Ronald L. Gibson

Longitudinal Assessment of Pseudomonas aeruginosa in Young Children with Cystic Fibrosis

Pseudomonas aeruginosa lung infection is an important cause of morbidity and mortality in cystic fibrosis (CF). Longitudinal assessment of the phenotypic changes in P. aeruginosa isolated from young children with CF is lacking. This study investigated genotypic and phenotypic changes in P. aeruginosa from oropharynx (OP) and bronchoalveolar lavage fluid (BALF) in a cohort of 40 CF patients during the first 3 years of life; antibody response was also examined. A high degree of genotypic variability was identified, and each patient had unique genotypes. Early isolates had a phenotype distinct from those of usual CF isolates: generally nonmucoid and antibiotic susceptible. Genotype and phenotype correlated between OP and BALF isolates. As determined by culture, 72.5% of patients demonstrated P. aeruginosa during their first 3 years. On the basis of combined culture and serologic results, 97.5% of patients had evidence of infection by age 3 years, which suggests that P. aeruginosa infection occurs early in CF and may be intermittent or undetectable by culture.

Efficacy of aerosolized tobramycin in patients with cystic fibrosis.

BACKGROUND Direct aerosol delivery of aminoglycosides such as tobramycin to the lower airways of patients with cystic fibrosis may control infection with Pseudomonas aeruginosa and improve pulmonary function, with low systemic toxicity. We conducted a randomized crossover study to evaluate the safety and efficacy of aerosolized tobramycin in patients with cystic fibrosis and P. aeruginosa infections. METHODS Seventy-one patients with stable pulmonary status were recruited from seven U.S. centers for the treatment of cystic fibrosis and randomly assigned to one of two crossover regimens. Group 1 received 600 mg of aerosolized tobramycin for 28 days, followed by half-strength physiologic saline (placebo) for two 28-day period. Group 2 received placebo for 28 days, followed by tobramycin for two 28-day periods. Pulmonary function, the density of P. aeruginosa in sputum, ototoxicity, nephrotoxicity, and the emergence of tobramycin-resistant P. aeruginosa were monitored. RESULTS In the first 28-day period, treatment with tobramycin was associated with an increase in the percentage of the value predicted for forced expiratory volume in one second (9.7 percentage points higher than the value for placebo; P < 0.001), forced vital capacity (6.2 percentage points higher than the value for placebo; P = 0.014), and forced expiratory flow at the midportion of the vital capacity (13.0 percentage points higher than the value for placebo; P < 0.001). A decrease in the density of P. aeruginosa in sputum by a factor of 100 (P < 0.001) was found during all periods of tobramycin administration. Neither ototoxicity nor nephrotoxicity was detected. The frequency of the emergence of tobramycin-resistant bacteria was similar during both tobramycin and placebo administration. CONCLUSIONS The short-term aerosol administration of a high dose of tobramycin in patients with clinically stable cystic fibrosis is an efficacious and safe treatment for endobronchial infection with P. aeruginosa.

Inhaled Aztreonam Lysine for Chronic Airway Pseudomonas aeruginosa in Cystic Fibrosis

RATIONALE The effectiveness and safety of aztreonam lysine for inhalation (AZLI) in patients with cystic fibrosis (CF) on maintenance treatment for Pseudomonas aeruginosa (PA) airway infection was evaluated in this randomized, double-blind, placebo-controlled study. OBJECTIVES To evaluate the safety and efficacy of inhaled aztreonam lysine in controlling PA infection in patients with CF. METHODS After randomization and a 28-day course of tobramycin inhalation solution (TIS), patients (n = 211; > or =6 yr; > or =3 TIS courses within previous year; FEV(1) > or = 25% and < or =75% predicted values) were treated with 75 mg AZLI or placebo, twice or three times daily for 28 days, then monitored for 56 days. The primary efficacy endpoint was time to need for additional inhaled or intravenous antipseudomonal antibiotics. Secondary endpoints included changes in respiratory symptoms (CF Questionnaire-Revised [CFQ-R] Respiratory Scale), pulmonary function (FEV(1)), and sputum PA density. Adverse events and minimum inhibitory concentrations of aztreonam for PA were monitored. MEASUREMENTS AND MAIN RESULTS AZLI treatment increased median time to need for additional antipseudomonal antibiotics for symptoms of pulmonary exacerbation by 21 days, compared with placebo (AZLI, 92 d; placebo, 71 d; P = 0.007). AZLI improved mean CFQ-R respiratory scores (5.01 points, P = 0.02), FEV(1) (6.3%, P = 0.001), and sputum PA density (-0.66 log(10) cfu/g, P = 0.006) compared with placebo; no AZLI dose-response was observed. Adverse events reported for AZLI and placebo were comparable and consistent with CF lung disease. Susceptibility of PA to aztreonam at baseline and end of therapy were similar. CONCLUSIONS AZLI was effective in patients with CF using frequent TIS therapy. AZLI delayed time to need for inhaled or intravenous antipseudomonal antibiotics, improved respiratory symptoms and pulmonary function, and was well tolerated. Clinical trial registered with www.clinicaltrials.gov (NCT 00104520).

