Diagnosis of chronic Pseudomonas aeruginosa infection in cystic fibrosis by enzyme-linked immunosorbent assay

A portable SERS sensor for pyocyanin detection in simulated wound fluid and through swab sampling

A portable surface-enhanced Raman spectroscopy (SERS) sensor for detecting pyocyanin (PYO) in simulated wound fluid and from bacteria samples was developed. Solution-phase SERS detection protocols are designed to be compatible with two different clinical practices for wound exudate collection, namely negative pressure liquid collection and swabbing. For citrate-coated metal nanoparticles of three different compositions, i.e. gold (AuNPs), alloyed silver/gold (AgAuNPs), and silver (AgNPs), we firstly confirmed their interaction with PYO in the complex wound fluid, using fluorescence quenching experiments, which rationalized the Raman enhancement effects. We then demonstrated the Raman enhancement effects of the metal nanoparticles in the order of AgNPs > AgAuNPs > AuNPs. The limit of detection (LOD) achieved for PYO is 1.1 μM (in a linear range of 0.1-25 μM by the AgNPs), 10.9 μM (in a linear range of 5-100 μM, by the AgAuNPs), and 17.7 μM (in a linear range of 10-100 μM by the AuNPs). The AgNP and AgAuNP sensors together cover the sensitivity and dynamic range requirements for the clinical detection of wound infection, where PYO is present at a concentration of 1-50 μM. In addition, sterilized cotton swabs were used to collect wound fluid and transfer samples into AgNP solution for SERS measurements. This detection protocol was completed within 5 minutes with a LOD of 23.1 μM (in a linear range of 15-100 μM). The SERS sensing protocol was validated by its successful detection of PYO in cultured Pseudomonas aeruginosa bacteria. The findings presented in this work pave the way towards point-of-care diagnostics of wound infections.

KB001-A, a novel anti-inflammatory, found to be safe and well-tolerated in cystic fibrosis patients infected with Pseudomonas aeruginosa

BACKGROUND

Chronic Pseudomonas aeruginosa (Pa) airways infection, exuberant local inflammation, and progressive lung function loss are hallmarks of cystic fibrosis (CF). KB001-A is an anti-PcrV PEGylated monoclonal antibody fragment to the Type III secretion system of Pa. This 16-week study evaluated KB001-A associated effect on time-to-need for antibiotics for worsening respiratory signs and symptoms, as well as safety, and treatment-associated changes in symptom scores, inflammatory markers, and spirometry.

METHODS

This was a randomized, double-blind, placebo-controlled, repeat-dose study in CF subjects with Pa. Intravenous 10mg/kg KB001-A or placebo infusions were administered at baseline and weeks 2, 4, 8, and 16, with a 4-week follow-up. Sputum inflammatory markers were assessed in a sub-study. Time-to-need for antibiotics was compared between groups by Kaplan Meier analysis and Cox proportional hazards modeling adjusting for randomization strata.

RESULTS

Of 182 subjects, 169 received at least one infusion of KB001-A (n=83) or placebo (n=86). KB001-A was generally safe and well-tolerated as compared to placebo, with no significant emergent adverse effects other than one serious adverse event of elevated hepatic enzymes of unclear etiology. Time to need for antibiotics did not differ between groups (HR: 1.00; 95% CI: 0.69, 1.45, p=0.995). A 3.2 increase in ppFEV₁ from placebo favoring KB001-A was observed at week 16 (95% CI: 1.12, 5.30, p=0.003). Mean changes from baseline in log₁₀ sputum neutrophil elastase (NE) had a non-significant decrease (-0.27, 95% CI: -0.58,0.04, p=0.084) while IL-8 concentrations at week 16 were significantly lower (-0.27, 95% CI: -0.55,0.00, p=0.048) among KB001-A subjects (n=16) relative to placebo (n=13).

CONCLUSIONS

KB001-A was safe and well-tolerated and associated with a modest FEV₁ benefit and reduction in select sputum inflammatory markers (IL-8). KB001-A was not associated with an increased time to need for antibiotics. The lack of efficacy seen with KB001-A may be due, in part, to the low levels of the type III secretion proteins previously reported in sputum of CF patients chronically infected with Pa.

Anti-Pseudomonas aeruginosa IgG antibodies and chronic airway infection in bronchiectasis

BACKGROUND

Identification of chronic Pseudomonas aeruginosa (PA) infection is important in the management of bronchiectasis, but requires repeated sputum sampling. We hypothesized that serum anti-PA IgG antibodies could diagnose chronic PA infection at a single visit.

METHODS

Clinically stable bronchiectasis patients were studied prospectively. Chronic PA infection was defined as 2 or more positive sputum samples at least 3 months apart and/or failure to clear PA following eradication treatment. Baseline serum anti-PA IgG was determined by a validated ELISA kit.

RESULTS

A total of 408 patients were included. Sixty of them (14.7%) had chronic PA infection and had higher anti-PA IgG levels (median 6.2 vs. 1.3 units, p < 0.001). Antibody levels showed direct significant correlations with exacerbation frequency, the bronchiectasis severity index and sputum inflammatory markers. Fifty-seven patients with chronic PA infection had a positive test, giving 95% sensitivity, 74.4% specificity and AUROC of 0.87. During follow-up, 38 patients had a new PA isolation. Eradication at 12 months was achieved in 89.5% of subjects with a negative antibody test and 15.8% of patients with a positive test.

CONCLUSIONS

Anti-PA IgG test is highly accurate to detect chronic PA infection in bronchiectasis patients. In addition, it may be a marker of disease severity and treatment response.

