## 2 Materials and Methods
### Antimicrobial Susceptibility Testing and Detection of Extended-Spectrum Beta-Lactamases (ESBL)  
Susceptibility of _E. coli_ strains to the 31 selected antibiotics (listed in Table 1) was assessed on the Mueller-Hinton Agar (Becton Dickinson, Franklin Lakes, NJ, USA) with the Kirby-Bauer disk diffusion method, according to the recommendations of the European Committee on Antimicrobial Susceptibility Testing [20]. _E. coli_ ATCC 25922 was used for quality-control purpose.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Antibiotic**} & \multicolumn{2}{c}{**No. _E. coli_****Subclinical (_n = 109_)} & \multicolumn{2}{c}{**No. _E. coli_****Clinical (_n = 41_)} & \multirow{2}{*}{
\begin{tabular}{c} \(p\) **Value For The Resistant** \\ **Strains of Both Groups** \\ \end{tabular} } \\ \cline{2-3} \cline{5-8}  & **R (\%)** & **I (\%)** & **S (\%)** & **R (\%)** & **I (\%)** & **S (\%)** & **Strains of Both Groups** \\ \hline AM & 6 (5.5) a & 0 (0.0) & 103 (94.5) & 2 (4.9) a & 0 (0.0) & 39 (95.1) & 0.85 \\ SAM & 1 (0.7) a & 0 (0.0) & 108 (99.1) & 0 (0.0) a & 0 (0.0) & 41 (100.0) & 0.40 \\ AMC & 31 (28.4) a & 0 (0.0) & 78 (71.6) & 10 (24.4) a & 0 (0.0) & 31 (75.6) & 0.52 \\ PIP & 6 (5.5) a & 2 (1.8) & 101 (92.7) & 1 (2.4) a & 1 (2.4) & 39 (95.1) & 0.26 \\ TZP & 0 (0.0) a & 2 (1.8) & 107 (98.2) & 0 (0.0) a & 1 (2.4) & 40 (97.6) & 1.00 \\ TIC & 13 (11.9) a & 0 (0.0) & 96 (88.1) & 3 (7.3) a & 0 (0.0) & 38 (92.7) & 0.29 \\ TIM & 8 (7.3) a & 0 (0.0) & 101 (92.7) & 2 (4.9) a & 0 (0.0) & 39 (95.1) & 0.47 \\ CTX & 0 (0.0) a & 0 (0.0) & 109 (100.0) & 0 (0.0) a & 1 (2.4) & 40 (97.6) & 0.12 \\ FOX & 0 (0.0) a & 0 (0.0) & 109 (100.0) & 1 (2.4) a & 0 (0.0) & 40 (97.6) & 0.12 \\ CAZ & 1 (0.9) a & 4 (3.7) & 104 (95.4) & 0 (0.0) b & 6 (14.6) & 35 (85.4) & 0.02 \\ CRO & 0 (0.0) a & 0 (0.0) & 109 (100.0) & 0 (0.0) a & 0 (0.0) & 41 (100.0) & 1.00 \\ CTP & 4 (3.7) a & 0 (0.0) & 105 (96.3) & 1 (2.4) a & 0 (0.0) & 40 (97.6) & 0.59 \\ CXM & 0 (0.0) a & 0 (0.0) & 109 (100.0) & 0 (0.0) a & 0 (0.0) & 41 (100.0) & 1.00 \\ FEP & 0 (0.0) a & 1 (1.8) & 108 (99.1) & 0 (0.0) a & 0 (0.0) & 41 (100.0) & 1.00 \\ DOR & 0 (0.0) a & 0 (0.0) & 109 (100.0) & 0 (0.0) a & 0 (0.0) & 41 (100.0) & 1.00 \\ ETP & 0 (0.0) a & 0 (0.0) & 109 (100.0) & 0 (0.0) a & 1 (2.4) & 40 (97.6) & 1.00 \\ IPM & 0 (0.0) a & 0 (0.0) & 109 (100.0) & 0 (0.0) a & 1 (2.4) & 40 (97.6) & 1.00 \\ MEM & 0 (0.0) a & 0 (0.0) & 109 (100.0) & 0 (0.0) a & 0 (0.0) & 41 (100.0) & 1.00 \\ ATM & 2 (1.8) a & 10 (9.2) & 97 (89.0) & 0 (0.0) a & 1 (2.4) & 40 (97.6) & 0.18 \\ CIP & 0 (0.0) a & 6 (5.5) & 103 (94.5) & 2 (3.4) a & 3 (7.3) & 38 (92.7) & 0.06 \\ LVX & 2 (1.8) a & 6 (5.5) & 101 (92.7) & 0 (0.0) a & 4 (9.8) & 37 (90.2) & 0.53 \\ MXF & 0 (0.0) a & 0 (0.0) & 109 (100.0) & 0 (0.0) a & 0 (0.0) & 41 (100.0) & 1.00 \\ NOR & 7 (6.4) a & 3 (2.8) & 99 (90.8) & 1 (2.4) a & 4 (9.8) & 36 (87.8) & 0.17 \\ OFX & 11 (10.1) a & 1 (0.9) & 97 (89.0) & 4 (9.8) a & 4 (9.8) & 33 (80.5) & 0.09 \\ AN & 1 (0.9) a & 0 (0.0) & 108 (99.1) & 0 (0.0) a & 0 (0.0) & 41 (100.0) & 0.34 \\ \hline \hline \end{tabular}
\end{table}
Table 1: The antimicrobial susceptibility of the tested _E. coli_ strains.  
Production of ESBL was assessed using the double-disk synergy test [21]. _E. coli_ ATCC 25922 (not producing ESBLs) and _Klebsiella pneumoniae_ ATCC 700603 (producing ESBLs) were used as the reference strains.