Repeat administration of an adenovirus vector encoding cystic fibrosis transmembrane conductance regulator to the nasal epithelium of patients with cystic fibrosis.

Cystic fibrosis (CF) is a common autosomal recessive disease caused by mutations in the CF transmembrane conductance regulator gene. Recombinant adenoviruses have shown promise as vectors for transfer of CF transmembrane conductance regulator cDNA to airway epithelia and correction of the Cl- transport defect. However, because adenovirus-mediated gene transfer is transient, use of adenovirus as a vector for treatment of CF would require repeated administration. Therefore, we evaluated repeat administration of an adenovirus vector to the nasal epithelium of patients with CF with five escalating doses of up to 10(10) infectious units. There were no detectable adverse affects. All subjects were initially seropositive but developed additional humoral immune responses. The vector partially corrected the defect in airway epithelial Cl- transport in some subjects, although there was variability between subjects and there was less correction with subsequent administration, perhaps because the immune response limited gene transfer. Future work must focus on vectors with increased efficiency and with the ability to evade host defenses.

Selection for Staphylococcus aureus small-colony variants due to growth in the presence of Pseudomonas aeruginosa

Opportunistic infections are often polymicrobial. Two of the most important bacterial opportunistic pathogens of humans, Pseudomonas aeruginosa and Staphylococcus aureus, frequently are coisolated from infections of catheters, endotracheal tubes, skin, eyes, and the respiratory tract, including the airways of people with cystic fibrosis (CF). Here, we show that suppression of S. aureus respiration by a P. aeruginosa exoproduct, 4-hydroxy-2-heptylquinoline-N-oxide (HQNO), protects S. aureus during coculture from killing by commonly used aminoglycoside antibiotics such as tobramycin. Furthermore, prolonged growth of S. aureus with either P. aeruginosa or with physiological concentrations of pure HQNO selects for typical S. aureus small-colony variants (SCVs), well known for stable aminoglycoside resistance and persistence in chronic infections, including those found in CF. We detected HQNO in the sputum of CF patients infected with P. aeruginosa, but not in uninfected patients, suggesting that this HQNO-mediated interspecies interaction occurs in CF airways. Thus, in all coinfections with P. aeruginosa, S. aureus may be underappreciated as a pathogen because of the formation of antibiotic-resistant and difficult to detect small-colony variants. Interspecies microbial interactions, analogous to those mediated by HQNO, commonly may alter not only the course of disease and the response to therapy, but also the population structure of bacterial communities that promote the health of host animals, plants, and ecosystems.

A Phase I Study of Aerosolized Administration of tgAAVCF to Cystic Fibrosis Subjects with Mild Lung Disease

