Levels of free granulocyte elastase in bronchial secretions from patients with cystic fibrosis: effect of antimicrobial treatment against Pseudomonas aeruginosa

Large amounts of free granulocyte elastase (GE), an enzyme capable of mediating airway damage, have been found in bronchial secretions of patients with cystic fibrosis who are infected with Pseudomonas aeruginosa. This finding indicates an imbalance between GE and its antiproteases, alpha 1-proteinase inhibitor (alpha 1-PI) and bronchial mucosal inhibitor (BMI), in the airways of these individuals. The effect of intravenous antimicrobial treatment against P. aeruginosa on activity and concentration of GE, BMI, and alpha 1-PI was evaluated in 30 treatment courses of 20 patients with cystic fibrosis. Although sputum volume and level of immunoreactive GE decreased and concentrations of alpha 1-PI and BMI increased significantly (P less than .05), a high level of free GE persisted. No active alpha 1-PI and BMI were detectable after treatment. High levels of GE correlated with a poor pulmonary condition (rs = .98, P less than .001). In vitro, elastolytic activity of bronchial secretions from patients with cystic fibrosis was significantly inhibited by eglin C and an oxidation-resistant variant of alpha 1-PI, both compounds currently produced by recombinant DNA technology.     

Proteases of Pseudomonas aeruginosa in patients with cystic fibrosis

Radioimmunoassays were used to determine titers of antibody to alkaline protease (AP) and elastase (Ela) produced by Pseudomonas aeruginosa in sera and bronchial secretions, in vitro production of AP and Ela by P. aeruginosa isolates, and occurrence of these enzymes in bronchial secretions from patients with cystic fibrosis. Titers of serum antibodies to AP ranging from 1:10 to 1:545 and to Ela ranging from 1:10 to 1:725 were found in 83%-88% of patients with cystic fibrosis and chronic lung infections due to P. aeruginosa. Antibody titers in liquified bronchial secretions were approximately 10% of the serum titers. Thirty-one (93%) of 34 isolates produced both proteases in vitro in comparable amounts (concentration of protease in culture supernatant: AP, 0.01-480 micrograms/ml; Ela, 0.02-490 micrograms/ml). AP and Ela were detected in vivo when antibodies to the enzymes were absent. The results suggest that specific immune responses in patients with cystic fibrosis neutralize proteases of P. aeruginosa.     

Granulocyte neutral proteases and Pseudomonas elastase as possible causes of airway damage in patients with cystic fibrosis

We studied the possible role of granulocyte neutral proteases as mediators of airway destruction in patients with cystic fibrosis (CF) who were infected with Pseudomonas aeruginosa. We measured the enzymatic activities of bronchial secretions on purified radioactively labeled complement component three (C3), elastin, and a granulocyte elastase-specific substrate. Bronchial secretions from 18 patients with CF who were infected with P aeruginosa had a significantly higher mean value for C3 cleaving, elastolytic, and granulocyte elastase-like activity than did two control groups. High enzymatic activities were observed in patients with CF who have advanced bronchial disease (that had been determined by a clinical scoring system). Kinetics of proteolysis of radioactively labeled C3 and inhibition profiles of the activities of the three enzymatic activities studied suggest that they are mainly derived from granulocytes. In addition, 20 of 31 strains of P aeruginosa isolated from patients with CF inactivated purified alpha 1-antiprotease in vitro. We postulate that granulocyte neutral proteases and P aeruginosa may act synergistically in the airways of patients with CF and may contribute to the destruction of elastin and inactivation of C3.     

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.     

Evidence that Pseudomonas aeruginosa elastase does not inactivate the bronchial inhibitor in the presence of leukocyte elastase. Studies with cystic fibrosis sputum and with pure proteins

