Cystic fibrosis: a review of pulmonary infections and interventions

Molecular detection of CF lung pathogens: current status and future potential

Molecular diagnostic tests, based on the detection and identification of nucleic acids in human biological samples, are increasingly employed in the diagnosis of infectious diseases and may be of future benefit to CF microbiology services. Our growing understanding of the complex polymicrobial nature of CF airway infection has highlighted current and likely future shortcomings in standard diagnostic practices. Failure to detect fastidious or slow growing microbes and misidentification of newly emerging pathogens could potentially be addressed using culture-independent molecular technologies with high target specificity. This review considers existing molecular diagnostic tests in the context of the key requirements for an envisaged CF microbiology focussed assay. The issues of assay speed, throughput, detection of multiple pathogens, data interpretation and antimicrobial susceptibility testing are discussed.

Infections in chronic lung diseases

Chronic lung diseases are prevalent worldwide and cause significant mortality and suffering. This article discusses infections that occur in three chronic lung diseases: chronic obstructive pulmonary disease, bronchiectasis, and cystic fibrosis. Rather than discussing the role of infections as etiology of these diseases, this article focuses on infections that occur in the background of established chronic lung disease.

The cystic fibrosis transmembrane conductance regulator gene and ion channel function in patients with idiopathic pancreatitis

Cystic fibrosis transmembrane conductance regulator (CFTR) gene mutations are associated with cystic fibrosis (CF)-related monosymptomatic conditions, including idiopathic pancreatitis. We evaluated prospectively enrolled patients who had idiopathic recurrent acute pancreatitis or idiopathic chronic pancreatitis, healthy controls, CF heterozygotes, and CF patients (pancreatic insufficient or sufficient) for evidence of CFTR gene mutations and abnormalities of ion transport by sweat chloride and nasal potential difference testing. DNA samples from anonymous blood donors were controls for genotyping. At least one CFTR mutation or variant was carried in 18 of 40 patients (45%) with idiopathic chronic pancreatitis and in 6 of 16 patients (38%) with idiopathic recurrent acute pancreatitis but in only 11 of the 50 controls (22%, P=0.005). Most identified mutations were rare and would not be identified in routine genetic screening. CFTR mutations were identified on both alleles in six patient (11%). Ion transport measurements in patients with pancreatitis showed a wide range of results, from the values in patients with classically diagnosed CF to those in the obligate heterozygotes and healthy controls. In general, ion channel measurements correlated with the number and severity of CFTR mutations. Twelve of 56 patients with pancreatitis (21%) fulfilled current clinical criteria for the diagnosis of CF, but CFTR genotyping alone confirmed the diagnosis in only two of these patients. We concluded that extensive genotyping and ion channel testing are useful to confirm or exclude the diagnosis of CF in the majority of patients with idiopathic pancreatitis.

Differential immune modulatory activity of Pseudomonas aeruginosa quorum-sensing signal molecules

Pseudomonas aeruginosa releases a spectrum of well-regulated virulence factors, controlled by intercellular communication (quorum sensing) and mediated through the production of small diffusible quorum-sensing signal molecules (QSSM). We hypothesize that QSSM may in fact serve a dual purpose, also allowing bacterial colonization via their intrinsic immune-modulatory capacity. One class of signal molecule, the N-acylhomoserine lactones, has pleiotropic effects on eukaryotic cells, particularly those involved in host immunity. In the present study, we have determined the comparative effects of two chemically distinct and endobronchially detectable QSSM, N-(3-oxododecanoyl)-L-homoserine lactone (3-oxo-C12-HSL) and 2-heptyl-3-hydroxy-4 (1H)-quinolone or the Pseudomonas quinolone signal (PQS), on human leukocytes exposed to a series of stimuli designed to detect differential immunological activity in vitro. 3-Oxo-C12-HSL and PQS displayed differential effects on the release of interleukin-2 (IL-2) when human T cells were activated via the T-cell receptor and CD28 (a costimulatory molecule). 3-Oxo-C12-HSL inhibited cell proliferation and IL-2 release; PQS inhibited cell proliferation without affecting IL-2 release. Both molecules inhibited cell proliferation and the release of IL-2 following mitogen stimulation. Furthermore, in the presence of Escherichia coli lipopolysaccharide, 3-oxo-C12-HSL inhibited tumor necrosis factor alpha release from human monocytes, as reported previously (K. Tateda et al., Infect. Immun. 64:37-43, 1996), whereas PQS did not inhibit in this assay. These data highlight the presence of two differentially active immune modulatory QSSM from P. aeruginosa, which are detectable endobronchially and may be active at the host/pathogen interface during infection with P. aeruginosa, should the bronchial airway lymphoid tissues prove to be accessible to QSSM.

Pathophysiology and management of pulmonary infections in cystic fibrosis

This comprehensive State of the Art review summarizes the current published knowledge base regarding the pathophysiology and microbiology of pulmonary disease in cystic fibrosis (CF). The molecular basis of CF lung disease including the impact of defective cystic fibrosis transmembrane regulator (CFTR) protein function on airway physiology, mucociliary clearance, and establishment of Pseudomonas aeruginosa infection is described. An extensive review of the microbiology of CF lung disease with particular reference to infection with P. aeruginosa is provided. Other pathogens commonly associated with CF lung disease including Staphylococcal aureus, Burkholderia cepacia, Stenotrophomonas maltophilia, Achromobacter xylosoxidans and atypical mycobacteria are also described. Clinical presentation and assessment of CF lung disease including diagnostic microbiology and other measures of pulmonary health are reviewed. Current recommendations for management of CF lung disease are provided. An extensive review of antipseudomonal therapies in the settings of treatment for early P. aeruginosa infection, maintenance for patients with chronic P. aeruginosa infection, and treatment of exacerbation in pulmonary symptoms, as well as antibiotic therapies for other CF respiratory pathogens, are included. In addition, the article discusses infection control policies, therapies to optimize airway clearance and reduce inflammation, and potential future therapies.

