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Plasmid-mediated quinolone resistance determinants among Gram-negative bacteraemia isolates: a hidden threat
- Source :
- Journal of medical microbiology. 66(3)
- Publication Year :
- 2016
-
Abstract
- Purpose. The aim of the study was to investigate the prevalence of plasmid-mediated quinolone resistance (PMQR) genes in an unselected collection of bloodstream isolates recovered over an 18-month period in a laboratory affiliated to a university hospital in Athens, Greece, and to assess their impact on the in vitro activity of ciprofloxacin and levofloxacin. Methods. Eight PMQR genes were screened by PCR and sequencing. All PMQR-positive isolates were submitted to isoelectric focusing for β-lactamase detection, conjugation or transformation, time-kill assays, mutant prevention concentrationand inoculum effect evaluation. PCR and sequencing of gyrA and parC were performed for detection of chromosomal mutations. Results. Among 96 Gram-negative isolates, 7 (7.3 %) carried one or more PMQR genes. qnrS1 was the most prevalent (5.2 %), followed by aac(6′ )-Ib-cr (4.2 %) and their combination (2 %). Cloning was successful for three isolates. The presence of a single PMQR determinant without any target modification was not associated with quinolone resistance with one exception, S tenotrophomonas maltophilia carrying qnrS1, which was resistant to norfloxacin and ciprofloxacin, but in this isolate, additional mechanisms of quinolone resistance cannot be excluded. All PMQR-positive isolates showed a significant inoculum effect. The mutant prevention concentrations of ciprofloxacin against the quinolone-susceptible clinical isolates ranged from 0.38 to 32 mg l−1 and those of levofloxacin from 1 to 32 mg l−1. Conclusions. PMQRs compromised the bactericidal activity of ciprofloxacin and levofloxacin when expressed in Enterobacter cloacae, S. maltophilia or Klebsiella pneumoniae and when more than one co-existed. PMQR determinants represent an unrecognized threat, capable to compromise the in vitro activity of quinolones if expressed in a favourable genetic environment and to favour selection of resistant mutants by widening the mutant selection window of these agents.
- Subjects :
- 0301 basic medicine
Microbiology (medical)
DNA Topoisomerase IV
medicine.drug_class
Klebsiella pneumoniae
R Factors
Stenotrophomonas maltophilia
030106 microbiology
Antibiotics
Bacteremia
Drug resistance
Levofloxacin
Microbial Sensitivity Tests
Quinolones
Microbiology
beta-Lactamases
03 medical and health sciences
Plasmid
Enterobacteriaceae
Ciprofloxacin
Drug Resistance, Bacterial
medicine
Escherichia coli
Humans
Norfloxacin
biology
Greece
Enterobacteriaceae Infections
General Medicine
biochemical phenomena, metabolism, and nutrition
bacterial infections and mycoses
biology.organism_classification
Anti-Bacterial Agents
DNA Gyrase
Mutation
Gram-Negative Bacterial Infections
Enterobacter cloacae
medicine.drug
Subjects
Details
- ISSN :
- 14735644
- Volume :
- 66
- Issue :
- 3
- Database :
- OpenAIRE
- Journal :
- Journal of medical microbiology
- Accession number :
- edsair.doi.dedup.....2996247afdf34bededa307a5f3489f18