Pseudomonas aeruginosa elastase has recently been shown to inactivate bronchial inhibitor, the major leukoproteinase inhibitor of the bronchial tree. To test if this in vitro finding is relevant to pathology, we have measured the leukocyte elastase inhibitory capacity and the immunoreactive levels of bronchial inhibitor in the acidified and neutralized sputum specimens from 15 patients with cystic fibrosis, 11 of whom were infected by P. aeruginosa and 10 of whom exhibited free bacterial elastase activity. The percentage of functionally active bronchial inhibitor in these acid-treated sputum specimens (i.e., concentration of active inhibitor/concentration of immunoreactive inhibitor X 100) was found to be 125 +/- 17%. It was positively correlated with the free leukocyte elastase concentration (r = 0.77, p less than 0.001) but not with the free bacterial elastase concentration (r = 0.46, p greater than 0.05). Therefore, in an in vivo situation, P. aeruginosa elastase does not necessarily inactivate the bronchial inhibitor. Experiments using pure proteins show that the inactivation process does not take place when leukocyte and P. aeruginosa elastase are added simultaneously to the inhibitor. This suggests that the bronchial inhibitor reacts preferentially with leukocyte elastase and that in its complexed form it is shielded from the inactivating action of P. aeruginosa elastase. In addition, the inhibitor recovered from the acid-induced dissociation of the leukocyte elastase-inhibitor complexes, exhibits a substantially higher specific activity than does the native molecule. This explains why the average functional activity of the bronchial inhibitor is significantly higher than 100% in sputum samples from patients with cystic fibrosis.(ABSTRACT TRUNCATED AT 250 WORDS)     

Antibodies to proteases and exotoxin A of Pseudomonas aeruginosa in patients with cystic fibrosis: Demonstration by radioimmunoassay.

Sera from 33 patients with cystic fibrosis and two pediatric patients being treated for chronic pulmonary infections not related to cystic fibrosis and six sera or serum pools from uninfected individuals were tested with a microtiter radioimmunoassay for reactivity against exotoxin A and two proteases from Pseudomonas aeruginosa. Exotoxin A was purified from a low-protease strain of P. aeruginosa and shown to have adenosine diphosphate-ribose transferase activity and mouse lethality. Proteases were purified from an isolate of P. aeruginosa from a patient with cystic fibrosis and had proteolytic activity against elastin and collagen in an assay employing dimethylated protein substrates. The antibody responses of the patients detected using 125I-labeled antibody to human immunoglobulin were correlated with clinical evaluations expressed as a composite score based on pulmonary findings, case histories, growth and nutrition, and chest X rays. Values in the radioimmunoassay for patients' sera were compared with those of a control serum pool and expressed as the ratio of counts per minute (cpm) in patient serum to the cpm in the control pool. Inverse correlations were found between these ratios for each of the pseudomonas exoproducts and clinical scores; highest ratios occurred in patients showing the lowest clinical scores. These results confirm that proteases and exotoxin A of P. aeruginosa are produced in cystic fibrosis pulmonary infections due to P. aeruginosa and suggest that they may serve as significant virulence factors in these chronic infectious states.     

Pseudomonas aeruginosa infection in cystic fibrosis. Diagnostic and prognostic significance of Pseudomonas aeruginosa precipitins determined by means of crossed immunoelectrophoresis.

A total of 133 patients with cystic fibrosis have been followed for up to 5 years with monthly examinations including bacteriological examinations of sputum. Sera from the patients were examined by means of crossed immunoelectrophoresis for the occurence and number of precipitating antibody specificites against Pseudomonas aeruginosa. Poor prognosis in cystic fibrosis was associated with chronic colonization (9 months - more than 5 years) of the respiratory tract with mucoid Pseudomonas aeruginosa, and with an onset of the chronic colonization before puberty. Among the patients with chronic Pseudomonas aeruginosa colonization, poor prognosis was associated with high numbers of precipitins against antigens from these bacteria (up to 61). The number of Pseudomonas aeruginosa precipitins increased on an average with five per year in chronically colonized patients. Rapidly increasing number of precipitins was associated with poor prognosis. Patients with any degree of impairment of the ventilatory function and any changes on the chest radiographs could contract chronic Pseudomonas aeruginosa colonization. Poor ventilatory function and severe changes on the chest radiographs was associated with high numbers of Pseudomonas aeruginosa precipitins and with poor prognosis. Although many O groups of Pseudomonas aeruginosa were found in the chronically colonized group of patients, 53% of the patients harboured strains belonging to O group 3 or 3/9, and the highest numbers of precipitins were found in serum from these patients.     