Molecular typing of the bacterial flora in sputum of cystic fibrosis patients

Despite recent advances in therapy, lower airway infections remain the major cause of morbidity and mortality in cystic fibrosis (CF) patients. Bacterial colonisation of the lower airways in CF is limited to a few bacterial species, commonly Staphylococcus aureus, Pseudomonas aeruginosa and Haemophilus influenzae. Burkholderia cepacia colonisation is much rarer, but it has been thought to be associated with more advanced lung disease and increased mortality. A rapid characterisation of the bacterial flora in sputum of CF patients is of great importance for proper treatment. The aim of this study was to establish bacterial profiles and to identify pathogenic bacteria in respiratory specimens by means of molecular methods including temporal temperature gradient gel electrophoresis (TTGE) and DNA sequencing of PCR amplicons derived from 16S rDNA variable V3 and V6 regions. Sputa of 13 CF patients (7 males/6 females, age 19-59 years) collected at the Stockholm CF centre were analysed. TTGE revealed the presence of complex bacterial profiles in all samples. The V3 and V6 PCR amplicons were cloned and sequenced by real-time DNA Pyrosequencing. DNA from Staphylococcus aureus, Haemophilus influenzae, and Pseudomonas aeruginosa, respectively, was identified together with sequences from normal oral cavity flora. The results were in reasonable agreement with those obtained by conventional bacterial culture, considering that only known CF pathogens are included in routine reports. However, the methodology seems too elaborate to be introduced into daily routine

Towards the pharmacogenomics of cystic fibrosis

Cystic fibrosis (CF) is the most common lethal recessive genetic disease affecting children in Europe and the US. CF is a multiorgan disease and may present a variety of clinical symptoms, like chronic obstructive lung disease, exocrine pancreatic insufficiency (PI) and elevated sweat chloride concentration. CF mutations have also been found in other related clinical diseases such as congenital bilateral absence of the vas deferens (CBAVD), disseminated bronchiectasis and chronic pancreatitis. These clinical overlaps pose etiopathogenetic, diagnostic and therapeutic questions. Despite stunning advances in genomic technologies and drug discovery, drug therapy often improves disease symptoms but does not cure the disease. One of the main causes of this failure in CF cure may be attributable to genetic variability and to the scarce knowledge of CF biochemistry. Therefore, knowing the genotype of a patient might help improve drug efficacy, reduce toxicity and suggests innovative genomic-based therapy approaches.

Dynamics of bacterial colonisation in the respiratory tract of patients with cystic fibrosis

Mutations in the human genome may result in altered phenotypes. The cystic fibrosis (CF) patient, for instance, suffers from an aberrant composition of the epithelial lining of the gastrointestinal and respiratory tract. In this particular case, a single point mutation in the cystic fibrosis conductance regulator (CFTR) gene results in major physiological changes resulting in ecological changes that generate a niche particularly attractive to a selected set of microbial pathogens. We here present a review on the dynamics of the bacterial populations inhabiting the CF lung. Studies focusing on Staphylococcus aureus, Haemophilus influenzae and Pseudomonas aeruginosa will be summarised and discussed, whereas the technology used for microbial characterisation will be shortly highlighted. Emphasis, however, will be on those studies that assessed the genetic diversity among clinical isolates that were obtained over prolonged periods of time, enabling the distinction between persistent colonisation versus frequent re-infection by the selected pathogens. Evolutionary adaptation of pathogens to the CF lung is a common theme in many of these studies.

Characterization of alginate lyase from Pseudomonas syringae pv. syringae

The gene encoding alginate lyase (algL) in Pseudomonas syringae pv. syringae was cloned, sequenced, and overexpressed in Escherichia coli. Alginate lyase activity was optimal when the pH was 7.0 and when assays were conducted at 42 degrees C in the presence of 0.2 M NaCl. In substrate specificity studies, AlgL from P. syringae showed a preference for deacetylated polymannuronic acid. Sequence alignment with other alginate lyases revealed conserved regions within AlgL likely to be important for the structure and/or function of the enzyme. Site-directed mutagenesis of histidine and tryptophan residues at positions 204 and 207, respectively, indicated that these amino acids are critical for lyase activity.

Clinical use of fluoroquinolones in children

OBJECTIVE

To review the pharmacokinetics, efficacy, and safety of fluoroquinolones in children.

DATA SOURCES

A MEDLINE search (January 1966-March 1998) was conducted for relevant literature.

STUDY SELECTION AND DATA EXTRACTION

Data from compassionate use and published studies were reviewed for the assessment of pharmacokinetics, efficacy, and safety of fluoroquinolones in children.

DATA SYNTHESIS

Fluoroquinolones have a broad spectrum coverage of gram-positive and gram-negative bacteria, including Pseudomonas aeruginosa and intracellular organisms. Fluoroquinolones are well absorbed from the gastrointestinal tract, have excellent tissue penetration, low protein binding, and long elimination half-lives. These antibiotics are effective in treating various infections and are well tolerated in adults. However, the use of fluoroquinolones in children has been restricted due to potential cartilage damage that occurred in research with immature animals. Fluoroquinolones have been used in children on a compassionate basis. Ciprofloxacin is the most frequently used fluoroquinolone in children, most often in the treatment of pulmonary infection in cystic fibrosis as well as salmonellosis and shigellosis. Other uses include chronic suppurative otitis media, meningitis, septicemia, and urinary tract infection. Safety data of fluoroquinolones in children appear to be similar to those in adults. Fluoroquinolones are associated with tendinitis and reversible arthralgia in adults and children. However, direct association between fluoroquinolones and arthropathy remains uncertain.

