Incidence of Drug Resistance and R-factor Among Salmonellae Isolated from Poultry ,

Abstract

Studies to determine the drug resistance of Salmonella isolates to nine antimicrobial agents were conducted with a single disc diffusion method. Isolates sensitive to nalidixic acid and resistant to chlortetracycline or dihydrostreptomycin or both were tested for their ability to transfer drug resistance to Escherichia coli K-12NA in vitro.Among the 106 Salmonella cultures examined for drug resistance, 44.3 percent were resistant to one or more antimicrobial agents. None of the Salmonella isolates were resistant to chloramphenicol, gentamicin or nalidixic acid and few isolates were resistant to furazolidone and colistin. Resistance to dihydrostreptomycin, followed by resistance to the tetracyclines, was most common among the Salmonella isolates. More than 50 percent of the Salmonella isolates tested transferred all or part of their resistance patterns to E. codi K-12NA. Multiple-drug-resistant strains were more efficient in transferring their resistance patterns than were single-drug-resistant strains.Resistance among the most frequently occurring non-human serotypes tested was most common in isolates of S. heidelberg (71.4%), followed by S. typhimurium (53.3%), S. saint paul (50.0%), S. senftenberg (37.7%) and S. infantis (14.2%).