Identification of qnrVF in a Multidrug-Resistant Vibrio furnissii Clinical Strain

We found a new qnr gene, qnrVF1, carried by a multidrug resistance plasmid in a clinical Vibrio furnissii isolate. QnrVF1 exhibits 44.6% to 72.5% similarity in identity with other Qnr family proteins. QnrVF alleles are mainly encoded by chromosomes of V. furnissii and Vibrio fluvialis. Phylogenic analysis showed that QnrVF1 and QnrVF2 form a distinct clade in Qnr proteins. Thus, qnrVF represents a new qnr family. In addition, the qnrVF1 gene is often flanked by the mobile element ISCR1. Thus, it is likely that qnrVF1 is mobilized by ISCR1 from chromosome to plasmid in V. furnissii. IMPORTANCE Quinolones are widely used drugs. Bacteria contain a quinolone resistance gene, which mediates resistance to quinolones. Currently, seven families of Qnr proteins, QnrVC, QnrA, QnrB, QnrC, QnrD, QnrE, and QnrS, have been identified. However, it is unclear whether there are any other qnr families. In this study, we identified a new qnr family, qnrVF. We found many V. furnissii and V. fluvialis strains that possess chromosomal qnrVF alleles, suggesting that V. furnissii and V. fluvialis are the reservoirs of qnrVF. We also found that QnrVF1 confers low-level resistance to quinolones. ISCR1 may facilitate the spread of qnrVF1. The emergence and spread of qnrVF may pose a considerable threat to public health.