Susceptibility of clinical isolates of novel pathogen to novel benzoquinolizine fluoroquinolone levonadifloxacin.

Background: , identified in 2021, is part of the complex (Smc) and shares high genomic identity with . Resistance to levofloxacin, the recommended fluoroquinolone for , is being increasingly reported. Recent studies indicate that levonadifloxacin, a novel benzoquinolizine, may be more effective. This study evaluates the antimicrobial efficacy of levofloxacin and levonadifloxacin against clinical isolates of .

Objectives: To assess the antibacterial effectiveness of levofloxacin and levonadifloxacin against novel pathogen

Methods: A total of 116 isolates, identified by MALDI-TOF MS, were collected from five centres across India. was confirmed by PCR using primers targeting a unique genomic sequence (NCBI accession number LXXZ00000000.1). Minimum inhibitory concentrations (MICs) of levonadifloxacin and levofloxacin were determined by using the microbroth-dilution method and Etest as per CLSI guidelines. The levofloxacin breakpoint was used to interpret MICs of levonadifloxacin.

Results: Among a total of 116 circulating isolates collected, 46 were identified as , representing a prevalence rate of (∼40%), thus highlighting its significance as an important pathogen within the Smc. Both levofloxacin and levonadifloxacin demonstrated a 98% inhibition rate against the 46 tested. Only one isolate resistant to levofloxacin showed intermediate susceptibility to levonadifloxacin, which consistently had lower MICs.

Conclusions: Levofloxacin and levonadifloxacin show similar susceptibility rates against , with levonadifloxacin exhibiting lower MICs. Further studies are required to establish clinical utility of levonadifloxacin in managing these infections.