Prevalence of plasmid-mediated quinolone resistance and its association with extended-spectrum beta-lactamase and AmpC beta-lactamase in Enterobacteriaceae.
BACKGROUND
We investigated the prevalence of plasmid-mediated quinolone resistance and its association with extended-spectrum beta-lactamase (ESBL) and AmpC beta-lactamase in Enterobacteriaceae.


METHODS
A total of 347 non-duplicated isolates of Enterobacteriaceae were collected between August and October 2006 from 2 hospitals. Qnr determinant screening was conducted using PCR amplification, and all positive results were confirmed by direct sequencing. Qnr-positive strains were determined on the basis of the presence of ESBL and AmpC beta-lactamase genes.


RESULTS
The qnr gene was detected in 47 of 347 clinical Enterobacteriaceae isolates. Among the 47 qnr-positive strains, Klebsiella pneumoniae (N=29) was the most common, followed by Escherichia coli (N=6), Enterobacter cloacae (N=6), Citrobacter freundii (N=5), and Enterobacter aerogenes (N=1). These isolates were identified as qnrA1 (N=6), 8 qnrB subtypes (N=40), and qnrS1 (N=1). At least 1 ESBL was detected in 38 of the 47 qnr-positive strains. Qnr-positive strains also showed high positive rates of ESBL or AmpC beta-lactamase, such as TEM, SHV, CTX-M, and DHA. DHA-1 was detected in 23 of 47 qnr-positive strains, and this was co-produced with 1 qnrA1 and 22 qnrB4. Strains harboring MIR-1T and CMY were also detected among the qnr-positive strains. Antimicrobial-resistance rates of qnr-positive strains to ciprofloxacin, levofloxacin, norfloxacin, nalidixic acid, and moxifloxacin were 51.1%, 46.8%, 46.8%, 74.5%, and 53.2%, respectively.


CONCLUSIONS
The qnr genes were highly prevalent in Enterobacteriaceae, primarily the qnrB subtypes. They were closely associated with EBSL and AmpC beta-lactamase.
Department of Laboratory Medicine, Inje University College of Medicine, 633-165 Gaegeum-dong, Busanjin-gu, Busan, Korea.
Haeng Soon
HS
Jeong
Il Kwon
IK
Bae
Jeong Hwan
JH
Shin
Hee Jung
HJ
Jung
Si Hyun
SH
Kim
Ja Young
JY
Lee
Seung Hwan
SH
Oh
Hye Ran
HR
Kim
Chulhun Ludgerus
CL
Chang
Weon-Gyu
WG
Kho
Jeong Nyeo
JN
Lee
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D004755:Enterobacteriaceae / Q000201:enzymology / Q000235:genetics* / Q000302:isolation & purification; D004756:Enterobacteriaceae Infections / Q000382:microbiology; D014644:Genetic Variation; D006785:Hospitals, University; D006801:Humans; D008826:Microbial Sensitivity Tests; D010957:Plasmids / Q000235:genetics / Q000378:metabolism*; D015363:Quinolones / Q000494:pharmacology*; D001618:beta-Lactamases / Q000096:biosynthesis / Q000235:genetics
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D015363:Quinolones; C048795:AmpC beta-lactamases; D001618:beta-Lactamases