Multiple genotypic changes in hypersusceptible strains of Pseudomonas aeruginosa isolated from cystic fibrosis patients do not always correlate with the phenotype

Daniel J. Wolter, Jennifer A. Black, Philip D. Lister, Nancy D. Hanson

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

Objectives: Although Pseudomonas aeruginosa from cystic fibrosis patients are well known for their antibiotic resistance, isolates that are highly susceptible to multiple drug classes have also been encountered. In this study, hypersusceptible P. aeruginosa isolates were analysed for changes in intrinsic resistance mechanisms to explain the observed phenotype. Methods: P. aeruginosa strains PA30 and PA431 were isolated from the sputa of cystic fibrosis patients and susceptibilities were determined by agar dilution. Isolates were genetically unrelated by PFGE analysis. Expression of efflux pumps, porins, a chromosomal cephalosporinase and a gene, glmS, previously implicated in hypersusceptibility were evaluated by real-time RT-PCR, outer membrane protein analysis and β-lactamase hydrolysis assays. Results: PA30 was hypersusceptible to β-lactams, fluoroquinolones and antimetabolites, with MICs at least 4-fold lower than those for the prototype strain PAO1, while PA431 was hypersusceptible to β-lactams and antimetabolites. Both isolates overproduced the porin OprF but showed down-regulation in the production of the carbapenem channel OprD despite carbapenem hypersusceptibility. PA30 had decreased expression of the mexAB - oprM pump involved with intrinsic antibiotic resistance but overexpressed the mexCD - oprJ and mexEF - oprN efflux systems normally associated with acquired resistance. PA431 showed down-regulation of oprM, the last gene in the mexAB - oprM operon, but overexpressed the mexXY pump. The ampC β-lactamase was weakly inducible in strain PA30, corresponding to cefoxitin hypersusceptibility. Conclusions: The changes in expression of several intrinsic mechanisms in the hypersusceptible strains did not correlate with the observed phenotype. These data highlight the complex interactions of resistance mechanisms in P. aeruginosa and their roles in drug susceptibility.

Original languageEnglish
Pages (from-to)294-300
Number of pages7
JournalJournal of Antimicrobial Chemotherapy
Volume64
Issue number2
DOIs
StatePublished - 2009

Fingerprint

Cystic Fibrosis
Pseudomonas aeruginosa
Phenotype
Antimetabolites
Lactams
Porins
Carbapenems
Microbial Drug Resistance
Down-Regulation
Cephalosporinase
Cefoxitin
Fluoroquinolones
Operon
Sputum
Pharmaceutical Preparations
Genes
Agar
Real-Time Polymerase Chain Reaction
Membrane Proteins
Hydrolysis

All Science Journal Classification (ASJC) codes

  • Pharmacology
  • Pharmacology (medical)
  • Infectious Diseases

Cite this

Multiple genotypic changes in hypersusceptible strains of Pseudomonas aeruginosa isolated from cystic fibrosis patients do not always correlate with the phenotype. / Wolter, Daniel J.; Black, Jennifer A.; Lister, Philip D.; Hanson, Nancy D.

In: Journal of Antimicrobial Chemotherapy, Vol. 64, No. 2, 2009, p. 294-300.

Research output: Contribution to journalArticle

@article{64048e2fce0644bc89e9381941d238a6,
title = "Multiple genotypic changes in hypersusceptible strains of Pseudomonas aeruginosa isolated from cystic fibrosis patients do not always correlate with the phenotype",
abstract = "Objectives: Although Pseudomonas aeruginosa from cystic fibrosis patients are well known for their antibiotic resistance, isolates that are highly susceptible to multiple drug classes have also been encountered. In this study, hypersusceptible P. aeruginosa isolates were analysed for changes in intrinsic resistance mechanisms to explain the observed phenotype. Methods: P. aeruginosa strains PA30 and PA431 were isolated from the sputa of cystic fibrosis patients and susceptibilities were determined by agar dilution. Isolates were genetically unrelated by PFGE analysis. Expression of efflux pumps, porins, a chromosomal cephalosporinase and a gene, glmS, previously implicated in hypersusceptibility were evaluated by real-time RT-PCR, outer membrane protein analysis and β-lactamase hydrolysis assays. Results: PA30 was hypersusceptible to β-lactams, fluoroquinolones and antimetabolites, with MICs at least 4-fold lower than those for the prototype strain PAO1, while PA431 was hypersusceptible to β-lactams and antimetabolites. Both isolates overproduced the porin OprF but showed down-regulation in the production of the carbapenem channel OprD despite carbapenem hypersusceptibility. PA30 had decreased expression of the mexAB - oprM pump involved with intrinsic antibiotic resistance but overexpressed the mexCD - oprJ and mexEF - oprN efflux systems normally associated with acquired resistance. PA431 showed down-regulation of oprM, the last gene in the mexAB - oprM operon, but overexpressed the mexXY pump. The ampC β-lactamase was weakly inducible in strain PA30, corresponding to cefoxitin hypersusceptibility. Conclusions: The changes in expression of several intrinsic mechanisms in the hypersusceptible strains did not correlate with the observed phenotype. These data highlight the complex interactions of resistance mechanisms in P. aeruginosa and their roles in drug susceptibility.",
author = "Wolter, {Daniel J.} and Black, {Jennifer A.} and Lister, {Philip D.} and Hanson, {Nancy D.}",
year = "2009",
doi = "10.1093/jac/dkp185",
language = "English",
volume = "64",
pages = "294--300",
journal = "Journal of Antimicrobial Chemotherapy",
issn = "0305-7453",
publisher = "Oxford University Press",
number = "2",

