title: Efficacy of intramammary tilmicosin and risk factors for cure of Staphylococcus aureus infection in the dry period.
abstract: The objective ofthis study was to evaluate the efficacy of intramammary tilmicosin, administered at drying-off, for eliminating Staphylococcus aureus infection, and to identify risk factors for S. aureus cure during the dry period. A total of 219 naturally infected cows, representing 308 quarters, were randomized to receive either one of two treatments at drying-off. Cows received either an intramammary infusion of 500 mg of benzathine cloxacillin, or a sterile solution containing 1,500 mg of tilmicosin. All cows had quarter milk samples taken aseptically three times before dry-off, and at wk 1, 2, and 4 of the subsequent lactation. Overall, 62% of cows and 67.5% of quarters infected with S. aureus cured during the dry period. The cure following administraton of tilmicosin was 67.3 and 72.5% for cows and quarters, respectively. By comparison, the cure achieved with cloxacillin was 56.9 and 62.9% of cows and quarters. Cows receiving tilmicosin were 2.1 times more likely to cure. The cure rate for cows decreased as the linear score on the last DHI test increased, and as the amount of S. aureus being shed increased. Quarters that cultured positive multiple times before drying-off were less likely to cure. Staphylococcus aureus infections located in front quarters of the udder were 2 times more likely to cure than those in hind quarters. Results of this study demonstrate that intramammary tilmicosin at drying-off is efficacious in curing existing S. aureus during the dry period. Risk factors associated with the cure of S. aureus were identified.
authors.affiliation: University of Guelph, Guelph, Ontario N1G 2W1, Canada. rdingwell@vet.k-state.edu
authors.forename: R T
authors.initials: RT
authors.lastname: Dingwell
authors.forename: K E
authors.initials: KE
authors.lastname: Leslie
authors.forename: T F
authors.initials: TF
authors.lastname: Duffield
authors.forename: Y H
authors.initials: YH
authors.lastname: Schukken
authors.forename: L
authors.initials: L
authors.lastname: DesCoteaux
authors.forename: G P
authors.initials: GP
authors.lastname: Keefe
authors.forename: D F
authors.initials: DF
authors.lastname: Kelton
authors.forename: K D
authors.initials: KD
authors.lastname: Lissemore
authors.forename: W
authors.initials: W
authors.lastname: Shewfelt
authors.forename: P
authors.initials: P
authors.lastname: Dick
authors.forename: R
authors.initials: R
authors.lastname: Bagg
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology / Q000627:therapeutic use*; D002417:Cattle; D003023:Cloxacillin / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D015169:Colony Count, Microbial / Q000662:veterinary; D005260:Female; D007774:Lactation; D016015:Logistic Models; D018942:Macrolides; D008321:Mammary Glands, Animal / Q000382:microbiology; D008414:Mastitis, Bovine / Q000188:drug therapy*; D008892:Milk / Q000382:microbiology*; D010298:Parity; D011897:Random Allocation; D012307:Risk Factors; D013203:Staphylococcal Infections / Q000188:drug therapy / Q000662:veterinary*; D013211:Staphylococcus aureus / Q000187:drug effects / Q000254:growth & development; D016896:Treatment Outcome; D015645:Tylosin / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use*
chemical_list: D000900:Anti-Bacterial Agents; D018942:Macrolides; C006692:benzathine cloxacillin; D003023:Cloxacillin; C052319:tilmicosin; D015645:Tylosin