Abstract
Valnemulin, a semisynthetic pleuromutilin antibiotic derivative, is greatly active against Mycoplasma. The objective of our study was to evaluate the effectiveness of valnemulin against Mycoplasma gallisepticum in a neutropenic intratracheal model in chickens using a pharmacokinetic/pharmacodynamic (PK-PD) method. The PK of valnemulin after intramuscular (i.m.) administration at doses of 1, 10, and 20 mg/kg of body weight in M. gallisepticum-infected neutropenic chickens was evaluated by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Real-time PCR (RT-PCR) was used for quantitative detection of M. gallisepticum. The ratio of the 24-h area under the concentration-time curve divided by the MIC (AUC24/MIC) correlated well with the in vivo antibacterial effectiveness of valnemulin (R(2) = 0.9669). The AUC24/MIC ratios for mycoplasmastasis (a reduction of 0 log10 color-changing unit [CCU] equivalents/ml), a reduction of 1 log10 CCU equivalents/ml, and a reduction of 2.5 log10 CCU equivalents/ml are 28,820, 38,030, and 56,256, respectively. In addition, we demonstrated that valnemulin at a dose of 6.5 mg/kg resulted in a reduction of 2.5 log10 CCU equivalents/ml. These investigations provide a solid foundation for the usage of valnemulin in poultry with M. gallisepticum infections.