Diagnostic and prognostic significance of systemic alkyl quinolones for P. aeruginosa in cystic fibrosis: A longitudinal study

Background

Pulmonary P. aeruginosa infection is associated with poor outcomes in cystic fibrosis (CF) and early diagnosis is challenging, particularly in those who are unable to expectorate sputum. Specific P. aeruginosa 2-alkyl-4-quinolones are detectable in the sputum, plasma and urine of adults with CF, suggesting that they have potential as biomarkers for P. aeruginosa infection.

Aim

To investigate systemic 2-alkyl-4-quinolones as potential biomarkers for pulmonary P. aeruginosa infection.

Methods

A multicentre observational study of 176 adults and 68 children with CF. Cross-sectionally, comparisons were made between current P. aeruginosa infection using six 2-alkyl-4-quinolones detected in sputum, plasma and urine against hospital microbiological culture results. All participants without P. aeruginosa infection at baseline were followed up for one year to determine if 2-alkyl-4-quinolones were early biomarkers of pulmonary P. aeruginosa infection.

Results

Cross-sectional analysis: the most promising biomarker with the greatest diagnostic accuracy was 2-heptyl-4-hydroxyquinoline (HHQ). In adults, areas under the ROC curves (95% confidence intervals) for HHQ analyses were 0.82 (0.75–0.89) in sputum, 0.76 (0.69–0.82) in plasma and 0.82 (0.77–0.88) in urine. In children, the corresponding values for HHQ analyses were 0.88 (0.77–0.99) in plasma and 0.83 (0.68–0.97) in urine.

Longitudinal analysis: Ten adults and six children had a new positive respiratory culture for P. aeruginosa in follow-up. A positive plasma HHQ test at baseline was significantly associated with a new positive culture for P. aeruginosa in both adults and children in follow-up (odds ratio (OR) = 6.67;-95% CI:-1.48–30.1;-p = 0.01 and OR = 70; 95% CI: 5–956;-p < 0.001 respectively).

Conclusions

AQs measured in sputum, plasma and urine may be used to diagnose current infection with P. aeruginosa in adults and children with CF. These preliminary data show that plasma HHQ may have potential as an early biomarker of pulmonary P. aeruginosa. Further studies are necessary to evaluate if HHQ could be used in clinical practice to aid early diagnosis of P. aeruginosa infection in the future.

Serology as a diagnostic tool for predicting initialPseudomonas aeruginosa acquisition in children with cystic fibrosis

RATIONALE

Pseudomonas aeruginosa (Pa) serology could potentially be a useful adjunct to respiratory culture methods for the detection of initial or early Pa infection in patients with cystic fibrosis (CF).

OBJECTIVE

To evaluate the utility of Pa serology to predict Pa isolation from respiratory (generally oropharyngeal) cultures in the subsequent 6 or 12 months among young children with CF from whom Pa had never been previously cultured. Pa serology was also evaluated in a group of healthy controls.

METHODS

Children ≤ 12 years of age without prior isolation of Pa from respiratory cultures participating in the Early Pseudomonal Infection Control EPIC Observational Study (EPIC OBS) had annual serum samples for measurement of antibodies against alkaline protease, elastase and exotoxin A using a commercial kit; controls had a single serum sample. Logistic regression with generalized estimating equations was used to characterize associations between log10 serum antibody titers and first isolation of Pa from a respiratory culture within the subsequent 6 or 12 months, with adjustment for sex and age. Receiver operating characteristic curves were used to optimize antibody titer cutpoints by age group. The diagnostic properties of each antibody were estimated using these optimized cutpoints.

RESULTS

Pa serology was evaluated in 582 children with CF (2084 serum samples) and 94 healthy controls. There was substantial overlap between serum antibody titers among controls, CF patients who did not acquire Pa (N = 261) and CF patients who did acquire Pa (N = 321). The maximum positive predictive value for first Pa positive culture within the ensuing 6 months was 76.2% and maximum negative predictive value was 72.1% for any antigen or combination of antigens; values were similar for 12 months.

CONCLUSIONS

Pa serology does not appear useful for predicting first Pa positive oropharyngeal culture among young CF patients.

Assessment of IgG antibodies to Pseudomonas aeruginosa in patients with cystic fibrosis by an enzyme-linked immunosorbent assay (ELISA)

Background

The usefulness of serological tests for detection of P. aeruginosa pulmonary infection in cystic fibrosis (CF) is controversial. Here, we assessed the value of detecting anti-P. aeruginosa IgG by a quantitative enzyme-linked immunosorbent assay (ELISA) for identification of P. aeruginosa infection in patients with cystic fibrosis.

Methods

Serum concentrations of anti-P. aeruginosa IgG were assessed in 117 CF patients classified according to their P. aeruginosa colonization/infection status (never colonized; free of infection; intermittently colonized and chronically infected) and in 53 healthy subjects by the ELISA test standardized with the St-Ag:1–17 antigen.

Results

The rate of IgG seropositivity and the median of IgG concentrations of this antibody in patients chronically infected were significantly higher than those found in the other CF groups and in the healthy control group.

Conclusion

Detection of anti-P. aeruginosa IgG can be an useful tool for identification of P. aeruginosa chronic infection in patients with CF.

Virtual Slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/13000_2014_158

Inflammatory and immunological biomarkers are not related to survival in adults with Cystic Fibrosis

BACKGROUND

Chronic Pseudomonas aeruginosa pulmonary infection is associated with a decline in lung function and reduced survival in people with Cystic Fibrosis (CF). Damaging inflammatory and immunological mediators released in the lungs can be used as markers of chronic infection, inflammation and lung tissue damage.

METHODS

Clinical samples were collected from CF patients and healthy controls. Serum IgG and IgA anti-Pseudomonas antibodies, sputum IL-8 and TNFα, plasma IL-6 and urine TNFr1 were measured by ELISA. Sputum neutrophil elastase (NE), cathepsin S and cathepsin B were measured by spectrophotometric and fluorogenic assays. The relationship between IgG and IgA, inflammatory mediators and long-term survival was determined.

