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

Background: Stenotrophomonas sepilia, identified in 2021, is part of the Stenotrophomonas maltophilia complex (Smc) and shares high genomic identity with S. maltophilia. Resistance to levofloxacin, the recommended fluoroquinolone for S. maltophilia, 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 S. sepilia.

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

Methods: A total of 116 S. maltophilia isolates, identified by MALDI-TOF MS, were collected from five centres across India. S. sepilia 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 S. maltophilia isolates collected, 46 were identified as S. sepilia, 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 S. sepilia tested. Only one S. sepilia isolate resistant to levofloxacin showed intermediate susceptibility to levonadifloxacin, which consistently had lower MICs.

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