Genetic mechanisms contributing to reduced tetracycline susceptibility of Campylobacter isolated from organic and conventional dairy farms in the midwestern and northeastern United States.
Campylobacter is one of the most common causes of gastroenteritis and can be acquired through contact with farm animals or the consumption of raw milk. Because of concerns over the role of food-producing animals in the dissemination of antimicrobial resistance to humans, we evaluated the prevalence of antimicrobial resistance in Campylobacter isolates from dairy farms and the genetic mechanism conferring the observed resistance. Evaluation of antimicrobial resistance was completed on 912 isolates from conventional and 304 isolates from organic dairy farms to eight drugs (azithromycin, chloramphenicol, ciprofloxacin, clindamycin, erythromycin, gentamicin, nalidixic acid, and tetracycline) with microbroth dilution. Resistance to seven of eight drugs was very low and did not differ by farm type. However, tetracycline resistance was common in Campylobacter isolated from both organic and conventional dairy farms, with 48 and 58% of isolates affected, respectively. By multiplex PCR, we determined that tetracycline resistance was highly associated with the carriage of tetO in Campylobacter isolates (X2 = 124, P < 0.01, kappa = 0.86).
Population Medicine Center, Michigan State University, East Lansing, Michigan 48824, USA.
Lisa W
LW
Halbert
John B
JB
Kaneene
John
J
Linz
Linda S
LS
Mansfield
Dave
D
Wilson
Pamela L
PL
Ruegg
Lorin D
LD
Warnick
Scott J
SJ
Wells
Charles P
CP
Fossler
Amy M
AM
Campbell
Angela M
AM
Geiger-Zwald
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002167:Campylobacter / Q000187:drug effects* / Q000235:genetics; D002417:Cattle; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D003612:Dairying / Q000379:methods; D004305:Dose-Response Relationship, Drug; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D005516:Food Microbiology; D008826:Microbial Sensitivity Tests; D008892:Milk / Q000382:microbiology*; D016133:Polymerase Chain Reaction; D013752:Tetracycline / Q000494:pharmacology*; D014481:United States
D000900:Anti-Bacterial Agents; D013752:Tetracycline