Inapparent transmission of Pseudomonas (Burkholderia) cepacia among patients with cystic fibrosis.

Pseudomonas cepacia is a significant pathogen in children and young adults with cystic fibrosis, and prevention of its acquisition has become an important goal in patient management. Although it is now clear that this bacterium can be transmitted from person to person, the frequency of this mode of acquisition and the measures required to prevent it are controversial. In this report we describe the use of a novel genotyping method to extend our previous investigation of person to person transmission of P. cepacia among patients with cystic fibrosis attending an educational program. Three (20%) of 15 individuals acquired P. cepacia after contact with a chronically colonized patient. Analysis revealed that the isolates recovered from the three newly colonized patients were the same as that from the index patient. We also demonstrated that pulmonary colonization with P. cepacia may not be detected by currently recommended culture methods for as long as 2 years after acquisition. These data indicate a need to develop more sensitive means of detecting P. cepacia colonization in order better to understand host-pathogen interaction and to optimize preventive strategies.

Anti-Pseudomonas aeruginosa IgG subclass titers in patients with cystic fibrosis: correlations with pulmonary function, neutrophil chemotaxis, and phagocytosis.

To explore possible mechanisms for the association between elevated immunoglobulin levels and lower pulmonary function in cystic fibrosis patients, we measured serum IgG subclass levels and anti-P. aeruginosa IgG subclass titers and correlated levels with neutrophil phagocytosis and chemotaxis. Serum was obtained from 13 cystic fibrosis patients colonized with the same serotype of P. aeruginosa, 12 noncolonized patients, and 12 normal volunteers. All anti-P. aeruginosa IgG subclass titers were elevated in serum from colonized patients. IgG3 level and anti-P. aeruginosa IgG3 titer were inversely correlated with pulmonary function. Phagocytosis of P. aeruginosa by neutrophils correlated with serum IgG3 level and was increased by opsonization with serum from colonized patients. Chemotactic index was increased in serum from colonized patients and inversely correlated with pulmonary function chest roentgenogram score. Chemotactic index directly correlated with anti-P. aeruginosa IgG3 titer and serum IgG3. These data demonstrate that cystic fibrosis patients with increased IgG3 levels are in poorer clinical condition and that their serum enhances neutrophil function. Such patients may have increased pulmonary inflammation with subsequent lung damage.

Association of Epstein-Barr virus infection and pulmonary exacerbations in patients with cystic fibrosis.

We observed severe pulmonary exacerbations during primary Epstein-Barr virus (EBV) infection in adolescent patients with cystic fibrosis. Since EBV is not a known respiratory tract pathogen in cystic fibrosis, we studied retrospectively all EBV-susceptible patients ages 6 to 18 years with chronic Pseudomonas respiratory tract colonization hospitalized for a pulmonary exacerbation during an 18-month period. Patients with serologic evidence of primary EBV infection (n = 5) were compared to control patients without EBV (n = 7). Before admission the groups had similar pulmonary function tests, clinical scores and frequency of hospitalization. On admission patients with EBV had significant weight loss, lower pulmonary function tests and lower clinical scores compared with controls. All remained significantly different 6 months after admission. Frequency of exacerbations requiring hospitalization increased after EBV infection but remained unchanged in controls. Primary EBV infection can be associated with severe pulmonary exacerbations and subsequent deterioration in clinical course in cystic fibrosis patients.

Comparison of 6 and 8 hourly tobramycin dosing intervals in treatment of pulmonary exacerbations in cystic fibrosis patients.

The efficacy and toxicity of a shortened tobramycin dosing interval in the treatment of exacerbations of Pseudomonas aeruginosa pulmonary infection in cystic fibrosis patients were evaluated prospectively. Patients ages 13 to 30 years received 34 treatment courses and were randomized by pairs to receive tobramycin administered either every 6 or 8 hours. Peak serum concentrations were adjusted to 8 to 10 micrograms/ml; thus a larger total daily dosage was administered to patients receiving tobramycin every 6 hours. The shorter dosing interval was associated with better pulmonary function at follow-up and significantly longer time before next hospital admission for a pulmonary exacerbation. During the study hospitalization there were no differences in pulmonary function tests, clinical score, sputum carriage of P. aeruginosa, toxicity or necessary length of hospitalization. A 6-hour tobramycin dosing interval was more efficacious than an 8-hour dosing interval in the treatment of cystic fibrosis patients.

Respiratory tract colonization with Pseudomonas aeruginosa in cystic fibrosis: correlations between anti-Pseudomonas aeruginosa antibody levels and pulmonary function.

Chronic Pseudomonas aeruginosa respiratory tract colonization in patients with cystic fibrosis is associated with development of antibodies to the organism. In contrast to the protection usually afforded by humoral immunity to a bacterial pathogen, the immune response to P. aeruginosa may help perpetuate infection and contribute to pulmonary damage in cystic fibrosis. To determine if specific anti-P. aeruginosa antibody levels correlated with pulmonary dysfunction, we measured antibodies to seven P. aeruginosa serotypes, and correlated the geometric mean titer with pulmonary function tests. Patients were divided into groups without P. aeruginosa colonization (n = 20), with recent colonization (n = 20), and with chronic colonization (n = 60). Noncolonized patients had normal pulmonary function or mild obstructive lung disease, and low anti-P. aeruginosa titers. Pulmonary function tests in recently colonized patients were not different from those of noncolonized patients, but antibody titers were higher. Following colonization FEV1 declined and titers increased rapidly. Patients with chronic colonization had worse pulmonary function and higher titers, but while the former were stable the latter gradually increased. An inverse correlation was found between anti-P. aeruginosa titer and FVC, FEV1, and FEF25-75 (P less than 0.001) in these patients; age was not a factor. The strong correlation between severity of lung disease and anti-P. aeruginosa titer demonstrates that an exaggerated immune response to P. aeruginosa is associated with pulmonary damage in patients with cystic fibrosis.

