1: J Antimicrob Chemother. 2007 Mar;59(3):378-86. Epub 2007 Feb 8.

A combined phenotypic and genotypic method for the detection of Mex efflux pumps
in Pseudomonas aeruginosa.

Mesaros N, Glupczynski Y, Avrain L, Caceres NE, Tulkens PM, Van Bambeke F.

Unite de Pharmacologie cellulaire et moleculaire, Brussels, Universite
catholique de Louvain, UCL 7370 avenue E. Mounier 73, B-1200 Bruxelles, Belgium.

Background Mex efflux pumps contribute to multidrug resistance in Pseudomonas
aeruginosa. Evidencing their expression in clinical isolates would help in
rationalizing antibiotic selection. Methods We have developed a combined
phenotypic and genotypic approach for the differential diagnosis of resistance
mediated by four major transporters (MexAB-OprM, MexCD-OprJ, MexEF-OprN,
MexXY-OprM). The methodology was validated using reference strains harbouring
only one specific transporter and its applicability evaluated towards seven
selected clinical isolates, the resistance mechanisms of which could not be
assigned by conventional techniques. Phenotypic detection used MIC measurements
with reporter antibiotics [carbenicillin (MexAB-OprM); erythromycin
(MexCD-OprJ); norfloxacin and imipenem (MexEF-OprN); gentamicin (MexXY-OprM)]
with and without Phe-Arg-beta-naphthylamide. Genotypic detection was made by
semi-quantitative reverse transcription PCR (RT-PCR) for mexC and mexE, and by
quantitative competitive RT-PCR and real-time PCR for mexA and mexX (correlation
between both methods: > 88 % ; overexpression levels ranging between 4.8 and
8.1). Results Convergence between phenotypic and genotypic methods was observed
in control strains for all pumps. For clinical isolates, convergence was
obtained in 6 of 7 strains for MexXY-OprM and MexEF-OprM, and in 5 of 7 for
MexAB-OprM and MexCD-OprJ, mostly due to hard to interpret phenotypic data.
Conclusions The data plead for combining phenotypic and genotypic approaches in
the diagnosis of efflux-mediated resistance in P. aeruginosa.

PMID: 17289770 [PubMed - in process]

Related Links

    Influence of the MexA-MexB-oprM multidrug efflux system on expression of the
MexC-MexD-oprJ and MexE-MexF-oprN multidrug efflux systems in Pseudomonas
aeruginosa. [J Antimicrob Chemother. 2000] PMID:11102405
    Expression of Pseudomonas aeruginosa multidrug efflux pumps MexA-MexB-OprM
and MexC-MexD-OprJ in a multidrug-sensitive Escherichia coli strain. [Antimicrob
Agents Chemother. 1998] PMID:9449262
    Overexpression of the multidrug efflux pumps MexCD-OprJ and MexEF-OprN is
associated with a reduction of type III secretion in Pseudomonas aeruginosa. [J
Bacteriol. 2005] PMID:15687203
    Multidrug efflux pumps: expression patterns and contribution to antibiotic
resistance in Pseudomonas aeruginosa biofilms. [Antimicrob Agents Chemother.
2001] PMID:11353623
    Efflux-mediated resistance to tigecycline (GAR-936) in Pseudomonas
aeruginosa PAO1. [Antimicrob Agents Chemother. 2003] PMID:12604529