One Health Perspective of Mycoplasmas: Proposals for Standardizing In Vitro PK/PD Models of Human Mycoplasma Species...

The rising prevalence of macrolide and fluoroquinolone resistance in human pathogenic mycoplasmas, such as Mycoplasma pneumoniae and Mycoplasma genitalium, threatens global public health. Mutations in 23S rRNA and quinolone resistance-determining regions (QRDR) have compromised the first-line therapies, creating an urgent clinical need for alternatives. Consequently, novel antimicrobial agents (pleuromutilins, novel tetracyclines, topoisomerase inhibitors) have become a top research priority. However, standardized in vitro pharmacokinetic/pharmacodynamic (PK/PD) methodologies for mycoplasmas remain underdeveloped compared to typical bacteria. Key challenges include the lack of a cell wall, slow growth kinetics, and fastidious culture requirements, which invalidate standard colony-counting and susceptibility testing protocols. This review evaluates current in vitro PK/PD models, quantification techniques, and key indices, highlighting the potential of adapting the methodological frameworks established in veterinary mycoplasma research (e.g., Mycoplasma bovis, Mycoplasma hyopneumoniae) to human mycoplasma species. We specifically analyze the utility of propidium monoazide (PMA)-qPCR for viability assessment and hollow-fiber infection models (HFIM) configured for small-cell retention. We conclude that harmonizing these methodologies through a One Health approach is critical for optimizing dosing regimens, reducing resistance, and accelerating the development of novel antimicrobial agents for human use.