Antibiotic resistance of Salmonella strains isolated from pig slurry

The survival of Salmonella sp. in pig slurry submitted to treatment in a stabilization ponds system from a pig breeding farm in southern Brazil were evaluated. The stabilization ponds system proved to be efficient, reducing 93% of the Salmonella sp. population present in the slurry. The resistance pattern of 161 Salmonella Typhimurium strains isolated throughout the system were evaluated against 14 antibiotics, using the agar diffusion method. Salmonella strains were resistant to sulfonamide (100%), tetracycline (99.4%), streptomycin (90.1%), sulfamethoxazole/ trimethoprin (84.5%), nalidixic acid (77.6%), ampicillin (76.4%), cloramphenicol (29.2%), cefaclor (25.5%), tobramycin (13.7%), gentamicin (6.2%), amoxacilin/clavulanic acid (5%), neomycin (5%), and amikacin (3.7%). All tested Salmonella strains were sensitive to ciprofloxacin. Most strains of Salmonella (94.5%) were resistant to four or more antibiotics. The multi-resistance pattern was found in strains isolated from all sampled points and were highly variable throughout the system.