title: Retrospective analysis of Salmonella, Campylobacter, Escherichia coli, and Enterococcus in animal feed ingredients.
abstract: The presence and antimicrobial susceptibility of foodborne pathogens and indicator organisms in animal feed are not well understood. In this study, a total of 201 feed ingredient samples (animal byproducts, n=122; plant byproducts, n=79) were collected in 2002 and 2003 from representative rendering plants and the oilseed (or cereal grain) industry across the United States. The occurrence and antimicrobial susceptibility of four bacterial genera (Salmonella, Campylobacter, Escherichia coli, and Enterococcus) were determined. Salmonella isolates were further characterized by serotyping and pulsed-field gel electrophoresis (PFGE). None of the samples yielded Campylobacter or E. coli O157:H7, whereas Salmonella, generic E. coli, and Enterococcus were present in 22.9%, 39.3%, and 86.6% of samples, respectively. A large percentage (47.8%) of Salmonella-positive samples harbored two serovars, and the vast majority (88.4%) of Enterococcus isolates were E. faecium. Animal byproducts had a significantly higher Salmonella contamination rate (34.4%) than plant byproducts (5.1%) (p<0.05). Among 74 Salmonella isolates recovered, 27 serovars and 55 PFGE patterns were identified; all were pan-susceptible to 17 antimicrobials tested. E. coli isolates (n=131) demonstrated similar susceptibility to these antimicrobials except for tetracycline (15.3% resistance), sulfamethoxazole (7.6%), streptomycin (4.6%), ampicillin (3.8%), and nalidixic acid (1.5%). Enterococcus isolates (n=362) were also resistant to five of 17 antimicrobials tested, ranging from 1.1% to penicillin to 14.6% to tetracycline. Resistance rates were generally higher among isolates recovered from animal byproducts. Taken together, our findings suggest that diverse populations of Salmonella, E. coli, and Enterococcus are commonly present in animal feed ingredients, but antimicrobial resistance is not common. Future large-scale studies to monitor these pathogenic and indicator organisms in feed commodities is warranted.
authors.affiliation: Division of Animal and Food Microbiology, Office of Research, Center for Veterinary Medicine , U.S. Food and Drug Administration, Laurel, Maryland 20708, USA. beilei.ge@fda.hhs.gov
authors.forename: Beilei
authors.initials: B
authors.lastname: Ge
authors.forename: Patricia C
authors.initials: PC
authors.lastname: LaFon
authors.forename: Peggy J
authors.initials: PJ
authors.lastname: Carter
authors.forename: Shawn D
authors.initials: SD
authors.lastname: McDermott
authors.forename: Jason
authors.initials: J
authors.lastname: Abbott
authors.forename: Althea
authors.initials: A
authors.lastname: Glenn
authors.forename: Sherry L
authors.initials: SL
authors.lastname: Ayers
authors.forename: Sharon L
authors.initials: SL
authors.lastname: Friedman
authors.forename: Joseph C
authors.initials: JC
authors.lastname: Paige
authors.forename: David D
authors.initials: DD
authors.lastname: Wagner
authors.forename: Shaohua
authors.initials: S
authors.lastname: Zhao
authors.forename: Patrick F
authors.initials: PF
authors.lastname: McDermott
authors.forename: Mark A
authors.initials: MA
authors.lastname: Rasmussen
mesh_terms: D000821:Animal Feed / Q000382:microbiology*; D000818:Animals; D002167:Campylobacter / Q000187:drug effects / Q000302:isolation & purification*; D015169:Colony Count, Microbial; D024901:Drug Resistance, Multiple, Bacterial / Q000187:drug effects; D016521:Electrophoresis, Gel, Pulsed-Field; D016983:Enterococcus / Q000187:drug effects / Q000302:isolation & purification*; D004926:Escherichia coli / Q000187:drug effects / Q000302:isolation & purification*; D005506:Food Contamination; D005516:Food Microbiology; D008460:Meat / Q000382:microbiology*; D008826:Microbial Sensitivity Tests; D012475:Salmonella / Q000187:drug effects / Q000302:isolation & purification*; D012703:Serotyping; D014481:United States