## 3 Results
### Quantitative Analysis of Antibiotic Resistance Genes and Taxonomic Genes  
2.1 Quantitative Pccurrence of Antibiotic Resistance Genes among the Total Number of Antibiotic-Resistant Bacteria  
Among the analysed DNA samples of bacterial populations from the TSA universal culture medium, the presence of all the tested genes responsible for the resistance to beta-lactam antibiotics and tetracyclines was detected, with the exception of four wastewater treatment plants (No. VII, VIII, XI, X), in which the _bla_OXA gene was not detected (Figure 1). The genes occurring at the highest average concentrations were _tet_A (from 8.72 \(\times\) 10\({}^{-4}\) to 1.07 gene copies/gene copies 16S _r_RNA) as well as _bla_OXA (from 8.54 \(\times\) 10\({}^{-3}\) to 4.53 \(\times\) 10\({}^{-1}\) gene copies/16S _r_RNA gene copies) and _bla_TEM (from 8.33 \(\times\) 10\({}^{-4}\) to 1.49 \(\times\) 10\({}^{-1}\) gene copies/16S _r_RNA gene copies). The other genes responsible for antibiotic resistance occurred at a similar level, at concentrations of the order of 1 \(\times\) 10\({}^{-3}\)-1 \(\times\) 10\({}^{-2}\) gene copies/16S _r_RNA gene copies. An analysis of the correlations between concentrations of particular genes originating from the total bacterial population revealed a statistically significant correlation between the _bla_SHV gene and all antibiotic resistance genes. Moreover, there was also a positive correlation between _bla_OXA and _tet_M, and between _bla_TEM and _tet_A genes (Table 1). An analysis of the correlation between the concentration of particular genes and the count of microorganisms demonstrated a statistically significant correlation between the concentration of the _bla_SHV gene in the DNA of the total bacterial population and the microorganism count on TSA media, both with and without the supplementation with the tested antibiotics. However, no significant correlation was found between physicochemical parameters and the concentration of genes, or between HRT values of the analysed treatment plants and the concentration of genes in wastewater. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c} \hline \hline  & & \multicolumn{10}{c}{Spearman’s Rank Coefficient} \\ \cline{2-13}  & **TS/A** & **TSA-AMO** & **TSA-CTV** & **TSA-OX** & **TSA-DOX** & _tet_A** & _tet_M** & _bla_TEM** & _bla_OXA & _bla_SHV & _nit_A & **HRT** & **TSS** & **BOD** \\ \hline TSA- & & & & & & & & & & & & & \\ AMO/1 & **0.95** & & & & & & & & & & & & \\ \multicolumn{13}{c  
Following the wastewater treatment process, the average concentration of genes that are responsible for the resistance to beta-lactams and tetracyclines decreased at levels ranging from 0 to 100% (Table 2). A reduction in the concentration of all antibiotic resistance genes under study was observed in the DNA of the total bacterial population from WWTP No. VI, group B (mechanical and biological treatment plants), and WWTP No. XIII, group D (increased nutrient removal mechanical and biological treatment plants). Moreover, in the DNA of the total bacterial population from other group D WWTPs, an increase was observed in the concentration of one gene in treated wastewater, i.e., _tet_M in WWTP No. XII and _bla_SHY in WWTP No. XI. Only in the DNA of the bacterial population from WWTP no. III, group B, was an increase noted in the concentrations of all the tested genes following the wastewater treatment process. However, in the DNA of the total bacterial population from WWTPS no. IV and V  
Figure 1: Relative antibiotic resistance gene (ARG) concentration in total bacteria population: (**a**) _tet_A (**b**) _tet_M (**c**) _bla_TEM (**d**) _bla_OXA (**e**) _bla_SHY (**f**) _uid_A in collected wastewater samples. An asterisk (*) denotes a statistically significant difference (ANOVA; \(p<0.05\)) between wastewater treatment plant (WWTP) untreated and treated samples. I-XIII–denote numbers of WWTPs. Group A (I, II), group B (III–VII), group C (VIII–X), group D (XI–XIII); a—untreated wastewater, b—treated wastewater.