Pirlimycin, a lincosamide antibiotic, is effective against gram-positive bacteria, including Staphylococcus, Bacteroides, Streptococcus, and Plasmodium. It functions via inhibiting protein synthesis in bacteria by inducing premature dissociation of the peptidyl-tRNA from the ribosome.

In vitro: Pirlimycin showed activity against Helicobacter pylori with a minimal inhibitory concentration [MIC] 50 of 4 μg/ml and an MIC90 of 64 μg/ml [1].

In vivo: Cows were treated with 50 mg of pirlimycin via two intramammary infusions per quarter at a 24-_x000B_hour interval (2-day) for 2, 5, or 8 days. Pirlimycin showed antibiotic therapy against environmental Streptococcus spp and Staphylococcus aureus intramammary individual and combined infections [1]. Specifically, pirlimycin cured environmental Streptococcus spp infections in 66.7% (14/21), 85% (17/20), 100% (14/14) in the 2-day group, 5-day group and 8-day group, respectively. S. aureus infections were cured by the treatment of pirlimycin in 13.3% (2/15), 31.3% (5/16), 83.3% (5/6) in the 2-day group, 5-day group and 8-day group, respectively. Furthermore, S. aureus, S. dysgalactiae subsp dysgalactiae, and Enterococcus spp intramammary infections were eliminated by the extended treatment of pirlimycin in 8-day group [2].

References:
[1].  Westblom, T., Midkiff, B., & Czinn, S. In vitro susceptibility ofHelicobacter pylori to trospectomycin, pirlimycin (U-57930E), mirincamycin (U-24729A) and N-demethyl clindamycin (U-26767A). European Journal of Clinical Microbiology & Infectious Diseases. 1993; 12(7): 560-562.
[2].  B. E. Gillespie, H. Moorehead, P. Lunn, H. H. Dowlen, D. L. Johnson, K. C. Lamar, M. J. Lewis, S. J. Ivey, J. W. Hallberg, S. T. Chester, and S. P. Oliver. Efficacy of extended pirlimycin hydrochloride therapy for treatment of environmental Streptococcus spp and Staphylococcus aureus intramammary infections in lactating dairy cows. Veterinary Therapeutics. 2002; 3(4): 373-80.