Pseudomonas aeruginosa in vitro phenotypes distinguish cystic fibrosis infection stages and outcomes.

RATIONALE: Pseudomonas aeruginosa undergoes phenotypic changes during cystic fibrosis (CF) lung infection. Although mucoidy is traditionally associated with transition to chronic infection, we hypothesized that additional in vitro phenotypes correlate with this transition and contribute to disease. OBJECTIVES: To characterize the relationships between in vitro P. aeruginosa phenotypes, infection stage, and clinical outcomes. METHODS: A total of 649 children with CF and newly identified P. aeruginosa were followed for a median 5.4 years during which a total of 2,594 P. aeruginosa isolates were collected. Twenty-six in vitro bacterial phenotypes were assessed among the isolates, including measures of motility, exoproduct production, colony morphology, growth, and metabolism. MEASUREMENTS AND MAIN RESULTS: P. aeruginosa phenotypes present at the time of culture were associated with both stage of infection (new onset, intermittent, or chronic) and the primary clinical outcome, occurrence of a pulmonary exacerbation (PE) in the subsequent 2 years. Two in vitro P. aeruginosa phenotypes best distinguished infection stages: pyoverdine production (31% of new-onset cultures, 48% of intermittent, 69% of chronic) and reduced protease production (31%, 39%, and 65%, respectively). The best P. aeruginosa phenotypic predictors of subsequent occurrence of a PE were mucoidy (odds ratio, 1.75; 95% confidence interval, 1.19-2.57) and reduced twitching motility (odds ratio, 1.43; 95% confidence interval, 1.11-1.84). CONCLUSIONS: In this large epidemiologic study of CF P. aeruginosa adaptation, P. aeruginosa isolates exhibited two in vitro phenotypes that best distinguished early and later infection stages. Among the many phenotypes tested, mucoidy and reduced twitching best predicted subsequent PE. These phenotypes indicate potentially useful prognostic markers of transition to chronic infection and advancing lung disease.

Pseudomonas aeruginosa phenotypes associated with eradication failure in children with cystic fibrosis.

BACKGROUND: Pseudomonas aeruginosa is a key respiratory pathogen in people with cystic fibrosis (CF). Due to its association with lung disease progression, initial detection of P. aeruginosa in CF respiratory cultures usually results in antibiotic treatment with the goal of eradication. Pseudomonas aeruginosa exhibits many different phenotypes in vitro that could serve as useful prognostic markers, but the relative relationships between these phenotypes and failure to eradicate P. aeruginosa have not been well characterized. METHODS: We measured 22 easily assayed in vitro phenotypes among the baseline P. aeruginosa isolates collected from 194 participants in the 18-month EPIC clinical trial, which assessed outcomes after antibiotic eradication therapy for newly identified P. aeruginosa. We then evaluated the associations between these baseline isolate phenotypes and subsequent outcomes during the trial, including failure to eradicate after antipseudomonal therapy, emergence of mucoidy, and occurrence of an exacerbation. RESULTS: Baseline P. aeruginosa isolates frequently exhibited phenotypes thought to represent chronic adaptation, including mucoidy. Wrinkly colony surface and irregular colony edges were both associated with increased risk of eradication failure (hazard ratios [95% confidence intervals], 1.99 [1.03-3.83] and 2.14 [1.32-3.47], respectively). Phenotypes reflecting defective quorum sensing were significantly associated with subsequent mucoidy, but no phenotype was significantly associated with subsequent exacerbations during the trial. CONCLUSIONS: Pseudomonas aeruginosa phenotypes commonly considered to reflect chronic adaptation were observed frequently among isolates at early detection. We found that 2 easily assayed colony phenotypes were associated with failure to eradicate after antipseudomonal therapy, both of which have been previously associated with altered biofilm formation and defective quorum sensing.

Staphylococcus aureus small-colony variants are independently associated with worse lung disease in children with cystic fibrosis.

BACKGROUND: Cystic fibrosis (CF) lung disease is associated with diverse bacteria chronically infecting the airways. Slow-growing, antibiotic-resistant mutants of Staphylococcus aureus known as small-colony variants (SCVs) have been isolated from respiratory secretions from European adults and children with CF lung disease using specific but infrequently used culture techniques. Staphylococcus aureus SCVs can be selected either by exposure to specific antibiotics or by growth with another CF pathogen, Pseudomonas aeruginosa. We sought to determine the prevalence, clinical significance, and likely mechanisms of selection of S. aureus SCVs among a US cohort of children with CF. METHODS: We performed a 2-year study of 100 children with CF using culture techniques sensitive for S. aureus SCVs, and evaluated associations with clinical characteristics using multivariable regression models. RESULTS: Staphylococcus aureus SCV infection was detected among 24% of participants and was significantly associated with a greater drop in lung function during the study (P = .007, adjusted for age and lung function at enrollment). This association persisted after adjusting for infection with other known CF pathogens, including P. aeruginosa and methicillin-resistant S. aureus. Evidence indicated that S. aureus SCVs were likely selected in vivo by treatment with the antibiotic trimethoprim-sulfamethoxazole and possibly by coinfection with P. aeruginosa. CONCLUSIONS: Infection with SCV S. aureus was independently associated with worse CF respiratory outcomes in this pediatric cohort. As many clinical microbiology laboratories do not specifically detect S. aureus SCVs, validation and extension of these findings would require widespread changes in the usual laboratory and clinical approaches to these bacteria.

