Type IV Pilus of <b><i>Pseudomonas</i></b><b><i>aeruginosa</i></b> Confers Resistance to Antimicrobial Activities of the Pulmonary Surfactant Protein-A

Abstract

Pseudomonasaeruginosa(PA) is a Gram-negative bacterial pathogen commonly associated with chronic lung infections. Previously, we have identified several PA virulence factors that are important for resistance to the surfactant protein-A (SP-A), a pulmonary innate immunity protein that mediates bacterial opsonization and membrane permeabilization. In this study, we demonstrate that the type IV pilus (Tfp) is important in the resistance of PA to the antibacterial effects of SP-A. The Tfp-deficient mutant ΔpilA is severely attenuated in an acute pneumonia model of infection in the lungs of wild-type mice, but is virulent in the lungs of SP-A^-/- mice. The ΔpilA bacteria are more susceptible to SP-A-mediated aggregation and opsonization. In addition, the integrity of the outer membranes of ΔpilA bacteria is compromised, rendering them more susceptible to SP-A-mediated membrane permeabilization. By comparing Tfp extension and retraction mutants, we demonstrate that the increased susceptibility of ΔpilA to SP-A-mediated opsonization requires the total absence of Tfp from PA cells. Finally, we provide evidence of increased expression of nonpilus adhesin OprH that may serve as an SP-A ligand, resulting in increased phagocytosis and preferential pulmonary clearance of ΔpilA.

Mutations in the β-Subunit of the RNA Polymerase Impair the Surface-Associated Motility and Virulence of Acinetobacter baumannii

“…(27). Motility is also associated with enhanced antibiotic resistance (28), protection against host macrophages (29), and the first stage of biofilm generation (30).…”

Type IV Pilus Glycosylation Mediates Resistance of Pseudomonas aeruginosa to Opsonic Activities of the Pulmonary Surfactant Protein A

“…SP-A ϩ/ϩ and SP-A Ϫ/Ϫ mice (groups of 10) were given a single intranasal inoculation of 3 ϫ 10 6 CFU of the parental clinical strain 1244 or the ⌬tfpO mutant. After 18 h, mouse lungs were harvested for histology (n ϭ 3) or bacterial enumeration (n ϭ 7) as previously described (22,24). For mortality studies, animals (n ϭ 10) were monitored for up to 48 h. Moribund animals that displayed rough hair coat, hunched posture, distended abdomen, lethargy, or inability to eat or drink were euthanized and counted as dead.…”

“…The phagocytosis rates between different P. aeruginosa strains were compared using a modified gentamicin exclusion assay as previously described (22,24). Briefly, C3H/HeN and C3H SP-A Ϫ/Ϫ mice (n ϭ 3) were given a single intranasal inoculation of 10 7 CFU of 1244 or ⌬tfpO strain.…”

“…As discussed above, SP-A mediates its antimicrobial effects by enhancing microbial clearance through membrane permeabilization and opsonization (22,24,(28)(29)(30)(31)(32). To further examine whether O-glycosylation of P. aeruginosa Tfp with O-ag increases the resistance to SP-A-mediated membrane permeability, we measured the amounts of leaked thiol containing proteins from 1244 versus ⌬tfpO mutant after exposure to hSP-A.…”

“…Most recently, we have demonstrated that Tfp of P. aeruginosa mediates resistance to antibacterial effects of pulmonary surfactant protein A (SP-A), an important innate immunity protein that induces opsonization and membrane permeability in microbes (22). Despite reports showing frequent association of P. aeruginosa strains in the TfpO-expressing group I alleles with CF and the importance of TfpO-mediated glycosylation as a virulence factor in mouse lung infection (10,11), the molecular basis behind the importance of Tfp glycosylation in P. aeruginosa pathogenesis, especially in the context of alveolar epithelium, is not fully understood.…”