In vitro pharmacodynamics of nemonoxacin and other antimicrobial agents against Mycoplasma pneumoniae

Mycoplasma pneumoniae is the causative agent of respiratory infections in children and adults. Macrolide still plays a significant role in treating infections by M. pneumoniae. However, macrolide-resistant M. pneumoniae (MRMP) was encountered, causing more severe or prolonged disease worldwide from the early 2000s. Nemonoxacin is a newly developed C-8-methoxy non-fluorinated quinolone having broad-spectrum activity against gram-positive, gram-negative, and atypical pathogens in vitro, as well as general safety and well tolerance in vivo. This study aimed to assess the killing kinetics of nemonoxacin and other antimicrobial agents against MRMP and macrolide susceptible M. pneumoniae (MSMP) by static time-kill curves. In addition, the pharmacodynamic analyses of these drugs were determined by the sigmoid E-max model. The static time-kill curves indicated that nemonoxacin had good mycoplasmacidal activity against both MSMP and MRMP strains. The pharmacodynamic analysis demonstrated that the mycoplasmacidal effect of nemonoxacin was greater than those of moxifloxacin and levofloxacin based on the K-max, displaying a dualism of concentration dependency in low minimum inhibitory concentrations (MICs) and time dependency in high MICs. Therefore, nemonoxacin demonstrated efficacy against M. pneumoniae in vitro and is a potential candidate for clinical studies for assessing its therapeutic effects against M. pneumoniae infections. The killing pattern or PK/PD characteristics of nemonoxacin against M. pneumoniae from in vitro data, animal studies, or clinical studies merit further evaluation for treating infections caused by the organism.