Nutrient availability as a mechanism for selection of antibiotic tolerant Pseudomonas aeruginosa within the CF airway.

Microbes are subjected to selective pressures during chronic infections of host tissues. Pseudomonas aeruginosa isolates with inactivating mutations in the transcriptional regulator LasR are frequently selected within the airways of people with cystic fibrosis (CF), and infection with these isolates has been associated with poorer lung function outcomes. The mechanisms underlying selection for lasR mutation are unknown but have been postulated to involve the abundance of specific nutrients within CF airway secretions. We characterized lasR mutant P. aeruginosa strains and isolates to identify conditions found in CF airways that select for growth of lasR mutants. Relative to wild-type P. aeruginosa, lasR mutants exhibited a dramatic metabolic shift, including decreased oxygen consumption and increased nitrate utilization, that is predicted to confer increased fitness within the nutrient conditions known to occur in CF airways. This metabolic shift exhibited by lasR mutants conferred resistance to two antibiotics used frequently in CF care, tobramycin and ciprofloxacin, even under oxygen-dependent growth conditions, yet selection for these mutants in vitro did not require preceding antibiotic exposure. The selection for loss of LasR function in vivo, and the associated adverse clinical impact, could be due to increased bacterial growth in the oxygen-poor and nitrate-rich CF airway, and from the resulting resistance to therapeutic antibiotics. The metabolic similarities among diverse chronic infection-adapted bacteria suggest a common mode of adaptation and antibiotic resistance during chronic infection that is primarily driven by bacterial metabolic shifts in response to nutrient availability within host tissues.

Pseudomonas aeruginosa lasR mutants are associated with cystic fibrosis lung disease progression.

BACKGROUND: Pseudomonas aeruginosa with mutations in the transcriptional regulator LasR chronically infect the airways of people with cystic fibrosis (CF), yet the prevalence and clinical implications of lasR mutant infection are unknown. METHODS: In an exploratory study, we screened 166 P. aeruginosa isolates from 58 CF patients for LasR inactivation and mucoidy, and compared clinical characteristics among source patients. RESULTS: lasR mutation prevalence was comparable to that of mucoidy, the best-described CF-adapted phenotype, but affected patients were on average approximately 2 years younger. In a regression analysis, lung function decline with age was worse among patients with lasR mutant infection than in those without, similar to the effect of mucoidy. CONCLUSIONS: Culture positivity for lasR mutant P. aeruginosa may serve as a marker of early CF adaptive change of prognostic significance. Furthermore, as LasR inactivation alters susceptibility to antibiotics, infection with lasR mutant P. aeruginosa may impact response to therapy.

Mycoplasma genitalium among young adults in the United States: an emerging sexually transmitted infection.

OBJECTIVES: We sought to determine the prevalence of and risk factors associated with Mycoplasma genitalium infection in a nationally representative sample of young adults in the United States. METHODS: Urine specimens from 1714 women and 1218 men who participated in Wave III of the National Longitudinal Study of Adolescent Health (N=14322) were tested for M genitalium. Poststratification sampling weights were used to generate nationally representative estimates. RESULTS: The prevalence of M genitalium was 1.0% compared with 0.4%, 4.2%, and 2.3% for gonococcal, chlamydial, and trichomonal infections, respectively. No M genitalium-positive individuals reported symptoms of discharge. M genitalium prevalence among those who reported vaginal intercourse was 1.1% compared with 0.05% among those who did not. In multivariate analyses, M genitalium prevalence was 11 times higher among respondents who reported living with a sexual partner, 7 times higher among Blacks, and 4 times higher among those who used condoms during their last vaginal intercourse. Prevalence of M genitalium increased by 10% for each additional sexual partner. CONCLUSIONS: M genitalium was more prevalent than Neisseria gonorrhoeae but less prevalent than Chlamydia trachomatis, and it was strongly associated with sexual activity.

Periodontitis vaccine decreases local prostaglandin E2 levels in a primate model.

Interleukin-1beta, tumor necrosis factor alpha, prostaglandin E2 (PGE2), and Porphyromonas gingivalis-specific immunoglobulin G levels in gingival crevicular fluid were measured in primates immunized with a P. gingivalis vaccine followed by ligature-induced periodontitis. Only PGE2 levels were dramatically suppressed (P < 0.0001) in immunized animals versus controls. A significant correlation (P < 0.027) was also found between PGE2 levels and decreased bone loss scores. This study presents the first evidence of a potential mechanism involved in periodontitis vaccine-induced suppression of bone loss in a nonhuman primate model and offers insight into the role of PGE2 in periodontal destruction.