In this study, the susceptibility to erythromycin (E) and to trimethoprim/sulfamethoxazole (SXT) among isolates of Enterococcus spp. and Escherichia coli was tested, respectively. Both fecal indicators were detected and isolated from raw (RW) and treated wastewater (TW) as well as from samples of activated sludge (AS) collected in a local wastewater treatment plant (WWTP). Biodiversity of bacterial community in AS was also monitored using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). Additionally, distribution of sul1-3 genes conferring sulfonamide resistance was tested among SXT-resistant E. coli. Simultaneously, basic physicochemical parameters and concentrations of eight antimicrobial compounds (belonging to folate pathway inhibitors and macrolides class) were analyzed in RW and TW samples. Six of the selected antimicrobial agents, namely: erythromycin, clarithromycin, trimethoprim, roxithromycin, sulfamethoxazole, and N-acetyl-sulfamethoxazole were detected in the wastewater samples. Bacterial biodiversity of AS samples were comparable with no relevant differences. Among tested Enterococcus spp., E-resistant isolates constituted 41%. SXT resistance was less prevalent in E. coli with 11% of isolates. The genes conferring resistance to sulfonamides (sul1-3) were detected in SXT-resistant E. coli of wastewater origin with similar frequencies as in other environmental compartments, including clinical ones.
Biological treatment based on activated sludge is effi cient in municipal wastewater treatment. The removal of nitrogen compounds is crucial for sewage purifi cation. Due to the fact that ammonia is toxic for a water environment and causes eutrophication, ammonia oxidation is of the utmost importance in wastewater treatment. Observing the changeability of ammonia oxidizing bacteria (AOB) and identifying their most abundant species can be helpful in the optimization of wastewater treatment. In this study we used denaturing gradient gel electrophoresis (DGGE), combined with cloning and sequencing of 16S rRNA and AmoA gene fragments in order to estimate AOB biodiversity and temporal community changes. Activated sludge samples were collected from the municipal WWTP in Gliwice (Poland) at 2-week intervals. Ammonia concentration in the infl uent during the experiment was 30.2 57.6 mg N-NH 4 + /L. The research revealed a high diversity of uncultured bacteria. It is suspected that these bacteria could be involved in the nitrifi cation, which points to the fact that these bacteria might be effi cient in the process. However such a situation is not confi rmed and it requires further research. The appearance of Ferribacterium-like bacteria together with Nitrosomonas sp. as the most abundant bacteria was found.
Due to the rising use of antibiotics and as a consequence of their concentration in the environment an increasing number of antibiotic resistant bacteria is observed. The phenomenon has a hazardous impact on human and animal life. Sulfamethoxazole is one of the sulfonamides commonly detected in surface waters and soil. The aim of the study was to detect sulfamethoxazole resistance genes in activated sludge biocenosis by use of in situ PCR and/or hybridization. So far no FISH probes for the detection of SMX resistance genes have been described in the literature. We have tested common PCR primers used for SMX resistance genes detection as FISH probes as well as a combination of in situ PCR and FISH. Despite the presence of SMX resistance genes in activated sludge confirmed via traditional PCR, the detection of the genes via microscopic visualization failed.
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