scholarly journals Detection of mutations in parC in quinolone-resistant clinical isolates of Escherichia coli.

1996 ◽  
Vol 40 (2) ◽  
pp. 491-493 ◽  
Author(s):  
J Vila ◽  
J Ruiz ◽  
P Goñi ◽  
M T De Anta
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Quinolone Resistance ◽  
Clinical Isolates ◽  
Serine Residue ◽  
Topoisomerase Iv ◽  
E Coli ◽  
A Subunit ◽  
Detection Of Mutations

The gene parC encodes the A subunit of topoisomerase IV of Escherichia coli. Mutations in the parC region analogous to those in the quinolone resistance-determining region of gyrA were investigated in 27 clinical isolates of E. coli for which ciprofloxacin MICs were 0.0007 to 128 micrograms/ml. Of 15 isolates for which ciprofloxacin MICs were > or = 1 microgram/ml, 8 showed a change in the serine residue at position 80 (Ser-80), 4 showed a change in Glu-84, and 3 showed changes in both amino acids. No mutations were detected in 12 clinical isolates for which ciprofloxacin MICs were < or = 0.25 micrograms/ml. These findings suggest that ParC from E. coli may be another target for quinolones and that mutations at residues Ser-80 and Glu-84 may contribute to decreased fluoroquinolone susceptibility.

scholarly journals Quinolone-resistant mutants of escherichia coli DNA topoisomerase IV parC gene.

1996 ◽  
Vol 40 (3) ◽  
pp. 710-714 ◽  
Author(s):  
Y Kumagai ◽  
J I Kato ◽  
K Hoshino ◽  
T Akasaka ◽  
K Sato ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Dna Gyrase ◽  
Mutant Gene ◽  
Missense Mutations ◽  
Topoisomerase Iv ◽  
Dna Topoisomerase ◽  
E Coli ◽  
A Subunit ◽  
Resistant Strains ◽  
Mutant Genes

Escherichia coli quinolone-resistant strains with mutations of the parC gene, which codes for a subunit of topoisomerase IV, were isolated from a quinolone-resistant gyrA mutant of DNA gyrase. Quinolone-resistant parC mutants were also identified among the quinolone-resistant clinical strains. The parC mutants became susceptible to quinolones by introduction of a parC+ plasmid. Introduction of the multicopy plasmids carrying the quinolone-resistant parC mutant gene resulted in an increase in MICs of quinolones for the parC+ and quinolone-resistant gyrA strain. Nucleotide sequences of the quinolone-resistant parC mutant genes were determined, and missense mutations at position Gly-78, Ser-80, or Glu-84, corresponding to those in the quinolone-resistance-determining region of DNA gyrase, were identified. These results indicate that topoisomerase IV is a target of quinolones in E. coli and suggest that the susceptibility of E. coli cells to quinolones is determined by sensitivity of the targets, DNA gyrase and topoisomerase IV.

scholarly journals Transferable Quinolone Resistance in Vibrio cholerae

2009 ◽  
Vol 54 (2) ◽  
pp. 799-803 ◽  
Author(s):  
Hong Bin Kim ◽  
Minghua Wang ◽  
Sabeena Ahmed ◽  
Chi Hye Park ◽  
Regina C. LaRocque ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Vibrio Cholerae ◽  
Dna Gyrase ◽  
Multidrug Resistant ◽  
Quinolone Resistance ◽  
Topoisomerase Iv ◽  
Dna Topoisomerase ◽  
A Subunit ◽  
Resistant Strains ◽  
Over Time

