Background:

Tildipirosin, a long-acting macrolide, has antibiotic activity.

Tildipirosin exhibits the inhibitory effect on C. coli species, and 23 of 31 (74%) isolates have MICs of 8 or 16 μg/mL while 8 of 31 (26%) have MIC >256 μg/mL. MICs against C. jejuni are 8-64 μg/mL. Tildipirosin against S. enterica and E. coli are 2-8 μg/mL[1]. Tildipirosin inhibits the treponeme isolates form from CODD lesions from 19 sheep, with MIC90 of 0.0469 mg/L[3]. The P. multocida B130 clones show the MIC of 0.25 mg/L for tildipirosin. The 10 P. multocida isolates that carry only erm(42) exhibit MIC of 16-32 mg/L for tildipirosin. The single M. haemolytica that harbours only erm(42) shows MIC of 32 mg/L for tildipirosin[4].

The mean percentage of lung consolidation for tildipirosin (4 mg/kg, s.c.)-treated calves is significantly lower than those for tulathromycin-treated and control calves. Metaphylactic administration of tildipirosin to calves 5 days prior to H somni challenge prevents subsequent culture of the pathogen from bronchial secretions and is more effective in minimizing clinical disease and lung lesions than is metaphylactic administration of tulathromycin[2].

[1]. Rose M, et al. A microbiological assay to estimate the antimicrobial activity of parenteral tildipirosin against foodborne pathogens and commensals in the colon of beef cattle and pigs. J Vet Pharmacol Ther. 2016 Jun;39(3):277-86. [2]. Confer AW, et al. Clinical disease and lung lesions in calves experimentally inoculated with Histophilus somni five days after metaphylactic administration of tildipirosin or tulathromycin. Am J Vet Res. 2016 Apr;77(4):358-66. [3]. Angell JW, et al. In vitro susceptibility of contagious ovine digital dermatitis associated Treponema spp. isolates to antimicrobial agents in the UK. Vet Dermatol. 2015 Dec;26(6):484-7, e114-5. [4]. Michael GB, et al. Increased MICs of gamithromycin and tildipirosin in the presence of the genes erm(42) and msr(E)-mph(E) for bovine Pasteurella multocida and Mannheimia haemolytica. J Antimicrob Chemother. 2012 Jun;67(6):1555-7.