Affiliation:
1. Departments of Medical Laboratory Science and Biotechnology
2. Internal Medicine
3. Pathology, College of Medicine, National Cheng Kung University
4. Department of Pathology, National Cheng Kung University Hospital, Tainan, Taiwan, Republic of China
Abstract
ABSTRACT
The prevalence of three plasmid-mediated quinolone resistance determinants, QnrA, QnrB, and QnrS, among 526 nonreplicate clinical isolates of
Enterobacter cloacae
collected at a Taiwanese university hospital in 2004 was determined by PCR and colony hybridization, and the association of Qnr with the IMP-8 metallo-β-lactamase was investigated. Eighty-six (16.3%) of all isolates were
qnr
positive, and the
qnrA1
-like,
qnrB2
-like, and
qnrS1
-like genes were detected alone or in combination in 3 (0.6%), 53 (10.1%), and 34 (6.5%) isolates, respectively. Among 149 putative extended-spectrum-β-lactamase-producing isolates, 59 (39.6%) isolates, all of which were SHV-12 producers, harbored
qnrA
(0.7%; 1 isolate),
qnrB
(28.9%; 43 isolates), or
qnrS
(12.1%; 18 isolates). Forty-four (78.6%) of 56 IMP-8 producers carried
qnrB
(58.9%; 33 isolates),
qnrS
(25.0%; 14 isolates), or both. PCR and sequence analysis revealed that
qnrA1
was located in a complex
sul1
-type integron that contains
dhr15
,
aadA2
,
qacE
Δ
1
,
sul1
,
orf513
,
qnrA1
,
ampR
, and
qacE
Δ
1
. Conjugation experiments revealed the coexistence of
qnrB
and
bla
IMP-8
on the transferred plasmids and the absence of β-lactamase content on the transferred
qnrS
-positive plasmids. The transferred
bla
IMP-8
-positive plasmids with and without
qnrB
had very similar restriction patterns, suggesting the horizontal mobility of
qnrB
. Pulsed-field gel electrophoresis showed six major patterns among the 44
qnr
-positive IMP-8-producing isolates. Thus, the extremely high prevalence of
qnr
among the metallo-β-lactamase-producing
E. cloacae
isolates in the hospital may be due mainly to the intrahospital spread of a few clones and the dissemination of plasmids containing both
qnrB
and
bla
IMP-8
.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Pharmacology (medical),Pharmacology