CONCLUSIONS

Fluoroquinolones have been found to be effective in treating certain infections in children. Additional research is needed to define the optimal dosage regimens in pediatric patients. Although fluoroquinolones appear to be well tolerated, further investigations are needed to determine the risk of arthropathy in children. However, their use in children should not be withheld when the benefits outweigh the risks.

Diagnosis of cystic fibrosis: Indian perspective

Cystic fibrosis (CF) is one of the common life limiting inherited diseases in Caucasian population. Recent reports suggest that the diagnosis of cystic fibrosis in Indian children is missed or delayed due to low index of suspicion. The diagnosis of cystic fibrosis is suspected by the typical clinical features and should be confirmed by doing sweat chloride estimation. If sweat test is not available, ancillary tests including blood electrolyte and acid base balance, airway microbiology, tests to identify pancreatic insufficiency and semen analysis for obstructive azoospermia in post pubertal boys should be carried out. Positive results of these tests make the suspicion very strong. A strongly suspected case should be treated as cystic fibrosis, but for giving a diagnosis of CF, sweat test should be done from the nearest centre where it is available. In the presence of typical clinical features with borderline sweat chloride values sweat test should be repeated 2-3 times and the child should be investigated for alternative diagnosis. In the absence of alternative diagnosis with consistently high or borderline sweat chloride values an attempt should be made to get tests for mutations.

Crystal structure of alginate lyase A1-III from Sphingomonas species A1 at 1.78 A resolution

The three-dimensional structure of alginate lyase A1-III (ALYIII) from a Sphingomonas species A1 was determined by X-ray crystallography. The enzyme was crystallized by the hanging-drop vapour-diffusion method in the presence of 49% ammonium sulfate at 20 degrees C. The crystals are monoclinic and belong to the space group C2 with unit cell dimensions of a=49.18 A, b=93.08 A, c=82.10 A and beta=104.12 degrees. There was one molecule of alginate lyase in the asymmetric unit of the crystal. The diffraction data up to 1. 71 A were collected with Rsymof 5.0%. The crystal structure of ALYIII was solved by the multiple isomorphous replacement method and refined at 1.78 A resolution using X-PLOR with a final R -factor of 18.0% for 10.0 to 1.78 A resolution data. The refined model of ALYIII contained 351 amino acid residues, 299 water molecules and two sulfate ions. The three-dimensional structure of ALYIII was abundant in helices and had a deep tunnel-like cleft in a novel (alpha6/alpha5)-barrel structure, which was similar to the (alpha6/alpha6)-barrel found in glucoamylase and cellulase. This structure presented the possibility that alginate molecules might penetrate into the cleft to interact with the catalytic site of ALYIII.

Quantitation of inflammatory responses to bacteria in young cystic fibrosis and control patients

Recent studies suggest that inflammation plays a role in the pathogenesis of lung disease in cystic fibrosis (CF). The goal of the present study was to quantitatively compare bronchoalveolar lavage fluid (BALF) inflammation and its relation to bacterial infection, between children with CF and children with other chronic respiratory problems. Differential cell counts, immunoreactive interleukin 8 (IL-8), and quantitative bacterial cultures were done in BALF from 54 CF (median age 1.8 yr) and 55 control patients (median age 1.0 yr) who underwent bronchoscopy for clinical indications. Among infected CF patients, those with Pseudomonas aeruginosa did not have more inflammation than those without P. aeruginosa. The ratio of neutrophils or of IL-8 to bacteria in BALF was significantly greater for CF patients compared with control subjects, regardless of pathogen. Calculation of linear regression for either neutrophils or IL-8, as a function of bacterial quantity, yielded positive slopes for both CF and control patients, but with significant elevations for CF. We conclude that the inflammatory response to bacterial infection is increased or prolonged in CF compared with control patients, and that this increase is not necessarily due to pathogens specific for CF (e.g., P. aeruginosa). These data may provide further rationale for anti-inflammatory therapy early in CF.

Reduced interleukin-8 production by cystic fibrosis airway epithelial cells

The acquisition of Pseudomonas aeruginosa in the airways of patients with cystic fibrosis (CF) is the initial event leading to bronchiectasis and lung disease. Although the host factors that permit initial airway colonization are largely unknown, recent studies suggest that secretion of interleukin (IL)-8 by airway epithelia and local recruitment of neutrophils is the final pathway in a pulmonary cytokine network. To determine whether differences in cytokine production exist between normal and CF airway epithelia, secretion of immunoreactive IL-8 and IL-10 as well as specific messenger RNA (mRNA) abundance were compared in airway epithelia expressing normal and mutant CF transmembrane regulator. After induction with IL-1beta, a CF airway cell line engineered to express the wild-type CF gene (CFT1-LCFSN) secreted significantly more immunoreactive IL-8 than did its isogenic parent that expressed the mutant CF gene (CFT1) or an isogenic vector control line (CFT1-LC3). Further studies with the three related cell lines demonstrated that expression of CFT1-LCFSN was associated with a significant increase in uninduced secretion of immunoreactive IL-8 as well as a 10- to 20-fold increase in IL-8 mRNA abundance when compared with the isogenic lines expressing the mutant gene. IL-1beta induction and intracellular accumulation of IL-8 appeared to be unaffected by CF genotype. These studies suggest that IL-8 secretion by CF airway epithelial cells is defective and may contribute to Pseudomonas persistence in the CF airway. Further studies are needed to confirm this difference in other cell lines and determine the linkage between IL-8 production and CF gene expression.

