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Journal of Clinical Microbiology, June 2004, p. 2701-2706, Vol. 42, No. 6
0095-1137/04/$08.00+0     DOI: 10.1128/JCM.42.6.2701-2706.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Detection and Prevalence of Active Drug Efflux Mechanism in Various Multidrug-Resistant Klebsiella pneumoniae Strains from Turkey

Department of Microbiology, School of Medicine, Marmara University, Istanbul, Turkey,¹ Enveloppe Bactérienne, Perméabilité et Antibiotiques, EA 2197, IFR48, Faculté de Médecine, Université de la Mediterranée, Marseille,² Service de Bactériologie-Virologie, Hôpital de Bicêtre, Faculté de Médecine Paris Sud, Université Paris XI, Le Kremlin-Bicêtre, France³

Received 29 October 2003/ Returned for modification 7 January 2004/ Accepted 13 February 2004

The prevalence of active drug efflux pump and porin alterations was investigated in Turkish nosocomial strains of Klebsiella pneumoniae exhibiting a multidrug-resistant phenotype. MICs of various antibiotics, including quinolones, chloramphenicol, tetracycline, and ß-lactams, for those strains were determined either with or without the efflux pump inhibitor phenylalanine arginine ß-naphthylamide (PAßN). Thirty-nine percent of the strains exhibited a PAßN-modulated resistance for quinolones, chloramphenicol, and tetracycline. In these strains, a significant increase of chloramphenicol accumulation was gained in the presence of the efflux pump inhibitor PAßN or with the energy uncoupler carbonyl cyanide m-chlorophenylhydrazone. Moreover, high-level expression of the membrane fusion protein AcrA, which was immunodetected in most of those isolates, suggests that the AcrAB/TolC efflux machinery contributed to their antibiotic resistance. Studies of K. pneumoniae porins indicated that the majority of the strains, including extended-spectrum ß-lactamase producers and efflux-positive ones, presented an alteration in their sorbitol-sensitive porin (OmpK35) expression. This is the first report showing the prominent role of active drug efflux in the antibiotic resistance of nosocomial K. pneumoniae strains from Turkey.

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