## 3 Results and Discussion
In both seasons, _qep_A was not detected in river water sampled upstream from the effluent discharge point, but it was identified in the samples collected downstream from the effluent discharge point. According to the literature, _aac(6')-lb-cr_ and _qepA_ genes are commonly found in the wastewater. [PERSON] and [PERSON] [21] detected both genes in influents and effluents from 13 wastewater treatment plants with different type of the wastewater treatment technologies modifications. [PERSON] et al. [61] found _aac(6')-lb-cr_ and _qep_A in treated wastewater from three Chinese hospitals, in municipal wastewater and in river water. In each sampling site, the _aac(6')-lb-cr_ gene had higher copy numbers than the _qep_A gene. [PERSON] et al. [48] analyzed samples of unpolluted river water and samples of river water collected in the vicinity of hospitals. The _qep_A gene was not detected in any of the samples, whereas the _aac(6')-lb-cr_ gene was ubiquitous in all samples. The lower prevalence of _qep_A could be attributed to the fact that resistance to fluoroquinolones encoded by this gene evolved relatively late. The _qep_A gene was first identified in 2007 by research teams from Belgium and Japan [62; 63]. The first mechanism of plasmid encoded resistance to fluoroquinolones was discovered in 1998 [64]. It should be noted that all studied genes (excluding _qep_A at site W7 in fall) were present in treated sewage sludge intended for further use. More than 500,000 tons of sewage sludge are produced each year in Poland, of which around 20% are used as agricultural fertilizers on account of their high organic matter content [65]. The application of sewage sludge as agricultural fertilizer contributes to the spread of antibiotic resistance in the environment [28]. [PERSON] et al. [28] found that sewage sludge fertilization can transfer up to 108 of ARGs and MGEs to soil. The resulting increase in bacterial diversity in the soil environment was significantly correlated with the prevalence of ARGs. Sewage sludge is particularly abundant in tetracycline and sulfonamide resistance genes [27]. According to [PERSON] et al. [27], sulfonamide resistance genes (_su1_1 and _su1_2) were the most frequently occurring ARGs (45.6%) in the examined sewage sludge. The number of _su1_ copies in sewage sludge significantly exceeded (26-87 times) the number of _su2_ copies. [PERSON] et al. [27] also observed that the prevalence of sulfonamide resistance genes was six-fold (%) higher in sewage sludge than in raw wastewater, which suggests that these genes are highly accumulated in sewage sludge. Quinolone resistance genes were identified significantly less frequently, and they were not present in sewage sludge. The accumulation of ARGs and MGEs in soil could imply that the application of sewage sludge could accelerate gene transmission to the soil environment via HGT. The presence of antibiotics acting as active mutagens can also significantly contribute to the evolution of drug resistance mechanisms. Sublethal concentrations of antibiotics, which are frequently noted in wastewater, can lead to mutations that promote the emergence of drug resistance [66; 67]. The samples of raw sewage, treated wastewater and river water that were examined in the current study were additionally analyzed by [PERSON] et al. [68] for the presence of 26 antimicrobials. Very high concentrations of sulfamethoxazole (SXT) and ciprofloxacin (CIP) were noted in raw wastewater reaching both WWTPs, and they were nearly three times higher in WM-WWTP than in S-WWTP. It should also be noted that CIP levels in raw wastewater exceeded the minimum inhibitory concentrations (MIC) recommended by EUCAST for most microorganisms [69]. To regulate the risk issuing from the concentrations of antibiotics in the environment, [PERSON] and [PERSON] [70] estimated Predicted No-Effect Concentrations (PENCs) of antimicrobials for resistance selection.