title: Antimicrobial susceptibility of Shiga toxin-producing Escherichia coli isolated from organic dairy farms, conventional dairy farms, and county fairs in Minnesota.
abstract: This study compared the antimicrobial susceptibility of Shiga toxin-producing Escherichia coli (STEC) isolates from organic dairy farms, conventional dairy farms, and Minnesota county fairs. A total of 83 STEC isolates (43 O157 and 40 non-O157 STEC) were tested for antimicrobial susceptibility as determined by the automated broth microdilution method. Resistance to tetracycline was identified in 19 (23%) isolates and to sulphadimethoxine in 40 (48%) isolates. Half of the STEC isolates were resistant to at least one antimicrobial agent. Resistance to at least one antimicrobial agent was observed in 18 (62%) isolates from conventional farms and in 11 (48%) isolates from organic farms. Resistance to at least one antimicrobial agent was more frequent in isolates from calves (77%) than from cows (39%). Multidrug resistant patterns were more common in non-O157 STEC than O157 STEC. This study provides data to document the degree of STEC antimicrobial resistance from dairy cattle sources in Minnesota. The use of antimicrobial agents on farms, and other environmental influences, may affect resistance patterns in isolates from cattle sources. Systematic surveillance of STEC from cattle could potentially detect emergence of antimicrobial resistance that may be spread to humans through the food chain.
authors.affiliation: Department of Veterinary Population Medicine, University of Minnesota, Minneapolis, Minnesota 55108, USA. bende002@umn.edu
authors.forename: Seongbeom
authors.initials: S
authors.lastname: Cho
authors.forename: Charles P
authors.initials: CP
authors.lastname: Fossler
authors.forename: Francisco
authors.initials: F
authors.lastname: Diez-Gonzalez
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Wells
authors.forename: Craig W
authors.initials: CW
authors.lastname: Hedberg
authors.forename: John B
authors.initials: JB
authors.lastname: Kaneene
authors.forename: Pamela L
authors.initials: PL
authors.lastname: Ruegg
authors.forename: Lorin D
authors.initials: LD
authors.lastname: Warnick
authors.forename: Jeffrey B
authors.initials: JB
authors.lastname: Bender
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002417:Cattle; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D003611:Dairy Products / Q000382:microbiology*; D003612:Dairying / Q000379:methods*; D024881:Drug Resistance, Bacterial; D024901:Drug Resistance, Multiple, Bacterial; D004926:Escherichia coli / Q000187:drug effects* / Q000254:growth & development; D019453:Escherichia coli O157 / Q000187:drug effects / Q000254:growth & development; D005506:Food Contamination / Q000032:analysis*; D006801:Humans; D008826:Microbial Sensitivity Tests; D008910:Minnesota
chemical_list: D000900:Anti-Bacterial Agents