Affiliation:
1. Lahey Clinic, Burlington
2. Massachusetts General Hospital, Boston, Massachusetts
Abstract
ABSTRACT
A novel plasmid-mediated quinolone resistance gene,
qnrB
, has been discovered in a plasmid encoding the CTX-M-15 β-lactamase from a
Klebsiella pneumoniae
strain isolated in South India. It has less than 40% amino acid identity with the original
qnr
(now
qnrA
) gene or with the recently described
qnrS
but, like them, codes for a protein belonging to the pentapeptide repeat family. Strains with
qnrB
demonstrated low-level resistance to all quinolones tested. The gene has been cloned in an expression vector attaching a polyhistidine tag, which facilitated purification to ≥95% homogeneity. As little as 5 pM of QnrB-His
6
protected purified DNA gyrase against inhibition by 2 μg/ml (6 μM) ciprofloxacin. With a PCR assay
qnrB
has been detected in
Citrobacter koseri
,
Enterobacter cloacae
, and
Escherichia coli
isolates from the United States, linked to SHV-12 β-lactamase and coding for a product differing in five amino acids from the Indian (now QnrB1) variety. The
qnrB
gene has been found near Orf1005 in some, but not all, plasmids and in association with open reading frames matching known chromosomal genes, suggesting that it too was acquired by plasmids from an as-yet-unknown bacterial source.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Pharmacology (medical),Pharmacology
Cited by
344 articles.
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