title: Antimicrobial resistance of Escherichia coli O157 isolated from humans, cattle, swine, and food.
abstract: A total of 361 Escherichia coli O157 isolates, recovered from humans, cattle, swine, and food during the years 1985 to 2000, were examined to better understand the prevalence of antimicrobial resistance among these organisms. Based on broth microdilution results, 220 (61%) of the isolates were susceptible to all 13 antimicrobials tested. Ninety-nine (27%) of the isolates, however, were resistant to tetracycline, 93 (26%) were resistant to sulfamethoxazole, 61 (17%) were resistant to cephalothin, and 48 (13%) were resistant to ampicillin. Highest frequencies of resistance occurred among swine isolates (n = 70), where 52 (74%) were resistant to sulfamethoxazole, 50 (71%) were resistant to tetracycline, 38 (54%) were resistant to cephalothin, and 17 (24%) were resistant to ampicillin. Based on the presence of Shiga toxin genes as determined by PCR, 210 (58%) of the isolates were identified as Shiga toxin-producing E. coli (STEC). Among these, resistance was generally low, yet 21 (10%) were resistant to sulfamethoxazole and 19 (9%) were resistant to tetracycline. Based on latex agglutination, 189 (52%) of the isolates were identified as E. coli O157:H7, among which 19 (10%) were resistant to sulfamethoxazole and 16 (8%) were resistant to tetracycline. The data suggest that selection pressure imposed by the use of tetracycline derivatives, sulfa drugs, cephalosporins, and penicillins, whether therapeutically in human and veterinary medicine or as prophylaxis in the animal production environment, is a key driving force in the selection of antimicrobial resistance in STEC and non-STEC O157.
authors.affiliation: Department of Nutrition and Food Science, 3304 Marie Mount Hall, University of Maryland, College Park, MD 20742, USA.
authors.forename: Carl M
authors.initials: CM
authors.lastname: Schroeder
authors.forename: Cuiwei
authors.initials: C
authors.lastname: Zhao
authors.forename: Chitrita
authors.initials: C
authors.lastname: DebRoy
authors.forename: Jocelyn
authors.initials: J
authors.lastname: Torcolini
authors.forename: Shaohua
authors.initials: S
authors.lastname: Zhao
authors.forename: David G
authors.initials: DG
authors.lastname: White
authors.forename: David D
authors.initials: DD
authors.lastname: Wagner
authors.forename: Patrick F
authors.initials: PF
authors.lastname: McDermott
authors.forename: Robert D
authors.initials: RD
authors.lastname: Walker
authors.forename: Jianghong
authors.initials: J
authors.lastname: Meng
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology*; D024881:Drug Resistance, Bacterial; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary; D019453:Escherichia coli O157 / Q000145:classification / Q000187:drug effects* / Q000302:isolation & purification; D005516:Food Microbiology; D006801:Humans; D008460:Meat / Q000382:microbiology*; D008826:Microbial Sensitivity Tests; D012703:Serotyping; D022621:Shiga Toxin / Q000378:metabolism; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology*
chemical_list: D000900:Anti-Bacterial Agents; D022621:Shiga Toxin