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An increase of multi-drug resistant Escherichia coliin swine husbandry have been concerned worldwide. This study aimed to determine the multidrug resistance and nucleotide substitution of beta-lactam antibiotic and tetracycline resistant genes in E. colifrom swine farms in Southern Thailand. A total of 112 isolates of E. coliwas isolated from 50 pig farms, which were confirmed by identified by MALDI-TOF analysis. Seventy-three isolates (65.18%) and 39 isolates (34.82%) were isolated from the feces and waste water samples, respectively. One hundred percent resistance to beta-lactam antibiotics as well as their resistant gene blaTEMwas detected in isolates. Furthermore, 81% isolates were tetracycline resistance and both tetA[68.42% (13/19) in feces samples, 72.73% (8/11) in waste water samples] and tetB[10.53% (2/19) in feces samples, 18.18% (2/11) in waste water samples] genes responsible for tetracycline resistance were observed. Furthermore, 54 isolates had multi-drug resistance that presented 11 different patterns. The nucleotide substitution of genes was detected in 3 isolates of E. coli, and may consider as the point mutation. The nucleotide at 859 bp of tetAgene of the isolate WU-WW009-01 was changed from T to A. While, the isolate WU-WW004-02 showed 2 nucleotide substitution sites at the position of 266 (from A to G) and 859 (from T to G) bp. The nucleotide at 36 bp of blaTEMgene of the isolate WU-F003-02 was replaced from G to A. Findings of this study may help to control the spread of E. coliantibiotic resistance genes in the swine farms.

Many studies have examined avian pathogenic Escherichia coli(APEC) from commercial broilers but few have examined isolates from native chickens. This study compared APEC isolates from commercial broilers and native chickens in regard to the phylogenetic group and the phenotypic and genotypic antimicrobial resistance profiles. From 100 suspect colibacillosis cases in both commercial broilers and native chickens, a total of 90 broiler isolates and 42 native chicken isolates were identified as E. coliby biochemical tests. Phylogenetic grouping revealed that 90 broiler APEC isolates belonged to A group (5.56%), B1 group (22.22%), B2 group (31.11%), and D group (41.11%). The 42 native chicken APEC isolates belonged to A group (35.71%), B1 group (26.19%), B2 group (30.95%), and D group (7.14%). The difference in the allocation to groups A and D of the 2 isolate types was significant (P< 0.05). The APEC broiler isolates had a significantly higher multidrug-resistant (MDR) rate (80%) than the native chicken isolates (14.29%) (P< 0.05). The APEC broiler isolates demonstrated significantly higher resistance rates than the native chicken isolates for amoxicillin (98.89%; 78.57% respectively), chloramphenicol (42.2%; 9.5%), enrofloxacin (68.9%; 7.1%), gentamicin (11.1%; 0%), nalidixic acid (72.2%; 7.1%), sulfamethoxazole + trimethoprim (45.6%; 2.4%), and tetracycline (88.9%; 76.2%) (P< 0.05). The APEC broiler isolates had a significantly higher presence compared with the native chicken isolates of the following resistance genes:- by blaTEM(43.3%; 21.4%, respectively), cml-A(34.4%; 2.4%), tetA(76.7%; 40.5%), tetB(26.7%; 0%), sul2(23.3%; 14.3%), and dhfrI(13.3%; 0%) (P< 0.05). The qnrBand qnrSgenes were detected (12.16%; 72.97% respectively), in the APEC broiler isolates resistant to nalidixic acid and/or enrofloxacin while only qnrSgenes was detected in all 3 APEC native chicken isolates. Regarding the point mutations of gyrAand parC, all isolates were positive to gyrA83S, gyrA87D, gyrA87L, gyrA87NY, parC80S and parC80I except that gyrA83S was not present in 20 APEC broiler isolates. Antimicrobial stewardship programs should be targeted at the backyard poultry sector as well as the commercial poultry sector.