Molecular Epidemiology and Virulence Characteristics of Klebsiella pneumoniae Strains Isolated from Hospital-Associated Infections

Maria Damian*, 1, Codruta-Romanita Usein1, Andi-Marian Palade1, Stefania Ceciu2, Maria Cosman2
1 Molecular Microbiology Laboratory
2 Bacterial Digestive Infections Laboratory, National Institute of Research- Development for Microbiology and Immunology Cantacuzino, Bucharest, Romania

© 2009Damian et al..

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: ( This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the Molecular Microbiology Laboratory, 2Bacterial Digestive Infections Laboratory, National Institute of Research- Development for Microbiology and Immunology Cantacuzino, Bucharest, Romania; Tel: +4021-5287276; Fax: +4021-5287305; E-mail:



The present study aimed to confirm by classical and molecular laboratory methods hospitalassociated outbreaks due to virulent Klebsiella pneumoniae strains.


Eighty three Klebsiella pneumoniae strains isolated from new-born patients, adults and hospital environment and devices in five hospital units, were analyzed for resistance to antibiotics, including last generation cephalosporins, sensitivity to bacteriophages and pulsed-field gel electrophoresis profiles in order to evaluate the epidemiological relatedness and their clonal spreading. Polymerase chain reaction targeting fur genes and several subtractive sequences (SL 002, SL 003, SL 019, SL 020, SL 021 and SL 025) was used for virulence assessment.


More than 50% of strains were resistant to third generation cephalosporins and among them 69% were extended spectrum beta-lactamase producers. Phage typing associated with pulse field gel electrophoresis documented the clonal dispersion of strains. Studying the distribution of virulence sequence, our results reveal that fur gene is present in all strains and among the subtractive sequences the most frequent is SL 020 followed by SL 019. None of the analyzed sequences are present in all clinical isolates and none of the bacterial strains carry all these sequences pointing out the heterogeneity of Klebsiella pneumoniae population.


Phage typing method associated with pulse field gel electrophoresis typing and genetic profile for virulence indicated the occurrence of hospital associated-infections produced by Klebsiella pneumoniae strains. Moreover, the results reveal that virulence pattern could be used as a molecular marker in order to define strains which are involved in the process of the development of infectious diseases.

Keywords: Klebsiella pneumoniae infections, molecular characterization, PFGE, virulence genes, PCR.