micropollutants and a high number of different micro-organisms. Some bacteria in wastewater can attach to surfaces and form biofilm, which gives bacteria an advantage in the fight against environmental stresses. This work focused on analysis of bacterial communities in biofilms isolated from influent and effluent sewerage of a wastewater treatment plant (WWTP) in Bratislava, Slovakia. METHODS: Detection of biofilm microbiota was performed by culture-independent and -dependent approaches. The composition of bacterial strains was detected by denaturing gradient gel electrophoresis fingerprinting coupled with construction of 16S rRNA clone libraries. Analysis of the concentration of antibiotics and the prevalence of antibiotic-resistant coliforms, Enterococcus spp. and Staphylococcus spp. in sewerage was also studied. RESULTS: Biofilm collected at the inlet point was characterised primarily by the presence of Pseudomonas spp., Acinetobacter spp. and Janthinobacterium spp. clones, whilst members of the genus Pseudomonas were largely detected in biofilm isolated in outflow of the WWTP. Predominant antibiotics such as azithromycin, clarithromycin and ciprofloxacin were found in influent wastewater. The removal efficiency of these antibiotics, notably azithromycin and clarithromycin, was 30% in most cases. CONCLUSION: The highest number of antibiotic-resistant bacteria, with a predominance of coliforms, was detected in samples of effluent biofilm. Multidrug-resistant strains in effluent biofilm showed very good biofilm-forming ability.

Department of Environmental Engineering Faculty of Chemical and Food Technology Slovak University of Technology Radlinského 9 812 37 Bratislava Slovakia

Department of Nutrition and Food Quality Assessment Faculty of Chemical and Food Technology Slovak University of Technology Radlinského 9 812 37 Bratislava Slovakia

Institute of Biochemistry and Microbiology Slovak University of Technology Radlinského 9 812 37 Bratislava Slovakia

Institute of Molecular Biology Slovak Academy of Science Bratislava Dúbravská cesta 5777 21 845 51 Karlova Ves Slovakia

University of South Bohemia in Ceske Budejovice Faculty of Fisheries and Protection of Waters South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses Zátiší 728 2 389 25 Vodňany Czech Republic

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Hospital Wastewater-Important Source of Multidrug Resistant Coliform Bacteria with ESBL-Production