Impact of microbiology practice on cumulative prevalence of respiratory tract bacteria in patients with cystic fibrosis

Investigators participating in the Epidemiologic Study of Cystic Fibrosis project began to collect microbiological, pulmonary, and nutritional data on cystic fibrosis (CF) patients at 180 North American sites in 1994. Part of this study was a survey undertaken in August 1995 to determine microbiology laboratory practices with regard to pulmonary specimens from CF patients. The survey included a section on test ordering, completed by a site clinician, and a section on test performance and reporting, completed by each site's clinical microbiology laboratory staff. Seventy-nine percent of the surveys were returned. There was intersite consistency of microbiology laboratory practices in most cases. The majority of sites follow most of the CF Foundation consensus conference recommendations. There were differences in the frequency at which specimens for culture were obtained, in the use of selective media for Staphylococcus aureus and Haemophilus influenzae, and in the use of a prolonged incubation for Burkholderia cepacia. These variations in practice contribute to prevalence differences among sites and may result in differences in clinical care.

Effects of ion composition and tonicity on human neutrophil antibacterial activity

Infants with cystic fibrosis (CF) often are infected with Staphylococcus aureus (S. aur.), which is followed by colonization with Pseudomonas aeruginosa (P. aerug.). In spite of an excessive, neutrophil-dominated inflammatory response in the respiratory tract, patients with CF often succumb to pulmonary infections with P. aerug. Because peripheral blood neutrophils of these patients have normal functions, we examined whether hypothesized alterations of the airway surface liquids (ASL) in these patients significantly impair neutrophil bactericidal activity in the microenvironment of the CF lung. The ionic composition of CF ASL is still not entirely defined and has been speculated to be abnormally high or abnormally low in Na+ and Cl- concentrations; estimates of osmolarities have ranged from 200 (hypo-osmolar) to 285 (iso-osmolar) to > 300 meq/L (hyper-osmolar). Our data indicate that bacterial killing activity of human peripheral blood neutrophils against P. aerug. or S. aur. is not decreased in buffers in which NaCl was replaced with equimolar concentrations of choline Cl, KCl, or N-methyl-D-glucamine chloride to maintain isotonicity. Amiloride or benzamil, known modulators of Na+ transport in neutrophils, did not interfere with this neutrophil function. Deviations from isotonicity of +/- 50% also failed to diminish bactericidal activity of neutrophils significantly. In contrast, superoxide production and enzyme secretion in response to the chemotactic peptide N-formylmethionylleucylphenylalanine appeared to be sensitive to the ionic milieu of the assay buffers. Our results suggest that the postulated alterations in the ionic composition of ASL in CF lungs are insufficient to explain why neutrophils fail to clear infections with P. aerug. in these patients.

What is a cystic fibrosis diagnosis?

Cystic fibrosis (CF) should be considered in patients with a wide variety of clinical presentations and of diverse racial and ethnic backgrounds. In most cases the diagnosis is suggested by manifestations of chronic sinopulmonary disease and exocrine pancreatic insufficiency, and then confirmed by a positive sweat test result. Patients may, however, present with pancreatic sufficiency or other atypical clinical features, sometimes in association with normal or borderline sweat test results. In such cases, the ability to detect CF mutations and to measure transepithelial bioelectric properties can be diagnostically useful. Mutation analysis can also be used for carrier screening, prenatal diagnosis, and newborn screening.

Alginate lyase promotes diffusion of aminoglycosides through the extracellular polysaccharide of mucoid Pseudomonas aeruginosa

We demonstrated that a 2% suspension of Pseudomonas aeruginosa alginate completely blocked the diffusion of gentamicin and tobramycin, but not that of carbenicillin, illustrating how alginate production can help protect P. aeruginosa growing within alginate microcolonies in patients with cystic fibrosis (CF) from the effects of aminoglycosides. This aminoglycoside diffusion barrier was degraded with a semipurified preparation of P. aeruginosa alginate lyase, suggesting that this enzyme deserves consideration as an adjunctive agent for CF patients colonized by mucoid strains of P. aeruginosa.

The diagnosis of cystic fibrosis: a consensus statement. Cystic Fibrosis Foundation Consensus Panel

The diagnostic criteria proposed here are not likely to cover every possible clinical scenario, and there will be clinical dilemmas. For the vast majority of patients with CF, the diagnosis will be suggested by the presence of one or more characteristic clinical features, a history of CF in a sibling, or a positive newborn screening test result and will then be confirmed by laboratory evidence of CFTR dysfunction (Table V). Abnormal CFTR function will usually be documented by two elevated sweat chloride concentrations obtained on separate days or identification of two CF mutations. For patients in whom sweat chloride concentrations are normal or borderline and in whom two CF mutations are not identified, an abnormal nasal PD measurement recorded on 2 separate days can be used as evidence of CFTR dysfunction. Clinical judgment will continue to be essential in patients who have typical or "atypical" clinical features but who lack conclusive evidence of CFTR dysfunction. Such patients will require close clinical follow-up along with laboratory reevaluation as appropriate.

