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Antimicrob. Agents Chemother. doi:10.1128/AAC.00010-08
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

ESBL-production is associated with an increase of cell invasion and fimbrial adhesins' expression in Klebsiella pneumoniae

Institute for Infection Medicine, Faculty of Medicine, University of Kiel, Kiel; Institute of Immunology, Clinical Pathology and Molecular Medicine, Biotech, Hamburg, Germany; Division of Epidemiology, Tel-Aviv Sourasky Medical Center, Sackler School of Medicine, Tel-Aviv University, Israel; Department of Anaesthesiology and Intensive Care Medicine, University Hospital Schleswig-Holstein, Campus Kiel, Germany; Laboratoire de Bactériologie, Faculté de Pharmacie, Université de Clermont 1, Clermont-Ferrand, France; Department of Human Microbiology, University of Tel Aviv, Israel

^* To whom correspondence should be addressed. Email: sahly{at}labor-lademannbogen.de.

	Abstract

Extended-Spectrum--lactamase- (ESBL) producing Klebsiella pneumoniae strains are suggested to possess higher pathogenic potential than non-ESBL-producers. Microbial adherence to and invasion of host cells are critical steps in the infectious process so we examined the expression of type-1 and 3 fimbrial adhesins by 58 ESBL-producing and 152 non-producing isolates of K. pneumoniae and their ability to invade ileocecal and bladder epithelial cells. Mannose-sensitive haemagglutination of guinea pig erythrocytes and mannose-resistant haemagglutination of ox erythrocytes were evaluated for determining the strains' ability to express type-1 and type-3 fimbriae, respectively. Bacterial adhesion to and invasion of epithelial cells were tested by ELISA and imipenem killing assay, respectively.

The adherence of ESBL and non-ESBL-producing strains to epithelial cells did not differ significantly (p>0.05). In contrast, the proportion of strains capable of invading (>5% relative invasion) ileocecal and bladder epithelial cells was significantly higher among ESBL-producers (81%, n=47/58, and 27.6%, n=16/58, respectively) than among non-ESBL-producers (61%, n=93/152, and 10%, n=15/152, respectively) (p=0.0084; OR=2.711; 95% CI=1.302-5.643 and p=0.0021; OR=4.79; 95% CI 1.587-7.627); The mean invasion by ESBL-producer (5.5±2.8% and 3.3±2.7%, respectively) was significantly higher than by non-ESBL-producers (2.9±2.6% and 1.8±2%, respectively) (p<0.0001). Likewise, the proportion of ESBL-producers co-expressing both fimbrial adhesins was significantly higher (79.3%, n=46/58) than that of non-ESBL-producers (61.8%, n=94/152) (p=0.0214; OR=2,365; 95% CI=1.157-4.834). Upon acquisition of SHV-12 encoding plasmids two transconjugants switched on to produce type-3 fimbriae while expression of type-1 fimbriae was not affected. The acquisition of an ESBL-plasmid appears to upregulate the phenotypic expression of one or more genes resulting in higher invasion ability.