Antimicrobial resistance of Salmonella in raw retail chickens, imported chicken portions, and human clinical specimens

Salmonella isolates from raw, chilled, retail chickens (n = 434) sampled between 1998 and 2000 were tested for resistance to 12 antibiotics. Of 23 salmonellas isolated, 30% were susceptible and 30% were resistant or intermediately resistant to one antibiotic, 26% to two, and 13% to four or more. One Salmonella Saint-Paul and two Salmonella Typhimurium isolates were resistant to more than four antibiotics. Highest resistance rates were sulfonamide (52%), streptomycin (26%), tetracycline (22%), and ampicillin (17%). Isolates (n = 27) from frozen chicken portions (n = 150) imported from Brazil and Thailand (generally for manufacturing and catering) were also tested. Brazilian salmonellas showed no multiple resistance, but an isolate of Salmonella Virchow from Thai chickens was resistant to two antibiotics. This compared with 39% resistance to two or more antibiotics in nonimported isolates. Resistance patterns of both sets of chicken isolates were compared with human fecal clinical isolates (n = 274) submitted for routine examination at this hospital, and a greater similarity was found between the clinical and local isolates than with imported salmonellas. Sulfonamide resistance in imported salmonellas was lower than that of nonimported and clinical isolates. Resistance to one or more antimicrobial was found in 70% of nonimported raw retail chickens, 52% of imported chicken breast fillets, and 84% of human fecal isolates. Multiple resistance (to four or more antibiotics) is a much more limited problem.