The isolation of antibiotic-resistant Salmonella from retail ground meats.

Background: Salmonella is a leading cause of food-borne illness. The emerge nce of antimicrobial-resistant salmonella is associated with the use of ant ibiotics in animals raised for food; resistant bacteria can be transmitted to humans through foods, particularly those of animal origin. We identified and characterized strains of salmonella isolated from ground meats purchas ed in the Washington, D.C., area. Methods: Salmonella was isolated from samples of ground chicken, beef, turk ey, and pork purchased at three supermarkets. The isolates were characteriz ed by serotyping, antimicrobial-susceptibility testing, phage typing, and p ulsed-field gel electrophoresis. The polymerase chain reaction and DNA sequ encing were used to identify resistance integrons and extended spectrum bet a -lactamase genes. Results: Of 200 meat samples, 41 (20 percent) contained salmonella, with a total of 13 serotypes. Eighty-four percent of the isolates were resistant t o at least one antibiotic, and 53 percent were resistant to at least three antibiotics. Sixteen percent of the isolates were resistant to ceftriaxone, the drug of choice for treating salmonellosis in children. Bacteriophage t yping identified four isolates of Salmonella enterica serotype typhimurium definitive type 104 (DT104), one of DT104b, and two of DT208. Five isolates of S. enterica serotype agona had resistance to 9 antibiotics, and the two isolates of serotype typhimurium DT208 were resistant to 12 antibiotics. E lectrophoretic patterns of DNA that were indistinguishable from one another were repeatedly found in isolates from different meat samples and differen t stores. Eighteen isolates, representing four serotypes, had integrons wit h genes conferring resistance to aminoglycosides, sulfonamides, trimethopri m, and beta -lactams. Conclusions: Resistant strains of salmonella are common in retail ground me ats. These findings provide support for the adoption of guidelines for the prudent use of antibiotics in food animals and for a reduction in the numbe r of pathogens present on farms and in slaughterhouses. National surveillan ce for antimicrobial-resistant salmonella should be extended to include ret ail meats. (N Engl J Med 2001;345:1147-54.) Copyright (C) 2001 Massachusett s Medical Society.