Intravenous immune globulin treatment of pulmonary exacerbations in cystic fibrosis.

The effect of intravenously administered immune globulin (IVIG) on patients with cystic fibrosis with an acute exacerbation of pulmonary infection was evaluated in a double-blind study. Patients at least 12 years of age, with chronic respiratory tract colonization with Pseudomonas aeruginosa and hospitalized with a reduction in pulmonary function, were randomly assigned to receive 20% dextrose (control subjects: n = 8) or 100 mg/kg IVIG (Gamimune) (experimental subjects: n = 8) on days 1, 2, and 3; all patients received intravenous antibiotics and chest physiotherapy. There were no differences between groups on admission; patients had moderate to severe disease as measured by Shwachman-Kulczycki scores and pulmonary function tests. Both groups improved clinically. The IVIG treatment was associated with significant increases in forced vital capacity and forced expiratory volume in 1 second (p less than 0.01) and with greater percent improvement in forced expiratory volume and forced expiratory flow (25% to 75%) (p less than 0.05). There was no effect on length of hospitalization (18.3 +/- 11.9 days control vs 17.6 +/- 6.5 experimental). The C3 level was decreased at discharge in IVIG-treated patients; circulating immune complex levels were unchanged. One patient in each group experienced side effects. There were no differences on follow-up at 6 weeks. We conclude that IVIG infusion early in treatment for pulmonary exacerbations in cystic fibrosis patients with moderate to severe disease may be associated with greater improvement in pulmonary function than standard treatment alone.

Pulmonary cellular response to chronic irritation and chronic Pseudomonas aeruginosa pneumonia in cats.

A model of chronic pulmonary infection was used for studying cellular events in a sequential manner. In this model, agarose beads containing Pseudomonas aeruginosa were instilled endotracheally into cats. Nine cats were inoculated with agarose beads containing P. aeruginosa, and four others were inoculated with sterile beads. With a fiberoptic bronchoscope, bronchial washings were obtained biweekly for up to 30 weeks. The quantitative pulmonary inflammatory cell response and alveolar macrophage morphology of the animals exposed to P. aeruginosa were compared with those for the animals exposed to a chronic irritant (agarose beads). Bronchial washings of all animals before inoculation showed that 70 to 90% of the cells were macrophages. After inoculation with P. aeruginosa, a persistent inflammatory response was observed (60 to 70% granulocytes). In the sterile-bead-inoculated group, the response was less prominent (30 to 40% granulocytes). As early as 2 weeks after inoculation, alveolar macrophages from infected animals were larger and had cytoplasmic features that differed from those of controls. Electron microscope examination showed prominent surface alterations in alveolar macrophages from the infected cats. These alterations persisted from 2 to 12 weeks after infection. In animals inoculated with sterile beads, alveolar macrophages exhibited less extensive surface changes that had resolved by week 8. Histologically, chronic bronchiolitis and pneumonia were more severe in the infected animals than in controls. This model of chronic inflammation and macrophage stimulation, which is similar to the chronic pneumonia of cystic fibrosis, may be a useful approach to answer questions on the role of macrophage activation in chronic lung disease.

Function of human alveolar macrophages from normal volunteers and cigarette smokers: effect of cystic fibrosis serum.

Previous studies demonstrated that serum from cystic fibrosis (CF) patients specifically inhibited Pseudomonas phagocytosis by both normal and CF alveolar macrophages. In the present study, inhibition of Pseudomonas aeruginosa phagocytosis by CF serum was significantly less on macrophages from heavy smokers than on cells from normal volunteers (P less than 0.01). Normal volunteer cells cultured for 10 days were also less affected by CF serum as compared to cells cultured for 24 hours from the same individual (P less than 0.01). Altered morphology (increased size and spreading on glass surfaces) and increased intracellular glycosidases of these cells were suggestive of a difference in the state of activation compared to normal cells. Macrophages from heavy smokers and 10-day cultures from normal volunteers were inhibited by heated CF serum, suggesting that complement-mediated opsonization was responsible for attachment or ingestion of P. aeruginosa in CF serum by these macrophages.

Induction of phagocytic inhibitory activity in cats with chronic Pseudomonas aeruginosa pulmonary infection.

Chronic pulmonary infection has been established in cats by repeated intrapulmonary inoculation of viable Pseudomonas aeruginosa enmeshed in agarose beads. In the serum of all chronically infected animals, a substance(s) developed which inhibited phagocytosis of P. aeruginosa by normal cat alveolar macrophages. Phagocytosis was measured by incubating macrophage monolayers (5 X 10(5) alveolar macrophages) for 20 min in the presence of 3H-labeled bacteria and 5% serum from control or infected animals. Inhibitory activity developed 4 to 16 weeks after initial infection, and inhibition of phagocytosis of P. aeruginosa in the presence of infected cat serum ranged from 30 to 79%. After inhibitory activity developed, it persisted throughout the remainder of the experiment in each animal. The activity was specific for P. aeruginosa of the infecting serotype and did not affect phagocytosis of gram-positive organisms. Inhibitory activity was unchanged by heating serum at 56 degrees C for 30 min. We have previously described a P. aeruginosa-specific, heat-stable, phagocytosis-inhibitory activity in the serum of patients with cystic fibrosis. Since inhibitory activity also develops in cats with chronic P. aeruginosa pulmonary infection, such activity may not be a primary intrinsic abnormality in patients with cystic fibrosis. The animal model described here offers a system for following the development of and for characterization of the P. aeruginosa-specific phagocytosis-inhibitory activity.