Resumo

Salmonella spp. are important zoonotic pathogens in humans and animals. Increasing rates of antimicrobial resistance in Salmonella isolates have been reported from a number of developing and developed countries. The purpose of our study was to do a preliminary screening to determine the occurrence of antibiotic resistance of Salmonella enterica isolates recovered from animals for diagnostic purposes. We examined 50 strains of 14 serovars isolated for resistance to 20 antibiotics according to CLSI-recommended Kirby-Bauer disk diffusion testing. Strains resistant to extended spectrum cephalosporins were characterized as extended spectrum β-lactamase (ESBL) or AmpC producers by using the CLSI-recommended phenotypic confirmatory test and boronic acid disk potentiation test, respectively. Resistance to tetracycline (46 %) was highest, whereas resistance to ampicillin (12 %), kanamycin (2 %), gentamycin (2 %), chloramphenicol (8 %), trimethoprim-sulfamethoxazole (8 %) and aztreonam (6 %) was low. Four strains showed resistance to 4 to 6 antibiotics, including tetracycline, ampicillin, chloramphenicol and trimethoprim-sulfamethoxazole. None of the strains showed resistance to amikacin, streptomycin, imipenem and meropenem. One S. Typhimurium strain isolated from a foal was resistant to both oxyimino-cephalosporins and cefoxitin. Phenotypic test detected the production of both ESBL and AmpC β-lactamases. The two S. Gallinarum strains showed resistance to nalidixic acid and ciprofloxacin. Antibiotic resistance in Salmonella was intensified substantially today. The extensive use of third-generation cephalosporins has resulted in the increased prevalence of ESBL and plasmid-mediated AmpC among these organisms. In Argentina, ESBL and plasmid-mediated AmpC β-lactamases have been detected in Salmonella strains isolated from humans. On one hand similar, fluoroquinolones are a class of synthetic antimicrobial agents that have been widely used in veterinary medicine in the last years. The development of resistance in S. Gallinarum was reported in many countries. The detection of resistance to ESBL and fluoroquinolones in Salmonella strains isolated from horses and fowl, respectively, should alert us on the spread of resistance genes from companion and food-producing animals to humans, an important fact that constitutes a public health concern.