Cystic fibrosis (CF) is one of the most common autosomal recessive disorders in North America, leading to significant morbidity and early mortality. The defect in the cystic fibrosis transmembrane conductance regulator protein (CFTR) function can be corrected in vitro by gene replacement with a wild-type gene. A Phase I, single administration, dose escalation trial was designed and executed to assess safety and delivery of tgAAVCF, an adeno-associated virus (AAV) vector encoding the human CFTR cDNA, by nebulization to the lungs of CF subjects. Four cohorts of three subjects each were administered increasing doses of the study agent, beginning with 10(10) DNase-resistant particles (DRP) and escalating in log increments up to 10(13) DRP. Sequential bronchoscopies were performed to gather analytical samples throughout the study. All 12 subjects completed the study. There were a total of 242 adverse events (AEs), six of which were defined as serious and three of which were defined as possibly being related to the study drug. A clear dose-response relationship was observed in vector gene transfer. A maximum of 0.6 and 0.1 vector copies per brushed cell were observed 14 days and 30 days, respectively, following nebulization of 10(13) DRP tgAAVCF, and this declined to nearly undetectable levels by day 90. Vector gene transfer was evenly distributed throughout the fourth airway generation following single-dose administration. RNA-specific PCR did not detect vector-derived mRNA. This Phase I trial shows that aerosolized tgAAVCF is safe and widely delivered to the proximal airways of CF subjects by nebulization.

An 18-Month Study of the Safety and Efficacy of Repeated Courses of Inhaled Aztreonam Lysine in Cystic Fibrosis

Chronic airway infection with Pseudomonas aeruginosa (PA) causes morbidity and mortality in patients with cystic fibrosis (CF). Additional anti‐PA therapies are needed to improve health status and health‐related quality of life. AIR‐CF3 was an international 18‐month, open‐label study to evaluate the safety and efficacy of repeated courses of aztreonam for inhalation solution (AZLI, now marketed as Cayston®) in patients aged ≥6 years with CF and PA infection who previously participated in one of two Phase 3 studies: AIR‐CF1 or AIR‐CF2. Patients received up to nine courses (28 days on/28 days off) of 75 mg AZLI two (BID) or three times daily (TID) based on randomization in the previous trials. 274 patients, mean age 28.5 years (range: 8–74 years), participated. Mean treatment adherence was high (92.0% BID group, 88.0% TID group). Hospitalization rates were low and adverse events were consistent with CF. With each course of AZLI, FEV1 and scores on the Cystic Fibrosis Questionnaire‐Revised Respiratory Symptom scale improved and bacterial density in sputum was reduced. Benefits waned in the 28 days off therapy, but weight gain was sustained over the 18 months. There were no sustained decreases in PA susceptibility. A dose response was observed; AZLI TID‐treated patients demonstrated greater improvements in lung function and respiratory symptoms over 18 months. Repeated intermittent 28‐day courses of AZLI treatment were well tolerated. Clinical benefits in pulmonary function, health‐related quality of life, and weight were observed with each course of therapy. AZLI is a safe and effective new therapy in patients with CF and PA airway infection. Pediatr Pulmonol. 2010;45:1121–1134.

Exome sequencing of extreme phenotypes identifies DCTN4 as a modifier of chronic Pseudomonas aeruginosa infection in cystic fibrosis

Exome sequencing has become a powerful and effective strategy for the discovery of genes underlying Mendelian disorders. However, use of exome sequencing to identify variants associated with complex traits has been more challenging, partly because the sample sizes needed for adequate power may be very large. One strategy to increase efficiency is to sequence individuals who are at both ends of a phenotype distribution (those with extreme phenotypes). Because the frequency of alleles that contribute to the trait are enriched in one or both phenotype extremes, a modest sample size can potentially be used to identify novel candidate genes and/or alleles. As part of the National Heart, Lung, and Blood Institute (NHLBI) Exome Sequencing Project (ESP), we used an extreme phenotype study design to discover that variants in DCTN4, encoding a dynactin protein, are associated with time to first P. aeruginosa airway infection, chronic P. aeruginosa infection and mucoid P. aeruginosa in individuals with cystic fibrosis.

Comparative Efficacy and Safety of 4 Randomized Regimens to Treat Early Pseudomonas aeruginosa Infection in Children With Cystic Fibrosis