ABSTRACT Ciprofloxacin was introduced for treatment of patients with cholera in Bangladesh because of resistance to other agents, but its utility has been compromised by the decreasing ciprofloxacin susceptibility of Vibrio cholerae over time. We correlated levels of susceptibility and temporal patterns with the occurrence of mutation in gyrA, which encodes a subunit of DNA gyrase, followed by mutation in parC, which encodes a subunit of DNA topoisomerase IV. We found that ciprofloxacin activity was more recently further compromised in strains containing qnrVC3, which encodes a pentapeptide repeat protein of the Qnr subfamily, members of which protect topoisomerases from quinolone action. We show that qnrVC3 confers transferable low-level quinolone resistance and is present within a member of the SXT integrating conjugative element family found commonly on the chromosomes of multidrug-resistant strains of V. cholerae and on the chromosomes of Escherichia coli transconjugants constructed in the laboratory. Thus, progressive increases in quinolone resistance in V. cholerae are linked to cumulative mutations in quinolone targets and most recently to a qnr gene on a mobile multidrug resistance element, resulting in further challenges for the antimicrobial therapy of cholera.

Involvement of topoisomerase IV and DNA gyrase as ciprofloxacin targets in Streptococcus pneumoniae.

1996 ◽  
Vol 40 (10) ◽  
pp. 2321-2326 ◽  
Author(s):  
X S Pan ◽  
J Ambler ◽  
S Mehtar ◽  
L M Fisher
Keyword(s):  
Streptococcus Pneumoniae ◽  
Dna Gyrase ◽  
Quinolone Resistance ◽  
Clinical Isolates ◽  
Resistant Isolate ◽  
Topoisomerase Iv ◽  
E Coli ◽  
Low Level ◽  
Drug Concentrations ◽  
Level Resistance

Ciprofloxacin-resistant mutants of Streptococcus pneumoniae 7785 were generated by stepwise selection at increasing drug concentrations. Sequence analysis of PCR products from the strains was used to examine the quinolone resistance-determining regions of the GyrA and GyrB proteins of DNA gyrase and the analogous regions of the ParC and ParE subunits of DNA topoisomerase IV. First-step mutants exhibiting low-level resistance had no detectable changes in their topoisomerase quinolone resistance-determining regions, suggesting altered permeation or another novel resistance mechanism. Nine of 10 second-step mutants exhibited an alteration in ParC at Ser-79 to Tyr or Phe or at Ala-84 to Thr. Third- and fourth-step mutants displaying high-level ciprofloxacin resistance were found to have, in addition to the ParC alteration, a change in GyrA at residues equivalent to Escherichia coli GyrA resistance hot spots Ser-83 and Asp-87 or in GyrB at Asp-435 to Asn, equivalent to E. coli Asp-426, part of a highly conserved EGDSA motif in GyrB. No ParE changes were observed. Complementary analysis of two S. pneumoniae clinical isolates displaying low-level resistance to ciprofloxacin revealed a ParC change at Ser-79 to Phe or Arg-95 to Cys but no changes in GyrA, GyrB, or ParE. A highly resistant isolate, in addition to a ParC mutation, had a GyrA alteration at the residue equivalent to E. coli Asp-87. Thus, in both laboratory strains and clinical isolates, ParC mutations preceded those in GyrA, suggesting that topoisomerase IV is a primary topoisomerase target and gyrase is a secondary target for ciprofloxacin in S. pneumoniae.

scholarly journals Emerging Plasmid-Mediated Quinolone Resistance Associated with the qnr Gene in Klebsiella pneumoniae Clinical Isolates in the United States

2004 ◽  
Vol 48 (4) ◽  
pp. 1295-1299 ◽  
Author(s):  
Minggui Wang ◽  
Daniel F. Sahm ◽  
George A. Jacoby ◽  
David C. Hooper
Keyword(s):  
United States ◽  
Escherichia Coli ◽  
Klebsiella Pneumoniae ◽  
Plasmid Dna ◽  
Southern Hybridization ◽  
The United States ◽  
Quinolone Resistance ◽  
Clinical Isolates ◽  
E Coli ◽  
Agarose Gels

