Genotypes of Ciprofloxacin-Resistant Klebsiella pneumoniae in Korea and Their Characteristics According to the Genetic Lineages

Abstract

We investigated the molecular genotypes of ciprofloxacin-resistant Klebsiella pneumoniae and their characteristics according to the genetic lineages. For 160 K. pneumoniae collected in 2013, ciprofloxacin minimum inhibitory concentrations (MICs) were determined by agar dilution method. The genotypes of ciprofloxacin-resistant K. pneumoniae isolates were determined by multilocus sequence typing (MLST) and wzi gene typing. The presence of plasmid-mediated resistance determinants [qnrA, qnrB, qnrS, aac(6′)-Ib-cr, bla_CTX-M, and bla_SHV] was investigated. The gyrA and parC genes were sequenced. Fifty-seven isolates showed ciprofloxacin resistance. By MLST, four major sequence types (STs) or clonal complexes (CCs), that is, ST307, CC11, CC147, and ST15, were found and the two most prevalent STs were ST307 (14/57, 24.6%) and ST11 (12/57, 21.1%). By wzi gene sequencing, 46 of the 57 isolates could be differentiated. All the ST307 isolates had an identical wzi sequence and harbored qnrB. The majority of them harbored aac(6′)-Ib-cr (85.7%) and CTX-M-15 (92.9%). In contrast, 12 ST11 isolates were divided into five sublineages by wzi sequence and qnrB, qnrS, and aac(6′)-Ib-cr were carried by nine, seven, and three isolates, respectively. They harbored SHV-type extended-spectrum β-lactamase more frequently than CTX-M-15 (nine and four isolates, respectively). The prevalence of CTX-M-15, qnrB1, and aac(6′)-Ib-cr was significantly higher in ST307 than in ST11 (p=0.003, p=0.000, and p=0.002, respectively). Both clones had identical amino acid substitution in gyrA (S83I) and parC (S80I). K. pneumoniae ST307 and ST11 were the two most common clones, and the ST307 isolates were highly homogeneous, suggesting their recent emergence.