}

TY - JOUR

T1 - Multiple genotypic changes in hypersusceptible strains of Pseudomonas aeruginosa isolated from cystic fibrosis patients do not always correlate with the phenotype

AU - Wolter, Daniel J.

AU - Black, Jennifer A.

AU - Lister, Philip D.

AU - Hanson, Nancy D.

PY - 2009

Y1 - 2009

N2 - Objectives: Although Pseudomonas aeruginosa from cystic fibrosis patients are well known for their antibiotic resistance, isolates that are highly susceptible to multiple drug classes have also been encountered. In this study, hypersusceptible P. aeruginosa isolates were analysed for changes in intrinsic resistance mechanisms to explain the observed phenotype. Methods: P. aeruginosa strains PA30 and PA431 were isolated from the sputa of cystic fibrosis patients and susceptibilities were determined by agar dilution. Isolates were genetically unrelated by PFGE analysis. Expression of efflux pumps, porins, a chromosomal cephalosporinase and a gene, glmS, previously implicated in hypersusceptibility were evaluated by real-time RT-PCR, outer membrane protein analysis and β-lactamase hydrolysis assays. Results: PA30 was hypersusceptible to β-lactams, fluoroquinolones and antimetabolites, with MICs at least 4-fold lower than those for the prototype strain PAO1, while PA431 was hypersusceptible to β-lactams and antimetabolites. Both isolates overproduced the porin OprF but showed down-regulation in the production of the carbapenem channel OprD despite carbapenem hypersusceptibility. PA30 had decreased expression of the mexAB - oprM pump involved with intrinsic antibiotic resistance but overexpressed the mexCD - oprJ and mexEF - oprN efflux systems normally associated with acquired resistance. PA431 showed down-regulation of oprM, the last gene in the mexAB - oprM operon, but overexpressed the mexXY pump. The ampC β-lactamase was weakly inducible in strain PA30, corresponding to cefoxitin hypersusceptibility. Conclusions: The changes in expression of several intrinsic mechanisms in the hypersusceptible strains did not correlate with the observed phenotype. These data highlight the complex interactions of resistance mechanisms in P. aeruginosa and their roles in drug susceptibility.

AB - Objectives: Although Pseudomonas aeruginosa from cystic fibrosis patients are well known for their antibiotic resistance, isolates that are highly susceptible to multiple drug classes have also been encountered. In this study, hypersusceptible P. aeruginosa isolates were analysed for changes in intrinsic resistance mechanisms to explain the observed phenotype. Methods: P. aeruginosa strains PA30 and PA431 were isolated from the sputa of cystic fibrosis patients and susceptibilities were determined by agar dilution. Isolates were genetically unrelated by PFGE analysis. Expression of efflux pumps, porins, a chromosomal cephalosporinase and a gene, glmS, previously implicated in hypersusceptibility were evaluated by real-time RT-PCR, outer membrane protein analysis and β-lactamase hydrolysis assays. Results: PA30 was hypersusceptible to β-lactams, fluoroquinolones and antimetabolites, with MICs at least 4-fold lower than those for the prototype strain PAO1, while PA431 was hypersusceptible to β-lactams and antimetabolites. Both isolates overproduced the porin OprF but showed down-regulation in the production of the carbapenem channel OprD despite carbapenem hypersusceptibility. PA30 had decreased expression of the mexAB - oprM pump involved with intrinsic antibiotic resistance but overexpressed the mexCD - oprJ and mexEF - oprN efflux systems normally associated with acquired resistance. PA431 showed down-regulation of oprM, the last gene in the mexAB - oprM operon, but overexpressed the mexXY pump. The ampC β-lactamase was weakly inducible in strain PA30, corresponding to cefoxitin hypersusceptibility. Conclusions: The changes in expression of several intrinsic mechanisms in the hypersusceptible strains did not correlate with the observed phenotype. These data highlight the complex interactions of resistance mechanisms in P. aeruginosa and their roles in drug susceptibility.

UR - http://www.scopus.com/inward/record.url?scp=67650711671&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=67650711671&partnerID=8YFLogxK

U2 - 10.1093/jac/dkp185

DO - 10.1093/jac/dkp185

M3 - Article

VL - 64

SP - 294

EP - 300

JO - Journal of Antimicrobial Chemotherapy

JF - Journal of Antimicrobial Chemotherapy

SN - 0305-7453

IS - 2

ER -