Evaluation of the Antimicrobial Resistance of Different Serotypes of Salmonella enterica from Livestock Farms in Southern Italy

The antimicrobial susceptibility profiles of Salmonella spp. isolated from livestock production systems in Sicily were determined. The antibiotic sensitivity of isolated Salmonella spp. and broad-spectrum beta-lactamase strains were assessed by detecting beta-lactamases blaCTX-M IV, TEM, and OXA SHV, and beta-lactamases blaCMY II, CTX-M I, CTX-M II, and DHA. In total, 93.3% of Salmonella spp. strains showed multi-drug resistance (MDR). A total of seven serotypes (i.e., Salmonella Infantis, S. Typhimurium (monophasic), S. Derby, S. Hadar, S. salamae, S. houtenae, S. Cardoner) showed high resistance values (R) (100-47%) to sulfonamides, tetracyclines, diaminopyrimidines, penicillins, and quinolones. The gene for beta-lactamase blaTEM was found in S. Typhimurium (monophasic) and S. Derby, isolated from swine meat and feces samples; S. Hadar isolated from an insect sample; S. salamae isolated from an abrasive sponge on swine skin; S. houtenae isolated from chicken skin samples; and S. Cardoner isolated from a chicken meat sample. The gene blaCTX-M I was found in S. Infantis isolated from a chicken meat sample. The results gathered in the current study suggest that the resistance to antibiotics is continuously increasing. This represents a worrying perspective since they should be usually used as the last option for therapy against bacterial infections.