ABSTRACT Although quinolone resistance commonly results from chromosomal mutation, recent studies indicate that such resistance can also be transferred on plasmids carrying the gene responsible, qnr. One hundred ten ciprofloxacin-resistant clinical isolates of Klebsiella pneumoniae and Escherichia coli from the United States were screened for the qnr gene by PCR and Southern hybridization of plasmid DNA. Conjugation experiments were done with azide-resistant E. coli J53 as the recipient and selection with azide and sulfonamide, a resistance frequently linked to qnr. EcoRI and BamHI digests of qnr-hybridizing plasmids were subjected to electrophoresis on agarose gels and probed with qnr by Southern hybridization. qnr was detected in 8 (11.1%) of 72 K. pneumoniae strains. These eight positive strains were from six states in the United States. qnr was not found in any of the 38 E. coli strains tested. Quinolone resistance was transferred from seven of the eight probe-positive strains. Transconjugants with qnr-hybridizing plasmids had 32-fold increases in ciprofloxacin MICs relative to E. coli J53. For all eight strains, the sequence of qnr was identical to that originally reported. By size and restriction digests, four plasmids were related to the first-reported plasmid, pMG252, and three were different. Five new qnr plasmids encoded FOX-5 β-lactamase, as did pMG252, but two others produced SHV-7 extended-spectrum β-lactamase. Transferable plasmid-mediated quinolone resistance associated with qnr is now widely distributed in quinolone-resistant clinical strains of K. pneumoniae in the United States. Plasmid-determined quinolone resistance contributes to the increasing quinolone resistance of K. pneumoniae isolates and to the linkage previously observed between resistance to quinolones and the latest β-lactam antibiotics.

scholarly journals Alterations in the GyrA subunit of DNA gyrase and the ParC subunit of topoisomerase IV in quinolone-resistant clinical isolates of Klebsiella pneumoniae.

1997 ◽  
Vol 41 (3) ◽  
pp. 699-701 ◽  
Author(s):  
T Deguchi ◽  
A Fukuoka ◽  
M Yasuda ◽  
M Nakano ◽  
S Ozeki ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Klebsiella Pneumoniae ◽  
Dna Gyrase ◽  
Quinolone Resistance ◽  
Clinical Isolates ◽  
Fluoroquinolone Resistance ◽  
Primary Target ◽  
Gyra Gene ◽  
Topoisomerase Iv ◽  
Complementary Role

We determined a partial sequence of the Klebsiella pneumoniae parC gene, including the region analogous to the quinolone resistance-determining region of the Escherichia coli gyrA gene, and examined 26 clinical strains of K. pneumoniae for an association of alterations in GyrA and ParC with susceptibilities to quinolones. The study suggests that in K. pneumoniae DNA gyrase is a primary target of quinolones and that ParC alterations play a complementary role in the development of higher-level fluoroquinolone resistance.

scholarly journals Quinolone resistance locus nfxD of Escherichia coli is a mutant allele of the parE gene encoding a subunit of topoisomerase IV.

1997 ◽  
Vol 41 (1) ◽  
pp. 175-179 ◽  
Author(s):  
D M Breines ◽  
S Ouabdesselam ◽  
E Y Ng ◽  
J Tankovic ◽  
S Shah ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Mutant Allele ◽  
Quinolone Resistance ◽  
Temperature Sensitive ◽  
Resistance Locus ◽  
Topoisomerase Iv ◽  
Gene Encoding ◽  
Resistance Phenotype ◽  
E Coli ◽  
High Level

The locus nfxD, which contributes to high-level quinolone resistance in Escherichia coli KF111b (gyrAr nfxB nfxD), is only expressed in the presence of a gyrA mutation, and maps to the region of the parC and parE genes, was outcrossed into strain KF130, creating strain DH161 (gyrAr nfxD). DNA sequence analysis of DH161 revealed no changes in the topoisomerase IV parC quinolone resistance-determining region but did identify a single T-to-A mutation in parE at codon 445, leading to a change from Leu to His. Full-length cloned parE+ partially complemented the resistance phenotype in KF111b and DH161, but did not complement the resistance phenotype in strain KF130 (gyrAr). No complementation was seen with cloned, truncated parE+. To confirm these findings, gyrAr was first outcrossed from KF130 into E. coli W3110parE10 [parE temperature sensitive(Ts)] and KL16. The transduced strains KL16 and W3110parE10 were subsequently transformed with plasmids containing cloned parE from DH161 or KL16. Cloned parE from DH161 increased norfloxacin resistance in the parE(Ts) background twofold at 30 degrees C and fourfold at 42 degrees C compared to those for cloned parE from KL16. The same experiment with a non-Ts background revealed a twofold increase in the norfloxacin MIC at both 30 and 42 degrees C. These data identify the nfxD conditional resistance locus as a mutant allele of parE. This report is the first of a quinolone-resistant parE mutant and confirms the role of topoisomerase IV as a secondary target of norfloxacin in E. coli.

