Attenuated virulence of a Burkholderia cepacia type III secretion mutant in a murine model of infection.
Type III secretion systems are utilized by a number of gram-negative bacterial pathogens to deliver virulence-associated proteins into host cells. Using a PCR-based approach, we identified homologs of type III secretion genes in the gram-negative bacterium Burkholderia cepacia, an important pulmonary pathogen in immunocompromised patients and patients with cystic fibrosis. One of the genes, designated bscN, encodes a member of a family of ATP-binding proteins believed to generate energy driving virulence protein secretion. Genetic dissection of the regions flanking the bscN gene revealed a locus consisting of at least 10 open reading frames, predicted to encode products with significant homology to known type III secretion proteins in other bacteria. A defined null mutation was generated in the bscN gene, and the null strain and wild-type parent strain were examined by use of a murine model of B. cepacia infection. Quantitative bacteriological analysis of the lungs and spleens of infected C57BL/6 mice revealed that the bscN null strain was attenuated in virulence compared to the parent strain, with significantly lower bacterial recovery from the lungs and spleens at 3 days postinfection. Moreover, histopathological changes, including an inflammatory cell infiltrate, were more pronounced in the lungs of mice infected with the wild-type parent strain than in those of mice infected with the isogenic bscN mutant. These results implicate type III secretion as an important determinant in the pathogenesis of B. cepacia.
Tomich
Mladen
M
Department of Microbiology, University of Minnesota, Minneapolis, Minnesota 55455-0312, USA.
Griffith
Adam
A
Herfst
Christine A
CA
Burns
Jane L
JL
Mohr
Christian D
CD
D000818:Animals; D019121:Burkholderia Infections / Q000209:etiology* / Q000473:pathology; D016956:Burkholderia cepacia / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D004269:DNA, Bacterial / Q000032:analysis; D004195:Disease Models, Animal; D008168:Lung / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D009154:Mutation; D014774:Virulence
D004269:DNA, Bacterial