Abstract:

Escherichia coli strains were isolated from 130 pork samples collected in Sichuan province usingselective medium and confirmed by VITEK. The susceptibility of the isolated E. coli strains to ten antibiotics wastested according to the standard disk diffusion method of the Clinical and Laboratory Standards Institute (CLSI).The minimum inhibitory concentrations (MICs) of three quaternary ammonium compounds (QACs) against thesestrains were determined by an agar dilution method. QAC resistance genes were amplified using ten different sets ofprimers. The results showed that 96 E. coli strains were obtained with frequency of 73.85%. The resistance frequencyto tetracycline (TET), ampicillin (AMP), streptomycin (S), kanamycin (K), ceftofur (KF), ciprofloxacin (CIP),gentamicin (CN) ampicillin/sulbactam (SAM), ceftazidime (CAZ) and ceftriaxone (CRO) was 64.58%, 37.50%,32.29%, 21.88%, 20.83%, 18.75%, 9.38%, 6.25%, 2.08% and 2.08%, respectively. There were 28 different antibioticresistance profiles Among these, TET profile was the dominant one. The MICs of benzalkonium chloride (BC),didecyldimethylammonium chloride (DDAC) and etrimonium bromide (CTAB) against E. coli were 16－64 μg/mL,8－32 μg/mL, and 64－256 μg/mL, respectively. ydgE/F（81.25%）was the most prevalent QAC resistance gene inE. coli, followed by mdfA (50%), sugE(c) (45.83%), emrE (36.46%), qacEΔ1 (19.79%), qacF (17.71%), qacE (14.58%)and sugE(p) (3.13%). And qacG－ was not detected in any of the isolates. There were 42 different qac resistance genegroups (1.04%－12.50%). Both sugE(c)and qacF gene were commonly present in aminoglycoside and AMP resistant E. coli, and qacEΔ1 gene was also related with AMP resistance. The resistance frequency and multi-drug resistancewere lower than those of other reports. The frequency of QAC resistance genes and the MIC of QACs were high,suggesting that the E. coli from pork may be a reservoir of antibacterial resistance.

Key words: pork, Escherichia coli, drug resistance, disinfectants