Role of the AcrAB efflux pump in Klebsiella pneumoniae respiratory infections

Abstract number: O241

Padilla E., Doménech-Sánchez A., Campos M.A., Martínez-Martínez L., Bengoechea J.A., Alberti S.

Background: AcrAB efflux pump activity is critical to mediate antimicrobial resistance in K. pneumoniae. However, the role of this efflux pump in the virulence of this opportunistic pathogen has been poorly investigated.

Objective: The aim of this study was to investigate the role of the AcrAB efflux pump of K. pneumoniae in the respiratory infections caused by this microorganism.

Methods: We constructed by insertion-duplication mutagenesis a specific AcrB mutant, designed as 52DB, from the K. pneumoniae virulent strain 52145. Characterisation of the mutant was performed by Southern blot analysis, RT-PCR analysis of AcrB expression, and determination of the MIC of several antimicrobial agents.

To investigate the virulence of the AcrB-deficient mutant, standard survival assays were performed incubating the bacterial cells with human bronchoalveolar lavage, polymyxin B or human beta-defensin. Virulence was also tested in a murine model of pneumonia.

Results: Southern blot and RT-PCR analysis confirmed the interruption of the AcrB gene and the abolishment of the expression of AcrB in 52DB. The mutant was more susceptible to cefoxitin, erythromycin, and nalidixic acid than the parent strain. MICs (mg/l) of antibiotics for strain 52145 and its 52DB mutant were respectively; 8 and 1 (cefoxitin), 64 and 1 (erythromycin), and 4 and 0.5 (nalidixic acid).

The mutant 52DB exhibited a significant reduction of more than three-folds in its capacity to survive in the presence of bronchoalveolar lavage, polymixin or human beta-defensin compared with the parent strain. Furthermore, the mutant was less virulent than the parent strain in a murine model of pneumonia.

Conclusions: AcrAB efflux pump contributes to both antimicrobial resistance and virulence of K. pneumoniae.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Location: Barcelona, Spain
Presentation type:
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