Creatinine clearance as predictor of tobramycin elimination in adult patients with cystic fibrosis

Assessment of renal function and relating this parameter to amino-glycoside clearance is important for an appropriate individualization of dosage regimens in patients with impaired renal function. However, it has been suggested that in cystic fibrosis (CF), creatinine clearance (CrCl) is not a good predictor of tobramycin clearance because of a lack of correlation. The aim of this study was to investigate the correlation between the tobramycin clearance and the measured CrCl. In addition, because most pharmacokinetic computer models use an a priori relationship between CrCl and tobramycin elimination rate constant [k(el)], regression analysis of k(el) on CrCl was performed. Eighteen CF patients (12 men, 6 women, ages 21-55 years) were treated with intravenous tobramycin. Blood and urine samples were collected for tobramycin analysis and determination of the CrCl. For each patient, CrCl was also estimated using the formulas of Cockcroft and Gault (C/G), Jelliffe I (J I), and Jelliffe II (J II). Predictive performance of these formulas was evaluated using mean error and mean squared error as reflections of bias and precision. Tobramycin total body clearance as well as renal clearance correlated significantly with CrCl (r = 0.52; p = 0.02 and r = 0.78; p = 0.02, respectively). Regression of the tobramycin k(el) versus CrCl gave the following equation: k(el) = 0.135 + 0.00134*CrCl/1.73 m2 (r = 0.64; p = 0.004). The 95% confidence interval of intercept and slope of the regression line were 0.019-0.251 and 0.00049-0.00219, respectively. The formulas of C/G, J I, and J II all overpredicted CrCl. Bias was 19, 24, and 8 ml/min, and precision was 37, 42, and 33 ml/min, respectively, for the C/G, J I, and J II formulas. In our CF population the J II formula gave the best estimation of the CrCl but calculated estimates deviated -25(-)+62% from measured values.

Prospective evaluation of a dose prediction algorithm for intravenous tobramycin in adolescent and adult patients with cystic fibrosis

The predictive performance of a new algorithm to calculate the initial daily dose of tobramycin in patients with cystic fibrosis (CF) was prospectively evaluated. Twenty-six patients with CF (15 men, 11 women, 18-45 years of age) with an acute exacerbation of their chronic pulmonary infection were treated with intravenous tobramycin. The initial dose was calculated with a previously presented algorithm. This algorithm was derived from correlation analysis performed on the adjusted daily dose guided by the determination of serum concentrations: dose (mg three times daily) = 90 + 2.13 x LBM (kg), where LBM (male) = (1.1 x body weight [BW]) - (128 x BW2/height2) and LBM (female) = (1.07 x BW) - (148 x BW2/height2). The predictive performance of this algorithm was evaluated comparing the calculated initial daily dose with the adjusted daily dose for peak and trough levels of 9-11 mg/L and 1.0 mg/L, respectively. Mean squared error and mean error were determined as reflections of precision and bias. The predictive performance of the algorithm was compared with historical data on the predictive performance of the standard equation to dose of 3.3 mg/kg body weight three times daily. The dose calculated with the algorithm proved to give peak serum concentrations in a narrower range and to have a greater precision, but bias was equal. Applying the algorithm, more patients had initial peak serum concentrations in the pre-determined range of 9-11 mg/L than when using the standard equation, so fewer dose adjustments had to be made.

Alginate synthesis in Pseudomonas aeruginosa: the role of AlgL (alginate lyase) and AlgX

Previous studies localized an alginate lyase gene (algL) within the alginate biosynthetic gene cluster at 34 min on the Pseudomonas aeruginosa chromosome. Insertion of a Tn501 polar transposon in a gene (algX) directly upstream of algL in mucoid P. aeruginosa FRD1 inactivated expression of algX, algL, and other downstream genes, including algA. This strain is phenotypically nonmucoid; however, alginate production could be restored by complementation in trans with a plasmid carrying all of the genes inactivated by the insertion, including algL and algX. Alginate production was also recovered when a merodiploid that generated a complete alginate gene cluster on the chromosome was constructed. However, alginate production by merodiploids formed in the algX::Tn501 mutant using an alginate cluster with an algL deletion was not restored to wild-type levels unless algL was provided on a plasmid in trans. In addition, complementation studies of Tn501 mutants using plasmids containing specific deletions in either algL or algX revealed that both genes were required to restore the mucoid phenotype. Escherichia coli strains which expressed algX produced a unique protein of approximately 53 kDa, consistent with the gene product predicted from the DNA sequencing data. These studies demonstrate that AlgX, whose biochemical function remains to be defined, and AlgL, which has alginate lyase activity, are both involved in alginate production by P. aeruginosa.

Association between transcript levels of the Pseudomonas aeruginosa regA, regB, and toxA genes in sputa of cystic fibrosis patients

In this study, we examined the regulation of exotoxin A (ETA) production by Pseudomonas aeruginosa during chronic lung infections of cystic fibrosis (CF) patients. We used a recently developed technique termed population transcript accumulation in hybridization studies with RNA extracted from sputa. With this technique, we demonstrated that the structural gene for ETA, toxA, as well as two genes encoding positive regulators of ETA synthesis, regA and regB, were expressed in the lungs of CF patients infected with P. aeruginosa. These genes were always expressed together, never alone or in pairs, suggesting coincident expression and a possible regulatory role for regA and regB in this environment. Fluctuations in the levels of the three gene products were observed among samples, consistent with a regulatory phenomenon. The level of regB RNA detected never exceeded that of regA, although the ratio of regA RNA to regB RNA detected did change between samples. These observations are in agreement with in vitro observations which have shown that regB is located 3' to regA in an operon which is expressed from two independently regulated promoters located upstream of regA. The presence of high levels of toxA, regA, and regB RNAs in some sputum samples prompted us to look for hyperproducing-toxin strains in the sputa of CF patients. In vitro, one such strain, 4384, had a transcript accumulation pattern for toxA, regA, and regB similar to that of a laboratory hyperproducer of ETA, strain PA103. These observations suggest that regA and regB are involved in the regulation of ETA production in strains of P. aeruginosa infecting the lungs of CF patients and that some of these strains may regulate ETA production in a manner similar to that of the hyperproducing-ETA strain PA103.