OBJECTIVE To investigate the efficacy and safety of 4 antipseudomonal treatments in children with cystic fibrosis with recently acquired Pseudomonas aeruginosa infection. DESIGN Randomized controlled trial. SETTING Multicenter trial in the United States. PARTICIPANTS Three hundred four children with cystic fibrosis aged 1 to 12 years within 6 months of P aeruginosa detection. INTERVENTIONS Participants were randomized to 1 of 4 antibiotic regimens for 18 months (six 12-week quarters) between December 2004 and June 2009. Participants randomized to cycled therapy received tobramycin inhalation solution (300 mg twice a day) for 28 days, with oral ciprofloxacin (15-20 mg/kg twice a day) or oral placebo for 14 days every quarter, while participants randomized to culture-based therapy received the same treatments only during quarters with positive P aeruginosa cultures. MAIN OUTCOME MEASURES The primary end points were time to pulmonary exacerbation requiring intravenous antibiotics and proportion of P aeruginosa -positive cultures. RESULTS The intention-to-treat analysis included 304 participants. There was no interaction between treatments. There were no statistically significant differences in exacerbation rates between cycled and culture-based groups (hazard ratio, 0.95; 95% confidence interval [CI], 0.54-1.66) or ciprofloxacin and placebo (hazard ratio, 1.45; 95% CI, 0.82-2.54). The odds ratios of P aeruginosa- positive culture comparing the cycled vs culture-based group were 0.78 (95% CI, 0.49-1.23) and 1.10 (95% CI, 0.71-1.71) comparing ciprofloxacin vs placebo. Adverse events were similar across groups. CONCLUSIONS No difference in the rate of exacerbation or prevalence of P aeruginosa positivity was detected between cycled and culture-based therapies. Adding ciprofloxacin produced no benefits. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT00097773.

Percutaneous left ventricular puncture in the assessment of aortic stenosis.

Experience in the selection of patients for aortic valvotomy has shown that two problems commonly arise: first the determination of the severity of the stenosis, and secondly whether the degree of regurgitation is sufficient to preclude successful valvotomy. The clinical aspects of these problems have been discussed recently by Baker and Campbell (1956). The physiological aspects will be considered in this paper. The best method of determining the degree of obstruction to flow through a stenotic valve is by the simultaneous measurement of the pressure gradient across the valve and the blood flow through the valve orifice. This principle has been successfully applied to the study of pulmonary and mitral stenosis. The study of aortic stenosis has been hindered by the lack of a safe and simple method of obtaining the left ventricular pressure. Apart from the pioneer work of Buchbinder and Katz (1949), the first approach to this problem was made by Bjork, Blakemore, and Malmstrom (1954), who introduced a catheter into the left ventricle through a needle directed percutaneously into the left atrium. The method of direct percutaneous left ventricular puncture has been described recently by Brock, Milstein, and Ross (1956), who discuss the reasons for adopting this technique. It is the purpose of this paper to present the results of this investigation in the first 28 patients in whom it has been performed and to discuss their significance. The procedure of left ventricular puncture was initiated by Sir Russell Brock, and carried out by Mr. D. N. Ross at Guys Hospital and by Mr. B. B. Milstein at Brompton Hospital. It was considered that the degree of valve obstruction in pure aortic stenosis could be assessed by the simultaneous measurement of the cardiac output and of the systolic gradient across the aortic valve. However, in aortic stenosis with regurgitation it is impossible to measure the total amount of blood expelled through the aortic valve during systole (total left ventricular output), because measurement of the cardiac output by the Fick principle determines only the effective left ventricular output. Since the systolic gradient across the aortic valve is dependent upon the total left ventricular stroke output (effective output plus diastolic regurgitant volume), assessment of the degree of valve obstruction in aortic stenosis with regurgitation by this method becomes unreliable when the degree of regurgitation is more than trivial. MATERIAL There were 20 men and eight women in this series and their ages ranged from 15 to 67 years. In all the patients a diagnosis of aortic stenosis had been made and aortic valvotomy was under consideration. In 11, no diastolic murmur had been heard at any time and they were considered to have pure aortic stenosis. In the remaining 17, an aortic diastolic murmur was present with or without other clinical evidence of aortic regurgitation; they were regarded as having aortic stenosis with a variable, often unknown, degree of regurgitation. Two patients (Cases 6 and 20*) in the latter group had concomitant mitral stenosis and one patient (Case 12) was found to have subvalvar aortic stenosis at operation. Eighteen patients have been submitted to aortic valvotomy and this group has been subjected to detailed analysis. Of the remaining 10 cases, valvotomy has been advised in one but has not yet been carried out and was considered to be contraindicated in nine.