Antibiotic therapy against Pseudomonas aeruginosa in cystic fibrosis: a European consensus.

Cystic fibrosis (CF) is the most common lethal hereditary disorder with autosomal recessive heredity in caucasians. The majority of CF patients suffer from chronic respiratory infection with the opportunistic bacterial pathogen Pseudomonas aeruginosa. No consensus among clinicians has been reached so far concerning antibiotic treatment against P. aeruginosa in CF patients. Consensus answers to 24 important questions in this context, based on current evidence, are presented, given by a panel of 34 European experts. Questions addressed and answered are: The diagnosis of P. aeruginosa lung colonization in CF; The impact of P. aeruginosa on the clinical state of CF patients; The assessment of P. aeruginosa susceptibility against antibiotics and the importance of these results for the clinician; The use of monotherapy versus combination therapy; The development of microbial resistance; The achievement of optimal airway concentrations; The effects of subinhibitory concentrations of antibiotics on P. aeruginosa; Statements on the pharmacokinetics of antibiotics in CF patients; Recommendations for doses and dosing intervals and length of treatment regimens; and Toxic side effects due to repeated antibiotic therapy was addressed. The expert panel answered further questions on the use of fluoroquinolones in children with CF, on the administration of nebulized antibiotics and whether prevention of P. aeruginosa lung colonization is possible in CF using antibiotic therapy. Problems of antibiotic therapy at home and in the hospital were addressed, a consensus statement on regular maintenance treatment, or treatment on demand, was given and different routes of administration of antibiotics were recommended for different clinical situations. Finally, the factors which determine the choice of the antibiotic, the dosage, and the duration of the treatment in cystic fibrosis patients were addressed and the design of future antibiotic studies in the context of Pseudomonas aeruginosa lung infection in cystic fibrosis patients were recommended.     

Relation between tumor necrosis factor-alpha and granulocyte elastase-alpha 1-proteinase inhibitor complexes in the plasma of patients with cystic fibrosis

Patients with cystic fibrosis suffer from a chronic, progressively destructive bronchitis characterized by colonization of the airways by Pseudomonas aeruginosa. Cell wall lipopolysaccharides from P. aeruginosa may stimulate secretion of cytokines such as tumor necrosis factor alpha (TNF alpha) by monocytes/macrophages. We found elevated levels of TNF alpha (150 +/- 60 pg/ml), interleukin-1 alpha (144 +/- 205 pg/ml), and interleukin-1 beta (62 +/- 100 pg/ml) in plasma from 25 patients with cystic fibrosis. In patients with less advanced disease, elevated plasma levels of TNF alpha correlated with high levels of complexes between neutrophil elastase and alpha 1-proteinase inhibitor, suggesting that TNF alpha may be a mediator of neutrophil degranulation. TNF alpha, by its chemotactic effect on neutrophils, may also contribute to the massive influx of neutrophils into and around the bronchial tree. Our findings raise the questions whether in patients with cystic fibrosis TNF alpha acts as cachectin and whether it mediates the anorexia that often results in weight loss.     

Microbiologic contamination study of nebulizers after aerosol therapy in patients with cystic fibrosis

BACKGROUND: To evaluate the contamination of delivery systems after an aerosol therapy session in patients with cystic fibrosis who have chronic Pseudomonas aeruginosa infection. METHODS: Fifty-three patients with cystic fibrosis were enrolled in the study from March 1996 to June 1997. All patients were age 7 years or older and had P aeruginosa infection. They also had been treated with recombinant deoxyribonuclease and were capable of producing sputum for culture. RESULTS: Nine devices were excluded for the study. A total of 44 nebulizers were included: 37 from patients with P aeruginosa colonization with a count of 10(6) colony-forming units/mL or more and 7 with a count of between 10(5) colony-forming units/mL and 10(6) colony-forming units/mL. CONCLUSION: This study demonstrates that in the absence of cleaning, nebulizers of patients with cystic fibrosis who are infected with P aeruginosa are likely to be contaminated by a pathogenic flora.     

Longitudinal serum IgG response to Pseudomonas cepacia surface antigens in cystic fibrosis.

