## 3 Results and Discussion
The results of the study on Great Rudnickie Lake allow us to expand our knowledge in this area when it comes to recreational waters in Central Europe. It should also be pointed out that bathing water users can be a source of resistant microflora, which can then spread via water to other users of the water reservoir. The higher the concentration of this antibiotic-resistant bacteria, the greater the likelihood that this particular bacteria will be transmitted. As for local residents, the use of the reservoir water to irrigate nearby fields may also become a source of the spread of antibiotic resistance in proportion to the scale of occurrence of these factors in the water. Our study revealed that mesophilic bacteria resistant to ciprofloxacin and imipenem were present in the samples collected at all sampling points, including those taken directly from the bathing areas heavily frequented by tourists. The average number of ciprofloxacin-resistant bacteria ranged from 201 to 1490 CFU/cm\({}^{3}\) (584 \(\pm\) 453 CFU/cm\({}^{3}\) for all the samples), and it was quite similar in the waters flowing into the lake and in samples collected from the bathing area located on the east side of the Great Rudnickie Lake. The ciprofloxacin-resistant bacteria in inflowing Marusha river waters and water samples from bathing areas accounted for from 3% to 7.3% of the total number of mesophilic bacteria. What was surprising, however, was that the percentage of these bacteria was four times higher in the waters flowing out of the lake, reaching 28% of the total bacterial count. The number of impenem-resistant bacteria was at the level of 89-190 CFU/cm\({}^{3}\), with an average value of 145 \(\pm\) 44 CFU/cm\({}^{3}\) of tested water. Similarly to the ciprofloxacin-resistant bacteria, the highest number and percentage of impenem-resistant bacteria was detected in waters flowing out of the lake, reaching 3.6% of the total number of mesophilic bacteria, which was almost twice as high as in waters flowing into the lake. The average percentage of impenem-resistant bacteria in bathing areas was also lower compared to the waters inflowing to the Rudniczanka River (Figure 1). Of the 42 pure bacterial isolates obtained, 25 were resistant to ciprofloxacin but sensitive to impenem; six showed resistance to impenem but sensitivity to ciprofloxacin, while 11 strains were resistant to both antibiotics tested. Analysis of genes determining mechanisms of antibiotic resistance is a useful tool in the study of this phenomenon. In this research, two antibiotic-resistance genes were considered: _bla_TEM and _qnr_S. The _bla_TEM gene encodes TEM-1 \(\beta\)-lactamase typical for _Enterobacteriaceae_[42]. \(\beta\)-lactamases are originally encoded by the genes located on bacterial nucleoid, although they can also be found on plasmids and mobile elements like transposons and integrons [42; 43]. The TEM enzymes are the representatives of fast-evolving extended spectrum \(\beta\)-lactamases [44]. The _qnr_S gene is one of the genes responsible for the resistance against fluoroquinolone antibiotics (including ciprofloxacin). The gene has been primarily found in _Enterobacteriaceae_. It was revealed that it can be spread by IncU-type plasmids [45; 46]. The analysis of the occurrence of _bla_TEM and _qnr_S in 42 antibiotic-resistant isolates from the Great Rudnickie Lake revealed the presence of the _bla_TEM gene in 100% of impenem-resistant strains (Figure 2), while the _qnr_S was present only in 17-40% of ciprofloxacin-resistant bacteria which suggests that different determinants of antibiotic resistance should be seen in the case of ciprofloxacin. The presence of genes that usually co-occur with mobile genetic elements may explain the prevalence of certain antibiotic-resistance mechanisms and implies the possibility of spreading antibiotic-resistance in studied recreational areas and its transfer into the other microorganisms, including potentially pathogenic microflora.