RESULTS

IgG and IL-6 positively correlated with mortality. However, multivariate analysis demonstrated that after adjusting for FEV(1), IgG was not independently related to mortality. A relationship was observed between IgG and IL-6, TNFα, TNFr1 and between IgA and IL8, cathepsin S and cathepsin B.

CONCLUSIONS

These data indicate that biomarkers of inflammation are not independent predictors of survival in people with CF.

Reduced mortality in cystic fibrosis patients treated with tobramycin inhalation solution

BACKGROUND

Though tobramycin inhalation solution has been used for over a decade to improve lung function and reduce exacerbations in patients with cystic fibrosis (CF), its effects on mortality have not been well-described. This study aimed to assess the association between use of tobramycin inhaled solution and mortality in patients with CF and chronic Pseudomonas aeruginosa (PA) infection.

METHODS

Longitudinal logistic regression was used to assess the association between current-year reported use of tobramycin inhalation solution and subsequent-year mortality of patients meeting recommended criteria for tobramycin inhalation solution use in the United States Cystic Fibrosis Foundation's Patient Registry (1996-2008).

RESULTS

Among 12,740 patients meeting inclusion criteria, 2,538 deaths were observed during a median follow-up of 6 years. After regression adjustment, use of tobramycin inhaled solution was associated with a 21% reduction in the odds of subsequent year mortality (odds ratio (95% CI): 0.79 (0.72-0.88), P < 0.001). In our model, use of dornase alfa was also associated with a 15% reduction in the odds of subsequent year mortality (odds ratio (95% CI): 0.85 (0.76-0.95), P = 0.005). Underweight for age, CF-related diabetes, female gender, worse lung function and cultures positive for Pseudomonas aeruginosa or Burkholderia cepacia complex, among multiple other patient characteristics, were associated with significantly increased mortality. Adjusted mortality rates for patients reporting tobramycin inhalation solution use in all versus none of the follow-up years were 1.3% versus 2.1% at 2 years, 5.2% versus 8.0% at 5 years, and 9.9% versus 15.0% at 10 years.

CONCLUSION

After adjustment for multiple patient characteristics and known risk factors, use of tobramycin inhalation solution was associated with significantly reduced mortality among patients with CF.

Association between genotype and pulmonary phenotype in cystic fibrosis patients with severe mutations

BACKGROUND

Despite numerous studies a clear relationship between genotype and pulmonary phenotype has not been established within the group pancreatic insufficient cystic fibrosis (CF) patients. We studied the relationship between class I and class II mutations and pulmonary function in Swedish patients with known CFTR functional classification.

METHODS

170 CF patients with two class II mutations, 18 with two class I mutations and 78 with a combination of class I and II mutations were included in the study. Spirometry was performed when patients were in an optimal clinical condition.

RESULTS

Patients with two class I mutations had lower lung function (FEV(1) and FVC) compared to the group with either a combination of class I and II mutations or two class II mutations.

CONCLUSION

CF patients carrying two class I mutations risk developing more severe lung disease compared to patients with at least one class II mutation.

Gender differences in the Scandinavian cystic fibrosis population

AIMS

To explore whether gender differences in the Scandinavian Cystic Fibrosis (CF) patients exist in the areas of key clinical parameters, complications, and medication.

METHODS

Cross-sectional data on 890 (416 female) pancreatic insufficient CF patients were evaluated regarding chronic infection, body mass index, lung function, medication, and diabetes, as well as data of Pseudomonas infection status, antibiotic treatment and hospitalization from 1-year follow-up.

RESULTS

We found no differences in lung function, body mass index, or frequency of diabetes. The adult group consisted of more males than females (208:168). We found no significant difference in prevalence of chronic Pseudomonas aeruginosa infection, but during the follow-up the incidence of new chronic infection was higher in adult females (10/33 vs. 4/56). Females had higher prevalence of Burkholderia infection (21/416 vs. 11/474). Adult females had more days on intravenous antibiotics (median 39 vs. 26 days/year), and days in hospital (median 2 vs. 0 days/year). More adult females received inhaled and oral steroids. In the pediatric cohort, females were treated more often with macrolides as an anti-inflammatory agent.

CONCLUSION

We found no gender difference in key clinical parameters in our CF population. However, our study showed a higher risk of Pseudomonas and Burkholderia infection among the female patients. Additionally, we found that female patients require more intensified treatment regarding antibiotics, macrolides, steroids and days of hospitalization, indicating a true female disadvantage even with modern aggressive treatment. The finding of more males than females in the adult population suggesting a male advantage, warrants a mortality study.

Differences in prevalence and treatment of Pseudomonas aeruginosa in cystic fibrosis centres in Denmark, Norway and Sweden

BACKGROUND

Chronic Pseudomonas aeruginosa (PA) infection causes increased morbidity and mortality in cystic fibrosis (CF). This study aimed to answer the following questions: Does the prevalence of chronic infection with PA differ between the CF centres in Scandinavia? Which differences exist concerning segregation and treatment of PA?

METHODS

989 patients (86%) from all eight CF-centres in Scandinavia were included. Demographic and clinical data, including PA colonisation status based on cultures and serology, were recorded at inclusion. The patients were followed prospectively for 1 year, recording number of days with anti-PA antibiotic treatment.

RESULTS

In all pancreatic insufficient (PI) patients (n=890) the prevalence of chronic PA infection at each centre ranged from 25.8% to 48.9%, but were not significantly different. In PI patients <19 years the prevalence was 14.5% in Copenhagen compared to 30.9% in the Swedish centres pooled (p=0.001). In intermittently colonised PI patients <19 years the median number of days per year on anti-PA antibiotics was almost 6 times higher in Copenhagen (mean 86 (110), median 61 days) compared to the Swedish centres pooled (mean 27 (52), median 11 days) (p=0.037). The pulmonary function was similar.

