## 4 Discussion
Pathogenic strains belong to groups B\({}_{2}\) and D, whereas the commensal microbiota consists of groups A and B\({}_{1}\). _E. coli_ isolates from broiler chicken cloacal swabs and meat samples were analyzed and classified into all four phylogenetic groups. A and B\({}_{1}\) were the groups that dominated, followed by D and B\({}_{2}\). _E. coli_ commensal strains frequently exhibit multidrug resistance. In the context of One Health, their share increases annually, and adds to the growing antimicrobial resistance [58]. Several studies confirm that food-producing animals, including poultry, are reservoirs of _E. coli_ and _Klebsiella_ spp., which are producers of EBLs. Nowadays, not only EBL genes, but also other antimicrobial resistance genes, mainly _qnr_ and _tet_ genes, are increasingly being detected [48; 59]. The _qnr_ABS genes encode proteins that protect _E. coli_ DNA gyrase from inhibition by quinolone, even at low drug concentrations [59]. Our research has revealed that most strains with _qnr_ genes present did not have phenotypic resistance to ciprofloxacin. In _E. coli_ isolates, the _qnr_B gene was present in only one isolate, whereas the _qnr_A (26.5%) and _qnr_S (14.7%) genes were more frequently present. In one isolate, both _qnr_A and _qnr_B genes were present. Our findings are consistent with those of [PERSON] et al. [60], who detected _qnr_A (61.6%), _qnr_B (7.7%), and _qnr_S (23.0%) genes in APEC isolates. However, [PERSON] et al. [61] found _aac(6')-lb-cr_, _qnr_A, and _qnr_B in addition to a 15.1% abundance of _qnr_S. Similar to this, in avian pathogenic _E. coli_ isolates, [PERSON] and [PERSON] [62] discovered all four genes: _qnr_S (9.4%), _qnr_A (6.6%), _qnr_B (3.8%), and _aac(6')-lb-cr_ (1.9%). [PERSON] et al. [63] reported that _qnr_ABS-positive plasmids often contain genes that also encode resistance to \(\beta\)-lactams, tetracyclines, sulfonamides, trimethoprim, aminoglycosoides, chloramphenicol, and rifampicin. _E. coli_'s resistance to tetracycline involves an efflux mechanism, which is controlled by as many as nine genes--_tet_A, _tet_B, _tet_C, _tet_D, _tet_E, _tet_G, _tet_J, _tet_L, and _tet_Y. [15; 60]. Our research focused on the detection of _tet_A and _tet_B genes, which are among the most commonly found _tet_ genes in _Enterobacteriaceae_ bacteria. [PERSON] et al. [48] found that _tet_A was the most abundant gene in _E. coli_ obtained from chicken samples, similar to our study. [PERSON] et al. [64] also reported that the _tet_A gene was the most prevalent tetracycline resistance gene (71.1% of isolates), followed by _tet_B (18.4%), in poultry in Vietnam. The most prevalent _tet_B gene was found in avian pathogenic _E. coli_ isolated from broiler, layer, and breeder chickens in Nepal [65]. The present study confirms the increasing prevalence of _tet_ and _qnr_ genetic determinants among _E. coli_ isolates of avian origin. According to [PERSON] et al. [66] and [PERSON] et al. [67], their widespread distribution among bacterial populations is due to the association of _tet_ or _qnr_ genes with mobile genetic elements. Mobile genetic elements (MGEs) are often involved in horizontal gene transfer (HGT) processes in bacteria, and facilitate their rapid evolution and adaptation. [PERSON] et al. [68] found an increased abundance of MGEs (_Int1_ and _Tn3_) in broiler chicken samples, which is compatible with our findings. We detected the class 1 integrin cassette (_Int1_) in more than half of the _E. coli_ strains. The majority of the isolates studied had _Tn3_ transposon genes. The presence of both _Int1_ and _Tn3_ genes simultaneously was found in 52.9% of _E. coli_ isolates. _E. coli_ strains of avian origin may contain various virulence factors such as adhesins, invasins, toxins, iron uptake systems, and protectins that highlight their zoonotic potential [69]. In our study, we also confirmed the presence of four of the five tested genes associated with virulence in isolates of avian _E. coli_, namely, _fim_A (97.1%), _iut_A (76.5%), _cou_C (38.2%), and _kpsMT_ II (8.8%).