Nonmotility and phagocytic resistance of Pseudomonas aeruginosa isolates from chronically colonized patients with cystic fibrosis

Abstract

Although Pseudomonas aeruginosa chronically colonizes most older patients with cystic fibrosis (CF), bacterial features responsible for its persistence are understood poorly. We observed that many P. aeruginosa isolates from chronically colonized patients were nonmotile and resistant to phagocytosis by macrophages. P. aeruginosa isolates were collected from 20 CF patients for up to 10 years. Isolates from early colonization were highly motile and expressed both flagellin and pilin. However, many isolates from chronically colonized patients lacked flagellin expression and were nonmotile; a total of 1,030 P. aeruginosa CF isolates were examined, of which 39%O were nonmotile. Moreover, sequential isolates recovered from several of the CF patients were consistently nonmotile for up to 10 years. Lack of motility was rare among environmental isolates (1.4%) and other clinical isolates (3.7%) of P. aeruginosa examined. Partial complementation of motility in nonmotile P. aeruginosa isolates was achieved by introduction of extra copies of the rpoN locus carried on plasmid pPT212, indicating that the alternate sigma factor, RpoN, may be involved in the coordinate regulation of virulence factors during CF infection. We hypothesize that the nonmotile phenotype may provide P. aeruginosa a survival advantage in chronic CF infection by enabling it to resist phagocytosis and conserve energy.

Anaerobic culture conditions favor biofilm-like phenotypes inPseudomonas aeruginosaisolates from patients with cystic fibrosis

“…Mature biofilm bacteria are typically slower growing, show increased alginate production and have decreased flagellar-mediated motilities when compared to their planktonic counterparts (Stoodley et al, 2002). These properties have been reported in CF P. aeruginosa isolates from chronic lung infections (Luzar et al, 1985;Mahenthiralingam et al, 1994;Boucher et al, 1997;Sauer et al, 2002).…”

Toll-like receptors in the host defense against Pseudomonas aeruginosa respiratory infection and cystic fibrosis

“…One study compared the efficiency with which human monocytes and macrophages phagocytosed P. aeruginosa mutants and found that motile bacteria were more readily engulfed than those that expressed flagellin but were nonmotile (as a result of mutations of another flagellum component) [62]. In view of this observation, loss of motility, even without a complete loss of the flagellum, may be a mechanism of immune evasion for P. aeruginosa, given that many clinical isolates are nonmotile [63,64]. However, the biological significance of this finding is drawn into question by the results of an in vivo study.…”

Production of N-acyl-?-homoserine lactones by P. aeruginosa isolates from chronic lung infections associated with cystic fibrosis

“…During chronic pulmonary infection of patients with CF P. aeruginosa undergoes phenotypic changes that are thought to represent speci¢c adaptations to the CF lung environment. Strains from chronically colonized patients synthesize vast amounts of the exopolysaccharide alginate, usually lack pili and £agella [7], are de¢cient in O-speci¢c lipopolysaccharides [8], and produce reduced amounts of extracellular virulence factors [9^11]. Since expression of many virulence determinants is quorum sensing controlled we hypothesized that the low amounts of virulence factors observed with isolates from chronically infected patients may be a consequence of reduced levels of AHL synthesis by the strains.…”