CONCLUSIONS

It is possible to maintain a very low prevalence of chronic PA infection in CF patients <19 years. We speculate that this was most likely due to a very intensive treatment of intermittently colonised patients with inhaled anti-PA antibiotics over prolonged periods of time in some centres. Since lung function was similar in centres with less intensive use of inhaled antibiotics, studies comparing different treatment modalities and other parts of CF care are needed to define the best clinical practice, including how to use antibiotics in the most rational way.

Usefulness of serum IgG4 in the diagnosis and follow up of autoimmune pancreatitis: A systematic literature review and meta-analysis

High circulating serum immunoglobulin G4 (IgG4) levels have been proposed as a marker of autoimmune pancreatitis (AIP). The aim of the present study was to review the data existing in the English literature on the usefulness of the IgG4 serum levels in the diagnosis and follow up of patients with AIP. A total of 159 patients with AIP and 1099 controls were described in seven selected papers reporting the usefulness of serum IgG4 in diagnosing AIP. In total, 304 controls had pancreatic cancer, 96 had autoimmune diseases, and the remaining 699 had other conditions. The summary receiver-operating characteristic curve analysis was carried out by means of Meta-DiSc open-access software. Serum IgG4 showed good accuracy in distinguishing between AIP and the overall controls, pancreatic cancer and other autoimmune diseases (area under the curve [+/- SE]: 0.920 +/- 0.073, 0.914 +/- 0.191, and 0.949 +/- 0.024, respectively). The studies analyzed showed significantly heterogeneous specificity values in each of the three analyses performed. The analysis of the four studies comparing AIP and pancreatic cancers also showed significantly heterogeneous values of sensitivities and odds ratios. Regarding the usefulness of IgG4 as a marker of efficacy of steroid treatment, a decrease in the serum concentrations of IgG4 was found in the four available studies. The serum IgG4 subclass is a good marker of AIP, and its determination should be included in the diagnostic workup of this disease. However, the heterogeneity of the studies published until now means that more studies are necessary in order to better evaluate the true accuracy of IgG4 in discriminating AIP versus other autoimmune diseases.

More Than 10 Years' Continuous Oral Treatment with Specific Immunoglobulin Y for the Prevention ofPseudomonas aeruginosaInfections: A Case Report

Immunotherapy with specific antibodies is an alternative to antibiotics for the prevention of infections in humans and animals. We have used orally administered immunoglobulin Y (IgY) preparations, purified from eggs of hens immunized with Pseudomonas aeruginosa bacteria, to prevent pulmonary P. aeruginosa infections in a group of patients with cystic fibrosis (CF). Respiratory infections are major problems for CF patients because of the thick mucus in the airways, and chronic P. aeruginosa lung infections occur in virtually all CF patients and cause morbidity and mortality. The IgY-treated group had only 2.5 P. aeruginosa-positive sputum cultures per 100 months, and none of the IgY-treated patients became chronically colonized with P. aeruginosa. In the control group, 13.7 of the cultures per 100 months were positive for P. aeruginosa, and 24% of patients became chronically colonized with P. aeruginosa. The first enrolled patient in this study has now been treated continuously for more than 10 years. During the first 8 years she only had four P. aeruginosa-positive cultures. After 8 years she became chronically infected, but still after 10 years the bacteria have not turned mucoid. No negative side effects of IgY treatment have been noted during these 10 years. To our knowledge this is the longest treatment with specific yolk antibodies for therapeutic purposes.

Approaches to the Treatment of Initial Pseudomonas aeruginosa Infection in Children Who Have Cystic Fibrosis

Pseudomonas aeruginosa remains an important cause of pulmonary disease in patients who have cystic fibrosis. The development of antimicrobial therapy directed against this organism has resulted in the preservation of lung function and improved longevity. Efficacy has been demonstrated with agents administered via parenteral, inhaled, and oral routes. The optimal antibiotic regimen remains unclear. There is an active effort to use randomized, controlled clinical trials to rigorously test effective antibiotic for the eradication of P aeruginosa in young children or at least to delay the establishment of chronic infection.

Towards zero prevalence of chronic Pseudomonas aeruginosa infection in children with cystic fibrosis

BACKGROUND

Data from the Belgian Cystic Fibrosis Registry consistently show that in one of the seven reference centres, the prevalence of Pseudomonas aeruginosa is half that observed at the national level.

OBJECTIVES

To report the characteristics of non-transplanted patients in this clinic at the end of 2003, with special focus on paediatric patients. To describe and discuss our policy of inhaled antibiotic therapy.

FINDINGS

The prevalence of P. aeruginosa among 116 patients is 20.7%. The chronic colonization rate is 19.8% but only 2.8% in patients aged under 18 (n=72). Serologic data strongly support these results. Most paediatric patients (95%) are prescribed inhaled antibiotics, at least on an intermittent basis but the mean number of days of intravenous antibiotic treatment is four times lower than in other CF children in Belgium. 70% of children have an FEV1> or =90% predicted.

DISCUSSION

We have reported a distinctly low rate of chronic colonization by P. aeruginosa in a cohort of CF children and suspect that a strategy of early, often <<prophylactic>> use of inhaled antibiotics, progressively implemented for over 15 years has substantially contributed to these results. Given the major impact of chronic P. aeruginosa colonization on prognosis in CF, it is suggested that a large prospective study of this approach is warranted.

