QnrVC

qnrVC is a plasmid-borne quinolone resistance gene that encodes the QnrVC protein, a member of the Qnr family of pentapeptide repeat proteins. QnrVC proteins protect bacterial DNA gyrase and topoisomerase IV from the action of fluoroquinolones, leading to reduced drug susceptibility.

QnrVC proteins are typically around 218 amino acids long and share the characteristic pentapeptide repeats that distinguish Qnr family members. The qnrVC gene was first identified in marine Vibrio species and has since been found in diverse Gram-negative bacteria. Variants such as qnrVC1 and qnrVC2 have been reported in environmental and clinical isolates.

qnrVC genes are usually located on plasmids, which facilitates horizontal transfer among bacteria. They are often found on plasmids carrying other resistance determinants and can be associated with mobile genetic elements such as insertion sequences and integrons, enabling dissemination in both environmental reservoirs and clinical settings.

Clinically, qnrVC contributes to low-level fluoroquinolone resistance and can promote the selection of higher-level resistance when combined with additional mechanisms, such as target gene mutations. Detection typically relies on molecular methods, including PCR and sequencing, to identify qnrVC alleles in bacterial isolates.