## 3 Results
### Quantitative Analysis of Antibiotic Resistance Genes and Taxonomic Genes
#### 3.2.2 Quantitative Occurrence of Antibiotic Resistance Genes among Antibiotic-Resistant _E. coli_  
In the DNA of the bacterial population from _E. coli_ selective medium mFc, _tet_M, _tet_A, and _bla\({}_{\text{OXA}}\)_ genes were not detected in untreated wastewater from all treatment plants (Figure 2).  
Following the wastewater treatment process, the average concentration of genes that are responsible for the resistance to beta-lactams and tetracyclines decreased at a level ranging from 0 to 100% (Table 4).  
A complete reduction in genes was observed for the _tet_A gene in the DNA of _E. coli_ population from four wastewater treatment plants (No. VII, VIII, X, XI) and for the _bla\({}_{\text{OXA}}\)_ gene for the DNA of _E. coli_ population isolated from WWTP No. III. A reduction in all genes under study was observed only in the DNA of _E. coli_ populations from WWTPs No. VIII and IX, group C, ranging from 21% to 100%. An increase in the concentration of all genes under study following the wastewater treatment process was observed in the DNA of _E. coli_ population from WWTP No. IV, group B. In addition, an increase in the concentrations of four genes under study (_tet_A, _tet_M, _bla\({}_{\text{OXA}}\)_, _bla\({}_{\text{TEM}}\)_) was also observed in the DNA of _E. coli_ population in WWTP No. V, group B, and gene _bla\({}_{\text{SHV}}\)_ was reduced only by 8%. Wastewater treatment plants reduced the concentration of the _bla\({}_{\text{OXA}}\)_ gene most efficiently. However, the _bla\({}_{\text{TEM}}\)_ gene, whose concentration increased following the treatment process, was noted in the  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline
**Sewage Treatment Technology** & **Treatment** & _tet_A & _tet_M & _bla\({}_{\text{TEM}}\)_ & _bla\({}_{\text{OXA}}\)_ & _bla\({}_{\text{SHV}}\)_ & _uid_A \\ \cline{2-8}
**Used** & I & * & 56.66 & * & * & 36.97 & * \\ \hline \multirow{3}{*}{A. WWTPs with A\({}_{2}\)O system} & II & 99.88 & 83.58 & * & 100 & 100 & * \\ \cline{2-8}  & III & * & * & * & * & * & * \\ \cline{2-8}  & IV & * & * & 96.73 & * & * & 1.21 \\ \cline{2-8}  & V & * & * & 42.45 & * & * & 7.97 \\ \cline{2-8}  & VI & 99.87 & 94.27 & 93.90 & 100 & 97.05 & 31.93 \\ \cline{2-8}  & VII & * & 93.87 & * & ** & * & 49.51 \\ \hline \multirow{3}{*}{C. WWTPs with Sequencing Batch Reactors (SBR)} & VIII & 87.89 & * & 46.94 & ** & 100 & * \\ \cline{2-8}  & IX & * & 99.98 & * & 100 & 90.66 & * \\ \cline{2-8}  & X & 94.46 & * & 25.24 & ** & 58.49 & 23.50 \\ \hline D. WWTPs with mechanical-biological system with elevated removal of nutrients & XI & 70.34 & 13.17 & 81.96 & ** & * & 19.44 \\ \cline{2-8}  & XII & 98.68 & * & 95.82 & 47.98 & 100 & 72.85 \\ \cline{2-8}  & XIII & 87.16 & 91.55 & 88.59 & 98.78 & 88.34 & 79.56 \\ \hline \end{tabular}  
*—increase in gene concentration, **——no gene presence, WWTP— wastewater treatment plant.  
\end{table}
Table 2: Gene concentration reduction in total bacteria population.  
DNA of the population of _E. coli_ from as many as eight WWTPs and was the most difficult to remove from wastewater.  
Figure 2: Relative ARGs concentration in _E. coli_ population: (**a**) _tet_A (**b**) _tet_M (**c**) _bla_TEM (**d**) _bla_OXA (**e**) _bla_SHV (**f**) _uid_A in collected wastewater samples. An asterisk (*) denotes a statistically significant difference (ANOVA; \(p\) < 0.05) between WWTP influent and effluent samples. I-XIII—denote number of WWTPs. Group A (I, II), group B (III–VII), group C (VIII–X), group D (XI–XIII); a—untreated wastewater, b—treated wastewater.