Experience with pediatric lung transplantation

Heart-lung transplantation and lung transplantation have become accepted techniques in adult patients with end-stage cardiopulmonary disease. We report here our experience between July 1985 and March 1993 with 34 children (< 20 years) who underwent heart-lung (n = 18) or lung transplantation (n = 17). Indications for transplantation included cystic fibrosis (n = 9), congenital heart disease with Eisenmenger complex (n = 9), primary pulmonary hypertension (n = 8), pulmonary arteriovenous malformations (n = 2), desquamative interstitial pneumonia (n = 2), Proteus syndrome with multicystic pulmonary disease (n = 1), graft-versus-host disease (n = 1), rheumatoid lung disease (n = 1), and bronchiolitis obliterans and emphysema (n = 1). Twenty-six patients (76%) have survived from 1 to 88 months after transplantation; most patients have returned to an active lifestyle. Of the eight deaths, four were due to infections, two to multiorgan failure, 1 to posttransplant lymphoproliferative disease, and one to donor organ failure. Four of the patients who died had cystic fibrosis. Despite considerable morbidity related to infection, rejection, and function of the heart-lung and lung allograft in some patients, our results with this potentially lifesaving procedure in the pediatric population have been encouraging.

Predictive value of pulmonary function testing during pulmonary exacerbations in cystic fibrosis

The optimal duration of therapy for acute exacerbations of cystic fibrosis (CF) has not been defined, and the utility of serial pulmonary function testing in predicting the duration of therapy has yet to be established. In a review of 90 pulmonary exacerbations of 39 patients with CF requiring hospitalization, we found that 72% of the patients recovered following 2 weeks of intravenous antibiotics and aggressive chest physiotherapy, and that 28% required an extended third week of therapy. Recovery was delayed in patients with more severe chronic pulmonary disease, but the rate of improvement was independent of the degree of pulmonary deterioration with the acute exacerbation. A 40% recovery of FEV1 at 1 week was found to correlate significantly with the duration of hospitalization in the 90 patients. When prospectively applied to a second series of consecutively hospitalized patients with CF, 25/28 patients admitted for 2 weeks demonstrated > 40% improvement in FEV1 at 1 week, as compared to 5/10 patients subsequently treated for > or = 3 weeks (P = 0.030). The predictive values for 2- or 3-week hospitalizations with 1-week interval recovery of > 40% or < or = 40% in FEV1 were 79% and 62%, respectively. These findings suggest that the response to intensive therapy in CF exacerbations is variable and that improvements in pulmonary function after 1 week of therapy may be used to predict the subsequent duration of therapy in the majority of CF patients with pulmonary exacerbations.

Characterization of the Pseudomonas aeruginosa alginate lyase gene (algL): cloning, sequencing, and expression in Escherichia coli

Mucoid strains of Pseudomonas aeruginosa produce a viscous exopolysaccharide called alginate and also express alginate lyase activity which can degrade this polymer. By transposon mutagenesis and gene replacement techniques, the algL gene encoding a P. aeruginosa alginate lyase enzyme was found to reside between algG and algA within the alginate biosynthetic gene cluster at 35 min on the P. aeruginosa chromosome. DNA sequencing data for algL predicted a protein product of ca. 41 kDa, including a 27-amino-acid signal sequence, which would be consistent with its possible localization in the periplasmic space. Expression of the algL gene in Escherichia coli cells resulted in the expression of alginate lyase activity and the appearance of a new protein of ca. 39 kDa detected on sodium dodecyl sulfate-polyacrylamide gels. In mucoid P. aeruginosa strains, expression of algL was regulated by AlgB, which also controls expression of other genes within the alginate gene cluster. Since alginate lyase activity is associated with the ability to produce and secrete alginate polymers, alginate lyase may play a role in alginate production.

Population transcript accumulation of Pseudomonas aeruginosa exotoxin A and elastase in sputa from patients with cystic fibrosis

The in vivo regulation of Pseudomonas aeruginosa virulence factors during the chronic lung infections associated with cystic fibrosis is poorly understood. We have developed an approach for the analysis of transcript accumulation of individual virulence factors from the P. aeruginosa populations found in the sputa of patients with cystic fibrosis. This method has been named population transcript accumulation, since we examine the transcript accumulation patterns in RNA extracted from the total bacterial population found in the sputum samples. DNA probes specific for P. aeruginosa elastase (lasB) and exotoxin A (toxA) were used to examine the population transcript accumulation of 21 sputum samples taken from 10 patients. We detected three patterns of population transcript accumulation: lasB and toxA, lasB alone, and neither lasB nor toxA. We also measured the relative levels of elastase and exotoxin A transcript accumulation in 19 of these samples. In the six samples containing both toxA and lasB transcripts, we found that the levels of lasB transcripts were consistently higher than those of toxA. Differences in the stability of the two mRNA species could not completely account for the higher level of lasB population transcript accumulation, since we showed that the mRNA half-life of lasB (11 min) was similar to that of toxA (10 min). Finally, we showed that elastase transcripts could be detected in some samples which contained only mucoid isolates. This finding suggests that both mucoid and nonmucoid populations may be transcribing lasB in the lungs of patients with cystic fibrosis.