In cystic fibrosis (CF), serum antibody against surface antigens of Pseudomonas aeruginosa is detected only after colonization. Since pulmonary acquisition of P. cepacia usually follows colonization with P. aeruginosa and since P. aeruginosa-colonized patients with CF have demonstrable antibody against outer membrane proteins of P. cepacia, it appears that acquisition of the latter organism occurs in the presence of specific serum antibody. To test this hypothesis, serum obtained from six P. aeruginosa-colonized patients 4 and 2 years prior to and 3 months and 2 years after P. cepacia colonization were assayed for total and specific IgG to P. cepacia outer membrane components. Four patients demonstrated 6-fold or greater increases in specific IgG titers to whole outer membranes following colonization. By immunoblot, all patients had demonstrable serum IgG against the 27- and 36-kDa outer membrane proteins of P. cepacia 4 and 2 years prior to colonization. Immunoblots after P. cepacia acquisition demonstrated an intensification of the 28- and 36-kDa bands and the appearance of antibody to a very low molecular weight compound which was not hydrolyzed by proteinase K and was present in purified LPS. These observations suggest that low serum titers of antibody against two P. cepacia outer membrane proteins are present in patients with CF prior to P. cepacia colonization, and that these antibodies fail to protect for intrinsic or extrinsic reasons.     

Phospholipid composition and surface-active properties of tracheobronchial secretions from patients with cystic fibrosis and chronic obstructive pulmonary diseases.

Among the various components of tracheobronchial secretions, lipids and particularly phospholipids have been shown to influence rheological properties of airway secretions in patients with cystic fibrosis. We studied the phospholipid composition of tracheobronchial secretions, collected from patients suffering from cystic fibrosis (CF) and other chronic obstructive pulmonary diseases (COPD), and we analyzed the possible relationship between the phospholipid profile and the wettability of tracheobronchial secretions evaluated by the measurement of contact angle. Although total phospholipid content and contact angle of tracheobronchial secretions were significantly increased (P less than 0.01) in CF compared to COPD, no significant relationship existed between these two parameters. The concentrations of the different phospholipid subclasses were not homogeneously modified according to the origin of the secretions. Compared to COPD secretions, the CF secretions were characterized by a significant (P less than 0.001) increase in rigidifying fractions such as sphingomyelin and phosphatidylserine/phosphatidylinositol and a significant (P less than 0.001) decrease in surface-active fractions, such as phosphatidylcholine and phosphatidylglycerol (PG) (P less than 0.001). In the two groups, the surface-active phospholipid fraction, PG, was negatively correlated to the contact angle of tracheobronchial secretions. These results suggest that a decrease in PG content in CF secretions may be one factor responsible for an increase in their adhesivity to the respiratory mucosa, and, consequently, for mucus stasis and severity of bronchial obstruction in cystic fibrosis.     

Pseudomonas aeruginosa cross-infection among patients with cystic fibrosis during a winter camp

Twenty-seven patients with cystic fibrosis from our Danish Cystic Fibrosis Center went to a winter camp for 1 week in November of 1990. This study is based on 22 of these patients. Prior to attending camp, 17 out of 22 patients harbored Pseudomonas aeruginosa in their sputum, but 5 patients did not. After returning from camp, all 22 patients harbored P. aeruginosa in the sputum, including the 5 patients whose sputum was free of P. aeruginosa before they went. Epidemiological typing used pulsed-field gel electrophoresis of the P. aeruginosa isolates was performed. The typing results showed that the 5 cystic fibrosis patients who were free of P. aeruginosa in their sputum prior to the winter camp had acquired P. aeruginosa isolates identical to the P. aeruginosa strains isolated from the other 17 cystic fibrosis patients. This constitutes a cross-colonization rate of 100%, the highest rate ever detected among patients with cystic fibrosis. We conclude that separate holiday camps based on the infection status of the patients with cystic fibrosis are necessary to avoid cross-infection of patients not infected with P. aeruginosa.     

Cystic fibrosis epithelial cells have a receptor for pathogenic bacteria on their apical surface.