Diagnostic value of serological tests against Pseudomonas aeruginosa in a large cystic fibrosis population

BACKGROUND

Serological methods to monitor Pseudomonas aeruginosa colonisation in patients with cystic fibrosis (CF) are advocated but the diagnostic value of a commercially available P aeruginosa antibody test to detect early and chronic P aeruginosa colonisation in a non-research setting has not been assessed.

METHODS

Colonisation with P aeruginosa was estimated by regular culture of sputum or oropharyngeal swabs during three consecutive years in 220 patients with CF aged 0-65 years. Commercially available ELISA tests with three P aeruginosa antigens (elastase, exotoxin A, alkaline protease) were performed at the end of the study period. In a subgroup of 57 patients (aged 4-14 years) serological tests were performed annually.

RESULTS

Using culture as the reference standard, the ELISA tests using the advised cut off values had a sensitivity of 79% and a specificity of 89% for chronic colonisation. Receiver-operator characteristic curves were created to optimise cut off values. Applying these new cut off values resulted in a sensitivity of 96% and a specificity of 79%. All three individual serological tests discriminated well between the absence and presence of chronic P aeruginosa colonisation. The sensitivity of the individual antibody test was 87% for elastase, 79% for exotoxin A, and 76% for alkaline protease. First colonisation was preceded by positive serological results in only five of 13 patients (38%).

CONCLUSION

In patients with CF, serological tests using specific antigens are sensitive for diagnosing chronic P aeruginosa colonisation. However, the failure of serological tests to detect early colonisation in young patients emphasises the need for continued reliance on cultures.

Eradication of early Pseudomonas aeruginosa infection

Chronic pulmonary infection with Pseudomonas aeruginosa is responsible for most of the morbidity and mortality in cystic fibrosis (CF). Once established as a biofilm, chronic P. aeruginosa infection caused by the mucoid phenotype cannot be eradicated. However, a period of intermittent colonization with P. aeruginosa precedes the establishment of the chronic infection. This window of opportunity can be utilized to eradicate P. aeruginosa from the respiratory tract of CF patients by means of oral ciprofloxacin in combination with nebulized colistin for 3 weeks or, even better, for 3 months or by means of inhaled tobramycin as monotherapy for 4 weeks or longer. This early, aggressive eradication therapy has now been used for 15 years without giving rise to resistance to the antibiotics and without serious side effects. The therapeutic results have been very successful and have completely changed the epidemiology in the Danish Cystic Fibrosis Center and a few other centers which have used this strategy for several years. The chronic P. aeruginosa lung infection is not seen in CF infants and children anymore due to the aggressive therapy, and no other bacteria have replaced P. aeruginosa in these young patients. The aggressive therapy has been shown to very cost-effective, and a European Consensus report recommends this approach.

Detection of Pseudomonas aeruginosa in patients with cystic fibrosis

Chronic pulmonary colonisation with Pseudomonas aeruginosa (PA) in patients with CF is associated with a high morbidity and mortality. Adequate treatment of first acquisition of PA might prevent or postpone chronic colonisation. Early detection of PA is therefore of major importance. Currently, cultures of oropharynx or sputum are most commonly practised. However, oropharyngeal culture has limitations both in the positive and negative predictive value for the presence of PA in the lower respiratory tract. Induction of sputum has little benefit in detection of PA. Serology might have additional value in early detection, when bacterial density is too low to be detected by culture. Molecular techniques are not yet widespread used for detection of PA, but have in general a high sensitivity. In this review, we describe the value of different diagnostic techniques for detecting PA.

Insights into cystic fibrosis microbiology from the European tobramycin trial in cystic fibrosis

The infection of the airways of cystic fibrosis patients by Pseudomonas aeruginosa is a complex, multistaged process that is associated with a deterioration of lung function. The complexity of the formation of biofilms and their interaction with the immune system means that treatment with antibiotics has been an uncertain science. Tobramycin nebuliser solution (TNS) is a novel formulation of the antibiotic tobramycin developed specifically for inhalation. A recent large trial comparing TNS with inhaled colistin provided an opportunity to define further the effect of antibiotic treatment on microbial infection. In the TNS group, the percentage of patients with a tobramycin minimal inhibitory concentration (MIC) > or = 4 mg l(-1) increased from 38 to 49%, and the percentage of patients with a colistin MIC > or = 4 mg l(-1) remained at 55%. In the colistin group, the percentage of patients with a colistin MIC > or = 4 mg l(-1) remained at 34%, whereas the percentage of patients with a tobramycin MIC > or = 4 mg l(-1) decreased from 27 to 16%. Furthermore, clinical and bacterial response to TNS and colistin was independent of the MIC at baseline. Neither antimicrobial therapy was associated with infection by Burkholderia cepacia or other inherently resistant pathogens. We conclude that conventional measures of antimicrobial resistance may underestimate the effectiveness of tobramycin and colistin when delivered at the high concentrations achieved with the TNS formulation.

Oral administration of specific yolk antibodies (IgY) may prevent Pseudomonas aeruginosa infections in patients with cystic fibrosis: a phase I feasibility study

Respiratory infection is the major cause of morbidity and mortality in cystic fibrosis (CF) patients. Chronic Pseudomonas aeruginosa (PA) infections ultimately occur in virtually all patients. It is impossible to eradicate PA when a patient has been chronically colonized. Immunotherapy with specific egg-yolk antibodies (IgY) may be an alternative to antibiotics for the prevention of PA infections. We wanted to determine if treatment with specific IgY can prolong the period between the first and the second PA colonization? And long-term, can the treatment diminish the number of positive PA cultures and postpone the onset of chronic colonization? CF patients gargled daily with an IgY-antibody preparation, purified from eggs of hens immunized with PA bacteria. They were compared to a group of patients who did not gargle with the preparation. Both groups had their first colonization with PA eradicated by antibiotics. The basic treatment was essentially the same in both groups. In the initial study, the period between the first and second colonization with PA was significantly prolonged for the treated vs. the control group (Kaplan-Meier P = 0.015, Breslow test). In the prolonged study, the treated group had only 2.5 sputum cultures positive for PA per 100 months of observation, and none of these patients became chronically colonized with PA. No adverse events were reported. In the control group, 13.7 cultures per 100 months of observation were positive for PA, and 5 (24%) patients became chronically colonized with PA. This feasibility study shows that antipseudomonal IgY has the potential to effectively prevent PA colonization without any severe adverse effects. A phase III study should be initiated.

