The aim of this study was to determine the prevalence of qnr genes among 93 consecutive nonrepetitive Enterobacteriaceae isolates from chickens (n=37) and pigs (n=56) near Seoul, South Korea in 2007, and to characterize positive isolates. PCR-based detection and sequencing were used to investigate plasmid-mediated quinolone resistance (PMQR) determinants and quinolone resistance-determining region (QRDR) mutations. Two isolates (2.2%) were found to carry novel qnrB variants: qnrB22 in Citrobacter werkmanii PS012 (isolated from a pig) and qnrB23 in Citrobacter freundii S008 (isolated from a chicken). Sequence analysis showed qnrB22 had 99.7% nucleotide identity with qnrB4, with the deduced QnrB22 protein having two amino acid substitutions (Ser36Cys and Gly188Val) compared to QnrB4; qnrB23 had 99.9% nucleotide identity with qnrB9, with QnrB23 having one amino acid substitution (Asn27Tyr) compared to QnrB9. C. werkmanii PS012 showed reduced susceptibility to fluoroquinolones (ofloxacin, norfloxacin, levofloxacin, ciprofloxacin), while C. freundii S008 was nonsusceptible to these agents, and no QRDR mutations associated with fluoroquinolone resistance were detected in either isolate. Conjugative plasmids harboring qnrB22 or qnrB23 were transferred to Escherichia coli J53 AzideR, and transconjugants had similar fluoroquinolone minimum inhibitory concentrations (MICs) to the donor strains. Cloning of qnrB22 and qnrB23 into E. coli DH5 confirmed they conferred reduced quinolone susceptibility. The plasmids belonged to the IncL/M incompatibility group. Despite the low prevalence (2.2%) of qnrB22 and qnrB23, surveillance for bacterial isolates carrying these resistance determinants in animals is warranted.