Repetitive sequence-based PCR fingerprinting and the relationship of antimicrobial-resistance characteristics and corresponding genes among Salmonella strains from pig production

Abstract Objective To investigate the relationship between antimicrobial resistance characteristics and corresponding genes, and to diversify repetitive element sequence-based PCR (rep-PCR) fingerprinting of three Salmonella serotypes: Rissen, Panama and Stanley, which were isolated from pig farms and slaughterhouses in Chiang Mai and Lumphun Provinces, Thailand. Methods A total of 90 Salmonella strains were identified using the Kauffman-White scheme. The Kirby-Bauer disk diffusion method was used to investigate resistance phenotypes of 10 antimicrobial agents. Conventional PCR was used to detect 10 antimicrobial resistance genes, additionally, rep-PCR typing method was applied to identify clonality among Salmonella isolates. Results The antimicrobial susceptibility testing found resistance to ampicillin (80.0%), streptomycin (65.6%), tetracycline (61.1%), sulfamethoxazole (53.3%), chloramphenicol (28.9%), nalidixic acid (6.7%) and cefotaxime (2.2%). All strains were sensitive to amoxicillin-clavulanic acid, ciprofloxacin and norfloxacin. The most common antimicrobial resistance patterns among the isolates were ampicillin, chloramphenicol, streptomycin, tetracycline, and sulfamethoxazole. The type and frequency of antimicrobial genes detected included bla TEM (100.0%), aad A2 (52.2%), cml A (45.6%), str A (38.9%), tet A(B) (16.7%), sul 1 (15.6%), bla OXA-2 (14.4%), bla PSE1 (6.7%), aph A1-lab (2.2%) and blaCMY-2 (1.1%). Conclusions Statistical analysis revealed no association between antimicrobial resistance genes and resistance profiles with the exception of cml A and chloramphenicol, sul 1 and sulfamethoxazole, aad A2 and streptomycin, and str A and streptomycin ( P Salmonella genotypes from farms and from slaughterhouses.