Abstract
BackgroundThe present study aims the characterization of antibiotic resistance phenotypes and encoding genes in bacterial strains isolated from some Romanian aquatic fishery lowland salted lakes. Material/MethodsThis study was conducted on 44 bacterial strains, mainly belonging to species used as microbiological indicators of fecal pollution isolated from four natural fishery lakes. All strains were tested for their antibiotic susceptibility by disk diffusion method. Simplex and multiplex PCR were performed to identify the β-lactams antibiotic resistance genes (blaNMD, blaOXA−48, blaVIM, blaIMP, blaCTX−M, blaTEM), sulfonamides (Sul1, Sul2), tetracyclines (TetA, TetB, TetC, TetD, TetM), aminoglycosides (aac3Ia), vancomycin (VanA, VanB, VanC), macrolides (ermA, ermB, ermC) as well as the plasmid-mediated quinolone resistance (PMQR) markers (QnrA, QnrB, QnrS), and class 1 integrons (Int1, drfA1-aadA1).ResultsThe Enterococcus spp. isolates exhibited phenotypic resistance to vancomycin (35 %) and macrolides (erythromycin) (75 %); from the vancomycin – resistant strains, 5 % harboured VanA (E. faecalis), while the erythromycin resistant isolates were positive for the ermA gene (E. faecalis − 10 %, E. faecium − 5 %). The Gram- negative rods (GNR) exhibited a high level of resistance to β-lactams: cefuroxime (63 %), cefazolin (42 %), ceftriaxone (8 %), ceftazidime and aztreonam (4 % each). The genetic determinants for beta-lactam resistance were represented by blaCTX−M−like (33 %), blaNDM−like and blaIMP−like (8.33 %) genes. The resistance to non-β-lactam antibiotics was ascertained to the following genes: quinolones (QnrS − 4.16 %); sulfonamides (Sul1–75 %, Sul2–4.16 %); aminoglycosides (aac3Ia − 4.16 %); tetracyclines (tetA – 25 %, tetC − 15 %). The integrase gene was found in more than 50 % of the studied strains (58.33 %).ConclusionsThe cultivable aquatic microbiota from fishery lakes is dominated by enterococci and Enterobacterales strains. The GNR strains exhibited high levels of β-lactam resistance mediated by extended spectrum beta-lactamases and metallo-β-lactamases. The Enterococcus sp. isolates were highly resistant to macrolides and vancomycin. The high level and diversity of resistance markers, correlated with a high frequency of integrons is suggesting that this environment could act as an important reservoir of antibiotic resistance genes with a great probability to be horizontally transmitted to other associated species from the aquatic sediments microbiota, raising the potential zoonotic risk for fish consumers.
Highlights
The present study aims the characterization of antibiotic resistance phenotypes and encoding genes in bacterial strains isolated from some Romanian aquatic fishery lowland salted lakes.Material/Methods: This study was conducted on 44 bacterial strains, mainly belonging to species used as microbiological indicators of fecal pollution isolated from four natural fishery lakes
The Enterococcus spp. isolates exhibited phenotypic resistance to vancomycin (35 %) and macrolides (75 %); from the vancomycin – resistant strains, 5 % harboured VanA (E. faecalis), while the erythromycin resistant isolates were positive for the ermA gene (E. faecalis − 10 %, E. faecium − 5 %)
The Enterococcus sp. isolates were highly resistant to macrolides and vancomycin
Summary
The present study aims the characterization of antibiotic resistance phenotypes and encoding genes in bacterial strains isolated from some Romanian aquatic fishery lowland salted lakes.Material/Methods: This study was conducted on 44 bacterial strains, mainly belonging to species used as microbiological indicators of fecal pollution isolated from four natural fishery lakes. As antibiotics are one of the most popular pharmaceuticals used in medicine, veterinary care, and farming [9, 10], they can be released, most of them unchanged, into the environment. They appear as contaminants of the water bodies, especially those frequently impacted by anthropogenic activities (e.g., wastewater, municipal sewage, influents and effluents of wastewater treatment plants) [11], which have been suggested to be ideal reservoirs and vectors for the AR origin, evolution and spread [12,13,14]. Lakes, rivers or streams, bacteria from different sources, probably selected by intensive antibiotic usage, are collected and mixed with environmental strains, which on their turn, could introduce the newly acquired antibiotic resistance genes (ARGs) into the clinics [15,16,17]
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