Antibiotics
Relative Contributions of Quinolone Resistance-Determining Region Mutations and Efflux Pump-Associated Mechanisms to Fluoroquinolone Resistance in Staphylococcus aureus Clinical Isolates and Their Associations with Virulence Gene Profiles
By Sohyeong Kim, Sohyeong Kim, Heechul Park and 12 others.
Abstract
Background
Fluoroquinolone resistance in methicillin-resistant Staphylococcus aureus (MRSA) involves multiple mechanisms, including quinolone resistance-determining region (QRDR) mutations and efflux pump activity. However, the relationship between these resistance mechanisms and virulence factors (VFs) remains unclear. This study investigated the relative contributions of QRDR mutations and carbonyl cyanide 3-chlorophenylhydrazone (CCCP)-responsive mechanisms to fluoroquinolone resistance in MRSA and their associations with VF profiles.
Methods
Sixty ciprofloxacin-resistant MRSA bloodstream isolates were analyzed. The minimum inhibitory concentrations (MICs) of ciprofloxacin (CIP) and levofloxacin (LEV) were determined before and after treatment with the efflux pump inhibitor CCCP. The isolates were classified as CCCP responsive or non-responsive based on a ≥4-fold reduction in CIP MICs. The associations of QRDR mutations in gyrA, gyrB, parC, and parE and virulence-associated genes with CCCP responsiveness were evaluated.