Fluoroquinolone Resistance Mechanisms by Molecular Epidemiologic Study of Ciprofloxacin-Nonsusceptible Escherichia coli Sequence Types Isolated from Clinical Specimens in a Tertiary Care University Hospital in Korea: Emergence of Clone ST131, 2006-2008.

To investigate the sequence types (STs) and fluoroquinolone resistance related mutations among ciprofloxacin (CIP)-non-susceptible extended-spectrum β-lactamase (ESBL)-producing E. coli isolated from Korean patients from 2006-2008. The prevalence of fluoroquinolone resistance-determining region (QRDR) mutations in gyrA, gyrB, parC, and parE and plasmid-mediated quinolone resistance (PMQR) genes were also studied. Multilocus sequence typing (MLST) was performed to identify STs. The most common ST was ST131 (33/51, 64.7%). All isolates, except one isolate, showed three mutations at codons 83 (S83L) and 87 (S87N) in gyrA and 80 (S80I) in parC The prevalence of ST131 in our hospital was much higher than reported in other Asian studies during a similar time period. The mutations found in ST131 were concordant with other studies.