Raised serum soluble interleukin-2 receptor concentrations in cystic fibrosis patients with and without evidence of lung disease

Soluble interleukin-2 receptor (sIL-2R-CD25) concentrations were measured in the sera of 115 children with cystic fibrosis and 45 aged matched controls. Above the age of 4 years children with cystic fibrosis had significantly raised concentrations irrespective of disease status as judged by Shwachman score, lung function, or evidence of pseudomonas colonisation. It is believed that these data indicate that T lymphocyte activation can be detected before there is clinical evidence of lung inflammation due to infection in cystic fibrosis. They support the notion that early use of anti-inflammatory (immunosuppressive) drugs may have a role in delaying the progress of lung damage in cystic fibrosis.

Comparison of serum amyloid A and C-reactive protein as indicators of lung inflammation in corticosteroid treated and non-corticosteroid treated cystic fibrosis patients

Serum amyloid A (SAA) and C-reactive protein (CRP) levels were compared in 830 serum samples from 155 cystic fibrosis (CF) patients. Correlation coefficients were calculated for all samples (r = 0.73), for samples from non-corticosteroid treated (CFNS) patients (n = 698, r = 0.80), and for samples from corticosteroid treated (CFS) patients (n = 132, r = 0.35). SAA was the more sensitive indicator of pulmonary inflammation when SAA and CRP were compared to pulmonary function tests of 49 hospitalized patients at admission and discharge. CRP levels were significantly (p less than .05) lower at admission in CFS patients than in CFNS patients, whereas SAA levels were not significantly different between the two groups. All nine CFS patients hospitalized had elevated SAA levels (average 22 times above normal limits) at admission, while only six had elevated CRP levels (average 3.7 times above normal limits) at admission. In the 40 CFNS patients both SAA and CRP levels were significantly elevated at admission. In each case SAA and CRP levels declined as pulmonary functions improved with effective antimicrobial therapy. In three instances SAA levels increased during hospitalization while CRP levels did not. In each case, rising SAA levels indicated clinical deterioration associated with evolving resistance of P. aeruginosa which required a change in antibiotic therapy.

Heterogeneity, persistence, and distribution of Pseudomonas aeruginosa genotypes in cystic fibrosis patients

A collection of 222 isolates of Pseudomonas aeruginosa was obtained from the respiratory tract of 16 patients with cystic fibrosis over a 4- to 9-month period. Fourteen of these patients were unrelated, while the remaining two were siblings. Isolates were typed by conventional pyocin typing and also by the use of a DNA probe containing 741 bp immediately upstream of the exotoxin A structural gene and the initial 732 bp of the exotoxin A structural gene. By pyocin typing, 69% (11 of 16) of the patients were shown to harbor a single type that persisted in the lung throughout the study. By genotyping (DNA probe typing), all but three patients (13 of 16, 81%) harbored a single persistent genotype in their lungs. Six patients other than the sibling pair (6 of 14, 43%) shared a common genotype in their lungs as judged by DNA probing, and the pyocin type of these isolates was also identical. In four of these six patients, the shared genotype was also the persistent genotype. The sibling pair studied also carried a common genotype in their lungs as indicated by DNA probing, even though the pyocin type of these isolates varied. Results presented suggest that the majority of patients harbor a persistent strain in their lungs and that cross-colonization may occur.

Ibuprofen in children with cystic fibrosis: pharmacokinetics and adverse effects

Antiinflammatory therapy with ibuprofen has been proposed to retard the progression of lund disease in cystic fibrosis (CF). The pharmacokinetics and toxicity of ibuprofen were investigated in a randomized, double-blind, placebo-controlled, 3-month dose-escalation study in 19 children with CF, 6 to 12 years of age. The subjects received orally and twice daily 300 mg of drug during the first month, 400 mg in the second month, and 600 mg in the third month. Ibuprofen pharmacokinetics and evaluation for adverse effects were performed at the beginning and end of each month. The dose of ibuprofen was increased if peak plasma concentration (Cmax) was less than 50 micrograms/ml. To preserve the blind nature of the study, the dose in matched subjects taking placebo was also increased. The subjects randomly assigned to receive ibuprofen (n = 13) completed 26 months of treatment; placebo subjects (n = 5) completed 12 months. With dose escalation, Cmax and the area under the concentration-time curve from zero to infinity significantly increased (p less than 0.01). The pharmacokinetics of ibuprofen in 13 children with CF who received 13.4 +/- 4.1 mg/kg (mean +/- SD) were compared with those in four healthy children who received a similar dose. Peak plasma concentration (48 +/- 17 micrograms/ml) was decreased by 27% (p = 0.06), the area under the concentration-time curve (6.1 +/- 1.7 mg.min/ml) was decreased by 46% (p less than 0.001), apparent total clearance (2.3 +/- 0.6 ml/min.kg-1) was increased by 77% (p less than 0.01), and apparent volume of distribution during terminal phase (291 +/- 91 ml/kg) was increased by 84% (p = 0.01) in the children with CF. Time to Cmax (66 +/- 20 minutes) and elimination half-life (92 +/- 27 minutes) were not significantly different. No subjects were withdrawn from the study because of side effects. No adverse effects could be attributed to ibuprofen. Thus ibuprofen administration has no significant toxic effects, but Cmax will need to be monitored for effective dosing in patients with CF.

