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Infection and Immunity, September 2002, p. 4772-4776, Vol. 70, No. 9
0019-9567/02/$04.00+0     DOI: 10.1128/IAI.70.9.4772-4776.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

Role of the htrA Gene in Klebsiella pneumoniae Virulence

Guadalupe Cortés,1,2 Beatriz de Astorza,1,2 Vicente J. Benedí,2 and Sebastián Albertí1,2*

Unidad de Investigación, Hospital Universitario Son Dureta,1 Área de Microbiología, Departamento de Biología, Universidad de las Islas Baleares and IMEDEA (CSIC-UIB), Palma de Mallorca, Spain2

Received 11 February 2002/ Returned for modification 26 March 2002/ Accepted 10 June 2002

We recently described the use of mini-Tn5 to generate complement-sensitive mutants derived from a complement-resistant Klebsiella pneumoniae clinical isolate deficient in the lipopolysaccharide O side chain. One mutant with a reduced capacity to survive in nonimmune human sera carried the transposon inserted in the htrA gene. We cloned and sequenced the gene and predicted from the deduced amino acid sequence that the putative HtrA homolog contains structural features similar to those of previously described HtrA proteins. To investigate the biological functions and the role of the htrA gene in the virulence of K. pneumoniae, we constructed an isogenic mutant by insertion-duplication mutagenesis. Characterization of the mutant showed that it had greater sensitivity to temperature (50°C) and oxidative stress (H2O2) than the parent strain. Furthermore, the htrA mutant produced less capsule, bound more molecules of complement component C3, and was more sensitive to complement and whole-blood killing than was the parent strain. Finally, disruption of the htrA gene in a virulent K. pneumoniae strain caused a reduction of its virulence in a mice model. Our results indicate that the htrA gene plays an important role in the virulence of K. pneumoniae.

* Corresponding author. Mailing address: Unidad de Investigación, Hospital Son Dureta, Andrea Doria, 55, Palma de Mallorca 07014, Spain. Phone: 34-971-175334. Fax: 34-971-175228. E-mail: salberti{at}hsd.es.

Editor: E. I. Tuomanen

Infection and Immunity, September 2002, p. 4772-4776, Vol. 70, No. 9
0019-9567/02/$04.00+0     DOI: 10.1128/IAI.70.9.4772-4776.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.



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