Attenuated Virulence of a Burkholderia cepacia Type III Secretion Mutant in a Murine Model of Infection

Abstract

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.

Attenuated virulence and protective efficacy of a Burkholderia pseudomallei bsa type III secretion mutant in murine models of melioidosis

“…B. pseudomallei contains two other putative type III secretion loci, which are similar to the hrp gene cluster of Ralstonia solanacearum and TTSS loci in other plant pathogens (Winstanley et al, 1999;Rainbow et al, 2002); the role played by these systems in virulence awaits investigation. A mutation in the plant pathogen-like type III secretion apparatus of Burkholderia cepacia genomovar III was recently reported to be attenuating in a murine model of respiratory infection (Tomich et al, 2003). Thus TTSSs appear to play key roles in the pathogenesis of Burkholderia infections in animals.…”

Burkholderia xenovorans LB400 harbors a multi-replicon, 9.73-Mbp genome shaped for versatility

“…However, in common with other Burkholderia genomes (20), LB400 possesses multiple hemagglutinin-like adhesin genes (n ϭ 9), suggesting that binding to microbial and eukaryotic cells is important to its lifestyle. LB400 also possesses one type III secretion system (20,52,53). We found potential virulence-related functions only present on islands 9, 11, and 4 (type IV secretion and adhesion functions; Table 4), suggesting that laterally acquired DNA has been retained by LB400 by selection in the natural environment rather than during primary infection.…”

Genome-wide analysis of DNA repeats in Burkholderia cenocepacia J2315 identifies a novel adhesin-like gene unique to epidemic-associated strains of the ET-12 lineage

“…They have the capacity of spreading between patients and lead determined (Holden et al, 2009). Although the pathogenesis of Bcc is not well understood, a few virulence factors, such as two quorum-sensing systems (Sokol et al, 2003), iron acquisition via siderophore production (Visser et al, 2004), exopolysaccharide synthesis (Moreira et al, 2003) and a type III secretion system (Tomich et al, 2003), have been identified.…”