In Vitro Antimicrobial Activity of Contezolid Against Mycobacterium tuberculosis and Absence of Cross-Resistance with Linezolid

Tuberculosis (TB) persists as a formidable global health threat, especially with the rising incidence of multidrug-resistant strains. This study aimed to evaluate the in vitro activity of contezolid, a novel oxazolidinone antibiotic, against <i>Mycobacterium tuberculosis</i> (<i>Mtb</i>) and assess potential cross-resistance with linezolid. Thirty-one <i>Mtb</i> clinical isolates (5 susceptible, 8 multidrug-resistant [MDR], 18 pre-extensively drug-resistant [pre-XDR]) were tested. Minimum inhibitory concentrations (MICs) of contezolid and linezolid were determined, along with mutation resistance frequencies. Intracellular replication inhibition in macrophages and whole-genome sequencing of resistant colonies were assessed. Cytotoxicity was evaluated via luciferase-coupled ATP assay. The MIC50 and MIC90 values of contezolid were comparable to those of linezolid. Contezolid induced higher mutation frequencies in 7 isolates. At 12 mg/L, both drugs similarly inhibited intracellular <i>Mtb</i> replication. Whole-genome sequencing revealed that the <i>mce3R</i> gene was linked to contezolid resistance, with no cross-resistance observed between two drugs. No significant cytotoxicity was observed in contezolid-treated mouse peritoneal macrophages (<i>p</i> > 0.05). Contezolid exhibits anti-<i>Mtb</i> activity, with <i>mce3R</i> potentially associated with resistance. No cross-resistance with linezolid was found.