Involvement of pmrAB and phoPQ in polymyxin B adaptation and inducible resistance in non-cystic fibrosis clinical isolates of Pseudomonas aeruginosa
| Autor: | Jorge Luiz Mello Sampaio, S I Sinto, Carlos R.V. Kiffer, Kristen N. Schurek, Robert E. W. Hancock, Caio M. F. Mendes |
|---|---|
| Rok vydání: | 2009 |
| Předmět: |
Membrane permeability
Cystic Fibrosis Genotype Operon medicine.drug_class Polymyxin Microbial Sensitivity Tests medicine.disease_cause Microbiology Bacterial Proteins Mechanisms of Resistance Drug Resistance Multiple Bacterial medicine Pharmacology (medical) Promoter Regions Genetic Antibacterial agent Polymyxin B Pharmacology biology Pseudomonas aeruginosa biology.organism_classification Anti-Bacterial Agents Infectious Diseases lipids (amino acids peptides and proteins) Bacterial outer membrane Pseudomonadaceae medicine.drug Transcription Factors |
| Zdroj: | Antimicrobial agents and chemotherapy. 53(10) |
| ISSN: | 1098-6596 |
| Popis: | During investigation of susceptibility testing methods for polymyxins, 24 multidrug-resistant clinical isolates of Pseudomonas aeruginosa were observed to have a distinct, reproducible phenotype in which skipped wells were observed during broth microdilution testing for polymyxin B. Possible mechanisms underlying this phenotype were investigated. The effects of various concentrations of polymyxin B on growth, the expression of resistance genes, and outer-membrane permeability were observed. Real-time PCR was performed to compare the expression, in response to selected concentrations of polymyxin B, of genes related to the PhoP-PhoQ and PmrA-PmrB two-component regulatory systems in polymyxin B-susceptible isolate PAO1, polymyxin B-resistant isolate 9BR, and two isolates (19BR and 213BR) exhibiting the skipped-well phenotype. 19BR and 213BR appeared to have similar basal levels of expression compared to that of PAO1 for phoQ , arnB , and PA4773 (from the pmrAB operon), and in contrast, 9BR had 52- and 280-fold higher expression of arnB and PA4773, respectively. The expression of arnB and PA4773 increased in response to polymyxin B in a concentration-dependent manner for 9BR but not for 19BR and 213BR. For these isolates, expression was significantly increased for arnB and PA4773, as well as phoQ , only upon exposure to 2 μg/ml polymyxin B but not at a lower concentration of 0.125 μg/ml. The sequencing of the pmrAB and phoPQ operons for all three isolates revealed a number of unique mutations compared to that for PAO1. 1- N -phenylnaphthylamine (NPN) was used to study the effect of preincubation with polymyxin B on the self-promoted uptake of polymyxin B across the outer membrane. The preincubation of cells with 2 μg/ml polymyxin B affected baseline membrane permeability in 19BR and 213BR and also resulted in a reduced rate of NPN uptake in these isolates and in PAO1 but not in 9BR. The results presented here suggest that the skipped-well isolates have the ability to adapt to specific concentrations of polymyxin B, inducing known polymyxin B resistance genes involved in generating alterations in the outer membrane. |
| Databáze: | OpenAIRE |
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