Chronic colonization and infection of the lung with Pseudomonas aeruginosa is the major cause of morbidity and mortality in cystic fibrosis (CF) patients. We found that polarized CF bronchial and pancreatic epithelia bound P. aeruginosa in a reversible and dose-dependent manner. There was significantly greater binding to CF bronchial and pancreatic cells than to their matched pairs rescued with the wild-type CF transmembrane conductance regulator. Bound P. aeruginosa were easily displaced by unlabeled P. aeruginosa but not by Escherichia coli, an organism that does not cause significant pulmonary disease in CF. In contrast, Staphylococcus aureus, a frequent pathogen in CF, could effectively displace bound P. aeruginosa from its receptor. We found undersialylation of apical proteins and a higher concentration of asialoganglioside 1 (aGM1) in apical membranes of CF compared with rescued epithelia. Incubation of P. aeruginosa with aGM1 reduced its binding, as did treatment of the epithelia with the tetrasaccharide moiety of this ganglioside (Gal beta 1-3GalNAc beta 1-4Gal beta 1-4Glc). Finally, an antibody to aGM1 effectively displaced P. aeruginosa from its binding site and blocked binding of S. aureus to CF cells but not to rescued cells. These results show that the tetrasaccharide of aGM1 is a receptor for P. aeruginosa and S. aureus and that its increased abundance in the apical membrane of CF epithelia makes it a likely contributor to the pathogenesis of bacterial infections in the CF lung.     

Multiple of isolates of Pseudomonas aeruginosa with differing antimicrobial susceptibility patterns from patients with cystic fibrosis.

Clinical isolates of Pseudomonas aeruginosa from patients with cystic fibrosis were studied in an effort to determine the unique characteristics of the infecting strains and to elucidate the pattern of colonization. Of 413 patients studied, 81% were chronically infected with P. aeruginosa. Patients from whom P. aeruginosa was never or only occasionally isolated were in better clinical condition than the chronically infected patients. Isolates were classified into six morphologic varieties: classic, rough, mucoid, gelatinous, dwarf, and enterobacter. Most patients had two or more of these varieties. Such multiple varieties from the same individual were of the same serotype but often differed in antibiotic susceptibility as determined by both the disk and the minimal inhibitory concentration methods. These differences were apparent when mucoid strains were compared with nonmucoid strains and when nonmucoid strains were compared with one another. Studies of antibiotic susceptibility should be performed on each morphologically different type of P. aeruginosa obtained from patients with cystic fibrosis.     

Effects of postural drainage, incorporating the forced expiration technique, on pulmonary function in cystic fibrosis

Detailed pulmonary function tests were performed on 12 patients with cystic fibrosis (CF) before and after 3 days treatment with postural drainage incorporating the forced expiration technique. The results following treatment showed a statistically significant improvement in FEV1 (P less than 0.001), FVC (P less than 0.001), PEFR(P less than 0.001), PIFR (P less than 0.001), and VEmax50 (P less than 0.025). The study demonstrates objective benefit from this form of physiotherapy in cystic fibrosis patients with copious bronchial secretions.     

Pseudomonas aeruginosa lipid A diversity and its recognition by Toll-like receptor 4

Lipid A is the pro-inflammatory component of bacterial lipopolysaccharide, the major surface component of Gram-negative bacteria. Gram-negative bacteria alter the structure of lipid A in response to specific environmental conditions including those found upon colonization of a host. The opportunistic pathogen Pseudomonas aeruginosa synthesizes a unique hexa-acylated lipid A containing palmitate and aminoarabinose during adaptation to the cystic fibrosis airway. Different lipid A species are observed in P. aeruginosa isolated from non-cystic fibrosis associated infections. Here we report that P. aeruginosa isolates from the airway of a cystic fibrosis patient with severe pulmonary disease synthesized a novel hepta-acylated lipid A. Cystic fibrosis-specific P. aeruginosa lipid A modifications result in resistance to host antimicrobial peptides and increased recognition by human Toll-like receptor 4 (TLR4). Using P. aeruginosa lipid A with different levels of acylation, we identified a 222 amino acid region in the extracellular portion of human TLR4 that is required for the differential recognition of cystic fibrosis-specific lipid A. P. aeruginosa adaptation to the human airway may, therefore, play a fundamental role in the progressive lung damage associated with cystic fibrosis.     

