# Antibiotic Resistance in the Farming Environment
## 3 Farmed Animals as Reservoirs of Antibiotic Resistance
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Type of Livestock** & **Bacteria under Study** & **Resistance Level** & **Antibiotics** & **Detected Genes** & **References** \\ \hline Poultry & _E. coli_ & 47.4\% & Nalididic acid & & [41] \\ Poultry & _E. coli_ & \textgreater{}10\% & Cefotaxim & & [41] \\ Poultry & _E. coli_ & \textgreater{}50\% & Sulfisoxazole, streptomycin & & [41] \\ Poultry & _E. coli_ & \textgreater{}40 & Tetracycline, gentamicin & & [41] \\  & & & Trimethoprim/sulfamethoxazol, tetracycline, chloramphenicol, amoxicillin/clavulanic acid & qnrS & \\ Poultry & _Enterobacteriaceae_ & 60–70\% & tetracycline, chloramphenicol, amoxicillin/clavulanic acid & different tet genes & [42] \\  & & & Penicillin, ciprofloxacin, rifáampicin, kanamycin, & & \\ Poultry & Different isolates & \textgreater{}50\% & streptomycin, erdiximab, erythromycin, ampicillin, Tetracycline & & [43] \\  & & & Tetracyclinelin & & \\ Sheep & _Staphylococcus aureus_ & 23.5\% & Methicillin, multi-resistant & & [44] \\ Cattle & _E. coli_ & 24.5–30.6\% & Ampicillin, streptomycin & & [41] \\  & & & Sulfonamide, tetracycline & & \\ Cattle and goats & _Staphylococcus aureus_ & 17.6\% & Methicillin, multi-resistant & & [44] \\  & _E. coli_ & Significant resistance & Azithromycin, tetracycline, erythromycin, oxytetracycline, erA & & [45] \\ Cattle & _Salmonella_ sp. & 14.2–79.2\% & Tetracycline & & [46] \\ Cattle & _E. coli_ & & & cfrB & [47] \\  & & & & optrA & \\ Swine & _Enterobacteriaceae_ & 80–90\% & Tetracycline, trimethoprim/sulfamethoxazol & & [42] \\  & & & Nalidix acid, erythromycin, etcracycline, spr. & tetO & \\ Swine & _Campylobacter_ & 35.5–79.6 & tetracycline, azithromycin, citr & & \\  & & & Ciprofloxacinacin & & \\ Swine & _E. coli_ & 70\% & Tetracycline, streptomycin, & & [49] \\ Swine & _Enterococcus faecalis_ & 70–100\% & Streptomycin, tetracycline & & [50] \\ Swine & _Enterococcusecium_ & Up to 97\% & Ampicillin, oxytetracycline, gentamicin, streptomycin & & [50] \\ \hline \hline \end{tabular}
\end{table} 
Table 2: _Cont._their relative abundance was comparable to that observed on typical industrial farms. Also, a study conducted by [PERSON] et al. [53] on poultry farms in Italy showed the presence of antibiotic resistance genes both at antibiotic-using and non-antibiotic broiler farms. There is evidence that there may be a number of bacteria in the digestive tract of animals that exhibit natural antibiotic resistance, unrelated to the pressure caused by antibiotic use [54]. Colonization of livestock organisms by antibiotic-resistant bacteria may result not only from their selection in the presence of antibiotics used as feed additives but also from contact with drug-resistant microflora present in the environment, such as during grazing [18]. This could suggest that even abandoning the use of antibiotics in animal husbandry may not be enough to limit the spread of drug resistance in a farming environment. However, the relationship between the composition and structure of the intestinal microflora of cattle, pigs, and poultry and the drug resistance profile of the microorganisms can be observed [45; 55]. There are some data suggesting that one of the determinants of the antibiotic resistance phenomenon in the farming environment is the breeding practices used (Figure 2). Intensive animal husbandry involves the accumulation of a large number of individuals in a relatively small space, which increases the likelihood of the spread of infectious diseases, thus providing an argument for the use of antibiotics for prophylactic purposes. This is of particular importance, especially in large-scale poultry farming [1; 35]. Meanwhile, a study conducted in Ecuador confirmed that the phenomenon of bacterial antibiotic resistance was more prevalent in poultry raised in an industrial system compared to domestic conditions (resistance to tetracycline 78% and 34%, respectively, to sulfisoxazole 69% and 20%, respectively, while to trimethoprim/sulfamethoxazole it was 63 and 17%, respectively) [56].