Anti-Pseudomonas aeruginosa antibody detection in patients with bronchiectasis without cystic fibrosis

BACKGROUND

Pseudomonas aeruginosa is a frequent cause of infection in patients with bronchiectasis. Differentiation between non-infected patients and those with different degrees of P aeruginosainfection could influence the management and prognosis of these patients. The diagnostic usefulness of serum IgG antibodies againstP aeruginosa outer membrane proteins was determined in patients with bronchiectasis without cystic fibrosis.

METHODS

Fifty six patients were classified according to sputum culture into three groups: group A (n=18) with no P aeruginosain any sample; group B (n=18) with P aeruginosa alternating with other microorganisms; and group C (n=20) with P aeruginosa in all sputum samples. Each patient had at least three sputum cultures in the 6 months prior to serum collection. Detection of antibodies was performed by Western blot and their presence against 20 protein bands (10–121 kd) was assessed.

RESULTS

Antibodies to more than four bands in total or to five individual bands (36, 26, 22, 20 or 18 kd) differentiated group B from group A, while antibodies to a total of more than eight bands or to 10 individual bands (104, 69, 63, 56, 50, 44, 30, 25, 22, 13 kd) differentiated group C from group B. When discordant results between the total number of bands and the frequency of P aeruginosa isolation were obtained, the follow up of patients suggested that the former, in most cases, predicted chronic P aeruginosacolonisation.

CONCLUSION

In patients with bronchiectasis the degree of P aeruginosa infection can be determined by the number and type of outer membrane protein bands indicating which serum antibodies are present.

Anti-Pseudomonas aeruginosa antibody detection in patients with bronchiectasis without cystic fibrosis

BACKGROUND

Pseudomonas aeruginosa is a frequent cause of infection in patients with bronchiectasis. Differentiation between non-infected patients and those with different degrees of P aeruginosa infection could influence the management and prognosis of these patients. The diagnostic usefulness of serum IgG antibodies against P aeruginosa outer membrane proteins was determined in patients with bronchiectasis without cystic fibrosis.

METHODS

Fifty six patients were classified according to sputum culture into three groups: group A (n=18) with no P aeruginosa in any sample; group B (n=18) with P aeruginosa alternating with other microorganisms; and group C (n=20) with P aeruginosa in all sputum samples. Each patient had at least three sputum cultures in the 6 months prior to serum collection. Detection of antibodies was performed by Western blot and their presence against 20 protein bands (10-121 kd) was assessed.

RESULTS

Antibodies to more than four bands in total or to five individual bands (36, 26, 22, 20 or 18 kd) differentiated group B from group A, while antibodies to a total of more than eight bands or to 10 individual bands (104, 69, 63, 56, 50, 44, 30, 25, 22, 13 kd) differentiated group C from group B. When discordant results between the total number of bands and the frequency of P aeruginosa isolation were obtained, the follow up of patients suggested that the former, in most cases, predicted chronic P aeruginosa colonisation.

CONCLUSION

In patients with bronchiectasis the degree of P aeruginosa infection can be determined by the number and type of outer membrane protein bands indicating which serum antibodies are present.

Specific IgG subclass antibody pattern to Aspergillus fumigatus in patients with cystic fibrosis with allergic bronchopulmonary aspergillosis (ABPA)

BACKGROUND

IgG and IgG subclass antibodies to Aspergillus fumigatus (A fumigatus) were measured in a large population of patients with cystic fibrosis to elucidate a putative antibody pattern specific for allergic bronchopulmonary aspergillosis (ABPA).

METHODS

An ELISA technique using water soluble somatic hyphal (WSSH) A fumigatus antigens and subclass specific monoclonal antibodies was used for cross sectional quantification of IgG and IgG1-4 subclass antibody levels in the serum of 238 patients with cystic fibrosis and 107 healthy controls.

RESULTS

In patients with cystic fibrosis persistently colonised with A fumigatus the subclass antibody levels were significantly increased compared with patients with cystic fibrosis never or rarely colonised (p < 0.001). The group of patients persistently colonised with A fumigatus with ABPA (+Af+ABPA) had significantly increased levels of IgG antibodies to A fumigatus (Af-IgG) (median 69 ELISA units (EU) versus 31) and of subclasses Af-IgG1 (91 versus 27), Af-IgG2 (143 versus 56), and Af-IgG4 antibodies (72 versus 20), but not of IgG3 (17 versus 15), compared with the colonised patients without ABPA (+Af-ABPA). Patients with cystic fibrosis with no or only rare isolates of A fumigatus without ABPA (-Af-ABPA) also had significantly increased subclass antibody levels (Af-IgG1 9 versus 3, Af-IgG2 28 versus 5, Af-IgG4 16 versus 4; p < 0.001) compared with healthy controls. Low, although detectable, levels of antibodies were demonstrated in healthy controls. ABPA seemed to occur independently of Pseudomonas aeruginosa infection. Using diagnostic cut off levels for ABPA, sensitivity and specificity were calculated. The highest specificity was found for IgG4 (88%); sensitivity was between 65% and 73%. The positive predictive values (PPV) were moderate, whereas the negative predictive values (NPV) were high (96% in all subclasses except IgG3 with 94%). PPV increased to 50% if IgG1 as well as IgG2 and IgG4 were included.