scholarly journals Mechanisms Accounting for Fluoroquinolone Resistance in Escherichia coli Clinical Isolates

2008 ◽  
Vol 53 (1) ◽  
pp. 235-241 ◽  
Author(s):  
Sonia K. Morgan-Linnell ◽  
Lauren Becnel Boyd ◽  
David Steffen ◽  
Lynn Zechiedrich
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Agents ◽  
Efflux Pump ◽  
Resistance Mechanisms ◽  
Clinical Isolates ◽  
Fluoroquinolone Resistance ◽  
Multidrug Efflux Pump ◽  
Topoisomerase Iv ◽  
E Coli ◽  
Genes Encoding

ABSTRACT Fluoroquinolone MICs are increased through the acquisition of chromosomal mutations in the genes encoding gyrase (gyrA and gyrB) and topoisomerase IV (parC and parE), increased levels of the multidrug efflux pump AcrAB, and the plasmid-borne genes aac(6′)-Ib-cr and the qnr variants in Escherichia coli. In the accompanying report, we found that ciprofloxacin, gatifloxacin, levofloxacin, and norfloxacin MICs for fluoroquinolone-resistant E. coli clinical isolates were very high and widely varied (L. Becnel Boyd, M. J. Maynard, S. K. Morgan-Linnell, L. B. Horton, R. Sucgang, R. J. Hamill, J. Rojo Jimenez, J. Versalovic, D. Steffen, and L. Zechiedrich, Antimicrob. Agents Chemother. 53:229-234, 2009). Here, we sequenced gyrA, gyrB, parC, and parE; screened for aac(6′)-Ib-cr and qnrA; and quantified AcrA levels in E. coli isolates for which patient sex, age, location, and site of infection were known. We found that (i) all fluoroquinolone-resistant isolates had gyrA mutations; (ii) ∼85% of gyrA mutants also had parC mutations; (iii) the ciprofloxacin and norfloxacin MICs for isolates harboring aac(6′)-Ib-cr (∼23%) were significantly higher, but the gatifloxacin and levofloxacin MICs were not; (iv) no isolate had qnrA; and (v) ∼33% of the fluoroquinolone-resistant isolates had increased AcrA levels. Increased AcrA correlated with nonsusceptibility to the fluoroquinolones but did not correlate with nonsusceptibility to any other antimicrobial agents reported from hospital antibiograms. Known mechanisms accounted for the fluoroquinolone MICs of 50 to 70% of the isolates; the remaining included isolates for which the MICs were up to 1,500-fold higher than expected. Thus, additional, unknown fluoroquinolone resistance mechanisms must be present in some clinical isolates.

scholarly journals Plasmid-Mediated Quinolone Resistance in Clinical Isolates of Escherichia coli from Shanghai, China

2003 ◽  
Vol 47 (7) ◽  
pp. 2242-2248 ◽  
Author(s):  
Minggui Wang ◽  
John H. Tran ◽  
George A. Jacoby ◽  
Yingyuan Zhang ◽  
Fu Wang ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Plasmid Dna ◽  
Bacterial Resistance ◽  
Quinolone Resistance ◽  
Clinical Isolates ◽  
Gene Probe ◽  
E Coli ◽  
Single Nucleotide Change ◽  
Class 1 ◽  
Chromosomal Mutations