Endothelial nitric oxide synthase variants in cystic fibrosis lung disease

Variants in the genes encoding for the nitric oxide synthases may act as disease modifier loci in cystic fibrosis, affecting both an individual's nitric oxide level and pulmonary function. In this study, the 894G/T variant in exon 7 of the endothelial nitric oxide synthase gene was related to exhaled nitric oxide and pulmonary function in 70 cystic fibrosis patients who were aged 14.8 +/- 6.9 years (mean +/- SD), with a FEV1 of 69.4 +/- 24.8% predicted. Although there was no association between endothelial nitric oxide synthase genotypes and exhaled nitric oxide in males, nitric oxide levels were significantly higher in female cystic fibrosis patients with an 894T mutant allele, compared with female patients homozygous for the 894G wild-type allele (7.0 +/- 4.4 versus 3.6 +/- 1.9 parts per billion, p = 0.02). Furthermore, in female patients, colonization of airways with Pseudomonas aeruginosa was significantly (p < 0.05) less frequent when carrying an 894T mutant allele as compared with wild type. These data suggest that the 894T variant in the endothelial nitric oxide synthase gene is associated with increased airway nitric oxide formation in female cystic fibrosis patients, possibly affecting colonization of airways with P. aeruginosa.     

Hypersecretion of zymogen granules in the pathogenesis of cystic fibrosis

In the submandibular saliva of 10 cystic fibrosis subjects and 10 controls the turbidity and elevated calcium, protein, and amylase concentrations of the cystic fibrosis secretions, and precipitation of calcium and phosphate in a ratio consistent with hydroxyapatite have been confirmed. By electron microscopy the centrifuged deposits of the cystic fibrosis saliva were seen to be composed predominantly of round or oval subcellular corpuscles. By comparison with submandibular gland, these corpuscles have been identified as inclusion bodies (spherules) from within zymogen granules. Hydroxyapatite crystals formed on standing in the cystic fibrosis saliva. Polyacrylamide gel disc electrophoresis of the cystic fibrosis centrifuged deposits showed five bands, one of which, band 4, was more prominent in the deposit than in the supernatant gels.Comparisons have been made between these results and other studies and have shown (1) elevated calcium and protein in cystic fibrosis exocrine secretions; (2) simultaneous secretion of calcium and enzymes from salivary glands, stomach, and pancreas; and (3) increased salivary secretion of calcium and protein in response to parasympathomimetic and sympathomimetic drugs.Hypersecretion of calcium-containing zymogen granules is postulated as the cause of obstruction in cystic fibrosis.     

Antibody response to Burkholderia cepacia in patients with cystic fibrosis colonized with Burkholderia cepacia and Pseudomonas aeruginosa

INTRODUCTION: This study was designed to determine the relationship between formation of serum antibodies to lipopolysaccharide (LPS) core antigen of Burkholderia cepacia and pulmonary colonization with B. cepacia and Pseudomonas aeruginosa in patients with cystic fibrosis (CF), and to define if an enhanced host humoral immune response to B. cepacia was related to a poor clinical outcome. METHODS: Serum IgG to B. cepacia LPS core antigen was measured in adult cystic fibrosis patients colonized with B. cepacia and P. aeruginosa, and serial titres were measured in 13 B. cepacia and 41 P. aeruginosa colonized patients followed prospectively over 18 months. RESULTS: The median B. cepacia antibody titre was significantly greater in the patients colonized with B. cepacia compared to those colonized with P. aeruginosa, a group which grew B. cepacia intermittently from their sputum. and nine healthy controls. The median antibody titre at recruitment into the study was significantly greater in patients who later went into exacerbations compared with those who remained clinically stable. but there was no difference between B. cepacia antibody titres in patients who died and those who survived the study duration. DISCUSSION: The degree of overlap of serum IgG levels to B. cepacia LPS core antigen in cystic fibrosis patients colonized with B. cepacia and P. aeruginosa does not allow this antibody to be used in a clinical context to define infection status. The magnitude of the humoral response to B. cepacia may influence occurrence of pulmonary exacerbations, but a more exuberant humoral immune response to B. cepacia core LPS is not the mechanism by which pulmonary deterioration occurs.