CONCLUSIONS

In a large number of unselected patients with cystic fibrosis significantly increased levels of Af-specific antibodies belonging to total IgG and all four subclasses were found in all groups of patients compared with healthy controls. In patients persistently colonised with A fumigatus these levels were significantly higher than in non-colonised patients, and the significantly highest levels (with the exception of IgG3) were found in patients with ABPA. Using a sensitive ELISA technique, measurements of IgG and IgG subclass antibodies to A fumigatus might be of importance in the management of ABPA, especially as a screening test to exclude the presence of ABPA; other tests are needed to confirm the diagnosis.

Controlled trial of inhaled budesonide in patients with cystic fibrosis and chronic bronchopulmonary Psuedomonas aeruginosa infection

The efficacy and safety of anti-inflammatory treatment with inhaled glucocorticosteroids in patients with cystic fibrosis (CF) and complicating chronic Pseudomonas aeruginosa (P.a.) lung infection was studied in a placebo-controlled, parallel, double-blind single center trial. Active treatment consisted of budesonide dry powder, 800 microg twice daily, delivered from a Turbuhaler. The study period covered two successive 3-mo intervals between elective courses of intravenous anti-Pseudomonas antibiotics. Fifty-five patients entered the study, with a mean age of 20 yr and a mean FEV1 of 63% of predicted. Analysis of all patients entered, irrespective of trial adherence ("intention to treat"), showed a decrease in FEV1 in the first period of -0.032 L in patients on budesonide versus -0.187 L in patients on placebo (p = 0.08). The corresponding figures for the patients adhering to the protocol during the first period were -0.017 L versus -0.198 L (p < 0.05, confidence interval of the difference: -0.035 to +0.327 L). For all patients entered, as well as for patients adhering to the trial, there was always a trend in favor of budesonide, as judged by changes in FEV1 and FVC in both 3-mo periods. None of the patients had asthma, but the patients on budesonide had a mean improvement in histamine reactivity of +1.15 dose steps over the entire 6-mo period, as opposed to +0.017 dose steps in patients on placebo (p < 0.05). There was also a significant (p = 0.01) correlation between pre-trial histamine reactivity and the change in FEV1 in the first period in patients on budesonide. We conclude that inhaled glucocorticosteroids can be of short-term benefit in patients with CF and chronic P.a. infection and that those patients most likely to benefit from this treatment are patients with hyperreactive airways. Prolonged studies in larger number of patients are necessary to determine the long-term efficacy of this treatment.

Quantitative analysis of the IgG and IgG subclass immune responses to chromosomal Pseudomonas aeruginosa beta-lactamase in serum from patients with cystic fibrosis by western blotting and laser scanning densitometry

BACKGROUND

Antibodies against chromosomal beta-lactamase of Pseudomonas aeruginosa (a beta ab) are markers of the development of resistance of P aeruginosa to beta-lactam antibiotics in patients with cystic fibrosis and chronic lung infection. The role of these antibodies in patients with chronic lung infection with P aeruginosa was further investigated by correlating the a beta ab IgG subclasses with pulmonary function in patients with cystic fibrosis.

METHODS

Immunoglobulin G (IgG) and IgG subclass a beta ab were investigated by western blotting and quantified by laser scanning densitometry. A longitudinal study on 43 consecutive patients with cystic fibrosis who developed chronic lung infection with P aeruginosa was performed.

RESULTS

IgG subclass a beta ab appeared in all patients with chronic infection with P aeruginosa. Eleven years after the onset of infection all the patients had IgG1, 79% had IgG4, 56% IgG2, and only 16% of the patients had IgG3 a beta ab. The IgG1 and IgG4 a beta ab appeared first, and more than 50% of the patients were IgG1 and IgG4 a beta ab positive within 2-3 years of the onset of infection, but IgG2 positivity only appeared after seven years and IgG3 remained absent from most of the patients. The median a beta ab levels increased during chronic infection: 100-fold for IgG1, 22-fold for IgG2, and 45-fold for IgG4. A 16-fold increase in the IgG3 a beta ab levels was detected in the six patients who developed IgG3 a beta ab. In the first four years of the chronic infection the a beta ab titres were higher in patients with good lung function than in those with poor lung function.

CONCLUSIONS

The association of a weak IgG3 and a strong IgG4 a beta ab response suggests that the contribution of a beta ab antibodies to lung diseases mediated by immune complexes might be less important than other antipseudomonal antibodies. A beneficial neutralising effect of the a beta ab antibodies on the antibiotic destroying enzymes may be an additional factor.

Precipitating Pseudomonas aeruginosa antibodies and antimicrobial therapy in cystic fibrosis patients

Forty patients with cystic fibrosis were studied bacteriologically and serologically. Precipitating Pseudomonas aeruginosa antibodies were monitored by crossed-immunoelectrophoresis (CIE) in order to evaluate the possibility of preventing chronic colonization by Pseudomonas aeruginosa by cycles of antimicrobial therapy. Sputum or pharyngeal aspirate and serum samples from all patients were analyzed by means of spread on selective media and CIE, respectively. Significant differences in the number of precipitins were obtained: noncolonized and intermittently colonized patients had no precipitins, whereas the number of precipitins in the chronically colonized patients varied from 11 to 44. An increase in the number of precipitins could be a good marker for initiation of therapy with antimicrobial agents that are either active against Pseudomonas aeruginosa or able to inhibit the release of virulence factors.

