title: Effects of Menthol Supplementation in Feedlot Cattle Diets on the Fecal Prevalence of Antimicrobial-Resistant Escherichia coli.
abstract: The pool of antimicrobial resistance determinants in the environment and in the gut flora of cattle is a serious public health concern. In addition to being a source of human exposure, these bacteria can transfer antibiotic resistance determinants to pathogenic bacteria and endanger the future of antimicrobial therapy. The occurrence of antimicrobial resistance genes on mobile genetic elements, such as plasmids, facilitates spread of resistance. Recent work has shown in vitro anti-plasmid activity of menthol, a plant-based compound with the potential to be used as a feed additive to beneficially alter ruminal fermentation. The present study aimed to determine if menthol supplementation in diets of feedlot cattle decreases the prevalence of multidrug-resistant bacteria in feces. Menthol was included in diets of steers at 0.3% of diet dry matter. Fecal samples were collected weekly for 4 weeks and analyzed for total coliforms counts, antimicrobial susceptibilities, and the prevalence of tet genes in E. coli isolates. Results revealed no effect of menthol supplementation on total coliforms counts or prevalence of E. coli resistant to amoxicillin, ampicillin, azithromycin, cefoxitin, ceftiofur, ceftriaxone, chloramphenicol, ciprofloxacin, gentamicin, kanamycin, nalidixic acid, streptomycin, sulfisoxazole, and sulfamethoxazole; however, 30 days of menthol addition to steer diets increased the prevalence of tetracycline-resistant E. coli (P < 0.02). Although the mechanism by which menthol exerts its effects remains unclear, results of our study suggest that menthol may have an impact on antimicrobial resistance in gut bacteria.
authors.affiliation: Departments of Animal Sciences and Industry, Kansas State University, Manhattan, Kansas, United States of America.
authors.forename: C C
authors.initials: CC
authors.lastname: Aperce
authors.affiliation: Diagnostic Medicine and Pathobiology, Kansas State University, Manhattan, Kansas, United States of America.
authors.forename: R
authors.initials: R
authors.lastname: Amachawadi
authors.affiliation: Departments of Animal Sciences and Industry, Kansas State University, Manhattan, Kansas, United States of America.
authors.forename: C L
authors.initials: CL
authors.lastname: Van Bibber-Krueger
authors.affiliation: Diagnostic Medicine and Pathobiology, Kansas State University, Manhattan, Kansas, United States of America.
authors.forename: T G
authors.initials: TG
authors.lastname: Nagaraja
authors.affiliation: Diagnostic Medicine and Pathobiology, Kansas State University, Manhattan, Kansas, United States of America.
authors.forename: H M
authors.initials: HM
authors.lastname: Scott
authors.affiliation: Diagnostic Medicine and Pathobiology, Kansas State University, Manhattan, Kansas, United States of America.
authors.forename: J
authors.initials: J
authors.lastname: Vinasco-Torre
authors.affiliation: Departments of Animal Sciences and Industry, Kansas State University, Manhattan, Kansas, United States of America.
authors.forename: J S
authors.initials: JS
authors.lastname: Drouillard
mesh_terms: D000821:Animal Feed; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000982:Antipruritics / Q000008:administration & dosage; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy* / Q000453:epidemiology / Q000382:microbiology; D019587:Dietary Supplements; D024901:Drug Resistance, Multiple, Bacterial / Q000187:drug effects*; D004926:Escherichia coli / Q000187:drug effects* / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000188:drug therapy / Q000382:microbiology / Q000662:veterinary*; D005243:Feces / Q000382:microbiology; D006801:Humans; D008297:Male; D008610:Menthol / Q000008:administration & dosage*; D008826:Microbial Sensitivity Tests; D015995:Prevalence
chemical_list: D000900:Anti-Bacterial Agents; D000982:Antipruritics; D008610:Menthol