Microbiology of airway disease in patients with cystic fibrosis

Individuals with cystic fibrosis have abbreviated life spans primarily due to chronic airway infection. A limited number of types of organisms are responsible for these infections, with Staphylococcus aureus and Pseudomonas aeruginosa being of primary importance. In the pre-antibiotic era, greater than 90% of deaths due to infection were caused by S. aureus and death usually occurred in the first 2 years of life. With the advent of effective antistaphylococcal therapy, life spans increased and P. aeruginosa became the pathogen of primary importance. P. aeruginosa isolates recovered from patients with cystic fibrosis have a unique phenotypic characteristic referred to as "mucoid." The mucoid phenotype is due to the production of a mucoid exopolysaccharide. A mucoid exopolysaccharide is believed to play a central role in the establishment of chronic pseudomonal lung infection in these patients. A third organism, Pseudomonas cepacia, has recently been detected in the airways of older patients with cystic fibrosis and is associated with increased mortality. The virulence of P. cepacia is not understood, but the organism is extremely refractory to antimicrobial therapy. Other bacteria, including Haemophilus influenzae and members of the family Enterobacteriaceae, appear to play a secondary role in airway infection. Aspergillus fumigatus is the most important fungal agent causing allergic bronchopulmonary disease. The role of viruses has only recently been examined. At least in some patients with cystic fibrosis, respiratory syncytial virus may be important in predisposing to subsequent bacterial infections.

Proteolytic inactivation of cytokines by Pseudomonas aeruginosa

Pseudomonas aeruginosa alkaline protease and elastase are thought to contribute to bacterial invasiveness, tissue damage, and immune suppression in animals and patients infected with the bacterium. This study examined the ability of the two proteases to inactivate a number of cytokines that mediate immune and inflammatory responses. Human recombinant gamma interferon (rIFN-gamma) and human recombinant tumor necrosis factor alpha were inactivated by both proteases. Murine rIFN-gamma was relatively resistant to alkaline protease but was inactivated by elastase, and human recombinant interleukin-1 alpha and recombinant interleukin-1 beta were resistant to the effects of both proteases. Western immunoblots suggested that cytokine inactivation by these proteases, where it occurred, required only limited proteolysis of the polypeptides. The ability of different P. aeruginosa strains to inactivate IFN-gamma appeared to require the production of both proteases for optimum activity. These results indicate that in vitro cytokine inactivation by Pseudomonas proteases is selective, requires only limited proteolysis, and in certain instances reflects the cooperative effects of both proteases.

Antibacterial therapy in cystic fibrosis

Bacterial lung infections determine the prognosis for most cystic fibrosis patients. The antibacterial therapy is difficult because of the host-bacterium interaction and altered pharmacokinetics. The new insights in the working mechanisms of antibiotics that may lead to better treatment results have been discussed, and guidelines for treatment of lung infections in cystic fibrosis patients were given.

Pseudomonas aeruginosa cross-colonization and persistence in patients with cystic fibrosis. Use of a DNA probe

To investigate cross-colonization with and persistence of Pseudomonas aeruginosa in cystic fibrosis (CF), 181 isolates from 76 CF patients were typed using a P. aeruginosa-specific DNA probe. Whereas sibling pairs predominantly harboured genotypically identical P. aeruginosa strains, all of the other patients harboured different strains. Seventy-nine per cent (22/31) of the infected CF patients harboured the same strains at the beginning and the end of a summer camp. A change of strains was seen in 10% (3/31) of the patients at the end of the camp. Forty-six per cent (6/13) of the patients who were apparently initially uninfected, acquired P. aeruginosa by the end of the period. Genotyping proved that strain change or acquisition was due to cross-colonization in four of nine cases. Very little P. aeruginosa was isolated from the inanimate environment. Persistence of P. aeruginosa after a temporary loss due to antibiotic therapy was seen in 12/16 paired patient strains before and after antibiotic therapy. Thus, suppression followed a flare-up seemed to occur in these patients rather than eradication and a new infection. When 35 patients were followed over a period of 6 months, 7 (20%) changed the strain in their sputum. Only one of 43 patients harboured two different P. aeruginosa strains simultaneously over a long period.

Effects of acute viral respiratory tract infections in patients with cystic fibrosis

To determine the effects of acute viral respiratory infections (ARI) in cystic fibrosis (CF) we studied all episodes of ARI in ten patients over a 2 year period. A daily diary card was kept on which they recorded all illnesses, including specific upper and lower respiratory symptoms, antibiotic use, and daily peak flow measurements. Recording of concurrent similar illnesses in other household members aided in confirming the onset of ARI, as did a home viral culturing technique and serial serum antibody levels against specific viral types. A total of 80% of the 35 recorded onsets of ARI (1.75/yr/subject) were confirmed by one or more of these methods. Five subjects with moderate to severe pulmonary function scores at the outset of the study had significantly greater decreases in PEFR during ARI episodes (42.4%) than those with milder disease (15.4%), and it took them significantly longer to recover to their baseline measurements (22 days vs. 15 days respectively). The majority of hospital admissions for pulmonary exacerbations were preceded by viral infections (7/8).

Treatment of Pseudomonas lung infection in cystic fibrosis with piperacillin plus tobramycin versus ceftazidime monotherapy: preliminary communication

Twenty-one patients with cystic fibrosis and chronic Pseudomonas lung infection were treated at random with ceftazidime, 150 mg/kg/day, or with piperacillin, 300 mg/kg/day, and tobramycin, 10 and more mg/kg/day for 14 days. On admission and at discharge, body weight, erythrocyte sedimentation rate, white blood cell count, and differential were determined. Pulmonary function analysis and chest X-rays were also obtained on both occasions as was sputum bacteriology. After hospitalization, the patients were followed in the outpatient department for 14-26 months. Both treatments were associated with significant improvement in most of the parameters that were studied, but neither treatment was superior.