ABSTRACT Although quinolone resistance usually results from chromosomal mutations, recent studies indicate that quinolone resistance can also be plasmid mediated. The gene responsible, qnr, is distinct from the known quinolone resistance genes and in previous studies seemed to be restricted to Klebsiella pneumoniae and Escherichia coli isolates from the University of Alabama in Birmingham, where this resistance was discovered. In Shanghai, the frequency of ciprofloxacin resistance in E. coli has exceeded 50% since 1993. Seventy-eight unique ciprofloxacin-resistant clinical isolates of E. coli from Shanghai hospitals were screened for the qnr gene by colony blotting and Southern hybridization of plasmid DNA. Conjugation experiments were done with azide-resistant E. coli J53 as a recipient with selection for plasmid-encoded antimicrobial resistance (chloramphenicol, gentamicin, or tetracycline) and azide counterselection. qnr genes were sequenced, and the structure of the plasmid DNA adjacent to qnr was analyzed by primer walking with a sequential series of outward-facing sequencing primers with plasmid DNA templates purified from transconjugants. Six (7.7%) of 78 strains gave a reproducible hybridization signal with a qnr gene probe on colony blots and yielded strong signals on plasmid DNA preparations. Quinolone resistance was transferred from all six probe-positive strains. Transconjugants had 16- to 250-fold increases in the MICs of ciprofloxacin relative to that of the recipient. All six strains contained qnr with a nucleotide sequence identical to that originally reported, except for a single nucleotide change (CTA→CTG at position 537) encoding the same amino acid. qnr was located in complex In4 family class 1 integrons. Two completely sequenced integrons were designated In36 and In37. Transferable plasmid-mediated quinolone resistance associated with qnr is thus prevalent in quinolone-resistant clinical strains of E. coli from Shanghai and may contribute to the rapid increase in bacterial resistance to quinolones in China.

scholarly journals Cloning and Nucleotide Sequences of the Topoisomerase IV parC and parE Genes ofMycoplasma hominis

1998 ◽  
Vol 42 (8) ◽  
pp. 2024-2031 ◽  
Author(s):  
Cécile M. Bébéar ◽  
Alain Charron ◽  
Joseph Marie Bové ◽  
Christiane Bébéar ◽  
Joel Renaudin
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Staphylococcus Aureus ◽  
Active Site ◽  
Mycoplasma Hominis ◽  
Dna Gyrase ◽  
Quinolone Resistance ◽  
Topoisomerase Iv ◽  
Atp Binding Site ◽  
Gram Positive Bacteria

ABSTRACT The topoisomerase IV parC and parE genes from the wall-less organism Mycoplasma hominis PG21 were cloned and sequenced. The coupled genes are located far from the DNA gyrase genes gyrA and gyrB. They encode proteins of 639 and 866 amino acids, respectively. As expected, the encoded ParE and ParC proteins exhibit higher homologies with the topoisomerase IV subunits of the gram-positive bacteriaStaphylococcus aureus and Streptococcus pneumoniae than with their Escherichia colicounterparts. The conserved regions include the Tyr residue of the active site and the region involved in quinolone resistance (quinolone resistance-determining region [QRDR]) in ParC and the ATP-binding site and the QRDR in ParE.

scholarly journals Smqnr, a New Chromosome-Carried Quinolone Resistance Gene in Stenotrophomonas maltophilia

2008 ◽  
Vol 52 (10) ◽  
pp. 3823-3825 ◽  
Author(s):  
Kenichiro Shimizu ◽  
Ken Kikuchi ◽  
Takashi Sasaki ◽  
Namiko Takahashi ◽  
Masayuki Ohtsuka ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Resistance Gene ◽  
Type Strain ◽  
Stenotrophomonas Maltophilia ◽  
Allelic Diversity ◽  
Quinolone Resistance ◽  
Clinical Isolates ◽  
E Coli

ABSTRACT A new chromosome-carried quinolone resistance gene from Stenotrophomonas maltophilia, Smqnr, was characterized. The gene was present in type strain CCUG 5866 and was also detected in 24 clinical isolates and showed some allelic diversity. The expression of Smqnr in Escherichia coli decreased the susceptibilities of the E. coli isolates to several fluoroquinolones.

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