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Antimicrobial Agents and Chemotherapy, September 2008, p. 3029-3034, Vol. 52, No. 9
0066-4804/08/$08.00+0 doi:10.1128/AAC.00010-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.
Extended-Spectrum β-Lactamase Production Is Associated with an Increase in Cell Invasion and Expression of Fimbrial Adhesins in Klebsiella pneumoniae
H. Sahly,1,2*
S. Navon-Venezia,3
L. Roesler,4
A. Hay,3
Y. Carmeli,3
R. Podschun,1
C. Hennequin,5
C. Forestier,5 and
I. Ofek6
Institute for Infection Medicine, Faculty of Medicine, University of Kiel, Kiel,1 IPM-Biotech Institute for Immunology, Clinical Pathology and Molecular Medicine, Hamburg, Germany,2 Division of Epidemiology, Tel Aviv Sourasky Medical Center, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel,3 Department of Anaesthesiology and Intensive Care Medicine, University Hospital Schleswig-Holstein, Campus Kiel, Kiel, Germany,4 Laboratoire de Bactériologie, Faculté de Pharmacie, Université de Clermont 1, Clermont-Ferrand, France,5 Department of Human Microbiology, University of Tel Aviv, Tel Aviv, Israel6
Received 3 January 2008/ Returned for modification 5 March 2008/ Accepted 20 May 2008
Extended-spectrum β-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 infection process, so we examined the expression of type 1 and 3 fimbrial adhesins by 58 ESBL-producing and 152 nonproducing isolates of K. pneumoniae and their abilities to invade ileocecal and bladder epithelial cells. Mannose-sensitive hemagglutination of guinea pig erythrocytes and mannose-resistant hemagglutination of ox erythrocytes were evaluated to determine the strains’ abilities to express type 1 and type 3 fimbriae, respectively. Bacterial adhesion to and invasion of epithelial cells were tested by enzyme-linked immunosorbent assay 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, odds ratio [OR] = 2.711, 95% confidence interval [CI] = 1.302 to 5.643 and P = 0.0021, OR = 4.79, 95% CI = 1.587 to 7.627). The mean invasion by ESBL producers (5.5% ± 2.8% and 3.3% ± 2.7%, respectively) was significantly higher than that by non-ESBL producers (2.9% ± 2.6% and 1.8% ± 2%, respectively) (P < 0.0001). Likewise, the proportion of ESBL producers coexpressing 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 to 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 appeared to upregulate the phenotypic expression of one or more genes, resulting in greater invasion ability.
* Corresponding author. Mailing address: IPM-Biotech Institute for Immunology, Clinical Pathology and Molecular Medicine, Lademannbogen 61-63, 22339 Hamburg, Germany. Phone: 00 49 40 53805104. Fax: 00 49 40 53805127. E-mail: sahly{at}labor-lademannbogen.de
Published ahead of print on 23 June 2008.
Antimicrobial Agents and Chemotherapy, September 2008, p. 3029-3034, Vol. 52, No. 9
0066-4804/08/$08.00+0 doi:10.1128/AAC.00010-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.
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