Specific decrease of anti-pseudomonal IgA after anti-pseudomonal therapy in cystic fibrosis

In patients with cystic fibrosis (CF) and chronic colonisation with Pseudomonas aeruginosa, specific anti-pseudomonal IgG and IgA, as well as serum immunoreactive protein C, WBC and differential count, ESR, pulmonary function and chest radiograph score were determined before and after a 2 week intravenous course of anti-pseudomonal antibiotics in 32 cases of acute exacerbation of pulmonary infection. Specific anti-pseudomonal IgA but not specific anti-pseudomonal IgG decreased significantly after treatment. Log of anti-pseudomonal IgA but not log anti-pseudomonal IgG correlated well with disease severity as assessed by the Brasfield chest radiograph score (r 0.57), forced expiratory volume in 1 s (r 0.6) as well as C-reactive protein (r 0.62).

CONCLUSION

Specific anti-pseudomonal IgA may be a better parameter than specific IgG in the follow up of lung infection in patients with CF, probably because it more closely reflects ongoing endobronchial infection, the major pathology in CF lungs.

Pseudomonas aeruginosa cytotoxin as a pathogenicity factor in a systemic infection of leukopenic mice

The effect of Pseudomonas aeruginosa cytotoxin was assessed in leukopenic outbred Swiss male mice (20 g) using a high cytotoxin-producing strain (PA158) and its cytotoxin-deficient isogenic mutant (PA114F5) generated by Tn7::Tn5 transposon mutagenesis of PA158. Leukopenia was induced by intraperitoneal (i.p.) administration of cyclophosphamide (150 micrograms/g). Anesthetized mice were infected via a 4 mm incision on the shaved back with 300 CFU/mouse (9 LD50; expected death rate 85%). Precleared mouse cytotoxin-specific heat inactivated rabbit polyclonal antibody (RPA) was administered i.p. (0.2 ml) 24 hr before challenge. Controls received i.p. normal rabbit serum, RPA, cyclophosphamide alone, or a sham procedure. Challenge with the high cytotoxin-producing strain PA158 caused earlier and a significantly greater mortality than that observed with a cytotoxin-deficient strain PA114F5 (P < 0.01). Cytotoxin-specific polyclonal antibody was protective. Pretreatment with antibody decreased the mortality rate following challenge with PA158 from 88.9% to 27.8% (P < 0.01). Pretreatment with antibody decreased the mortality rate following challenge with PA114F5 from 27.8% to 5.6% (P < 0.05). These results demonstrate that P. aeruginosa cytotoxin contributes to the pathogenicity of the organism and that cytotoxin antibody is protective in a systemic P. aeruginosa infection in leukopenic mice.

Immunoglobulin G antibodies to Pseudomonas aeruginosa lipopolysaccharides and exotoxin A in patients with cystic fibrosis or bacteremia

IgG antibodies to nine Pseudomonas aeruginosa lipopolysaccharides (LPS) and exotoxin A in sera from 11 patients with bacteremia and 51 patients with cystic fibrosis (CF) were analyzed. The methods used were enzyme immunoassay (EIA) and immunoblotting. Nine of the 11 bacteremic patients were infected with strains expressing an LPS serotype identical to one of the test antigens. In sera from six of these nine patients, antibody homologous to the serotype of the infecting strain was observed. An antibody response to heterologous Pseudomonas aeruginosa LPS antigens was observed in nine patients. Eight of the bacteremic patients mounted an antibody response to exotoxin A. Thirty-five CF patients chronically colonized with Pseudomonas aeruginosa possessed significantly higher levels of antibody to all of the test antigens than 16 patients with intermittent or no colonization (p < 0.001). For exotoxin A and serotype 3 the sensitivity was 91% and 94%, and the specificity 94% and 88% respectively. When the results for exotoxin A and serotype 3 were combined, the sensitivity was 91% while the specificity was 81%. The pronounced antibody response to heterologous LPS antigens, as measured by the EIA and immunoblot, suggests expression of a common antigen determinant. A simplified serological assay utilizing exotoxin A and serotype 3 as test antigens may be useful for detecting Pseudomonas aeruginosa infections in patients with CF and chronic colonization and in bacteremic patients from whom cultures are not available.

Microbiology of cystic fibrosis lung infections: themes and issues

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Antibody responses to lipid A, core, and O sugars of the Pseudomonas aeruginosa lipopolysaccharide in chronically infected cystic fibrosis patients

Enzyme-linked immunosorbent assays were developed separately for the three main parts of the Pseudomonas aeruginosa lipopolysaccharide (LPS) molecule, namely, lipid A, core, and O polysaccharide. Anti-lipid A, anticore, and anti-O polysaccharide antibodies were measured in serum samples from 12 patients with cystic fibrosis (CF) in a longitudinal study covering the period before P. aeruginosa infection was established through at least 5 years of chronic infection. The serum antibody response to all parts of the P. aeruginosa LPS molecule increased during the course of chronic infection. The increase in anti-lipid A antibodies was specific for P. aeruginosa lipid A, since no increase in anti-Escherichia coli lipid A antibodies was seen. Immunoglobulin G, A, and M (IgG, IgA and IgM) antibodies were all involved in the specific systemic response to P. aeruginosa lipid A, core, and the O polysaccharides. IgG and IgA levels in particular increased during the course of infection and were significantly higher than the antibody increase seen with age in a healthy control group. The local immune response in the lungs was investigated by measuring IgG, IgA, and IgM antibodies to the separate parts of the P. aeruginosa LPS molecule in sputum samples from 18 CF patients with at least a 5-year history of chronic P. aeruginosa infection. Antibodies detected in sputum were mainly anti-lipid A and anti-O polysaccharide antibodies of the IgG and IgA isotypes. Very high IgA anti-lipid A titers were detected in sputum samples from some CF patients.

Role of alginate in infection with mucoid Pseudomonas aeruginosa in cystic fibrosis

BACKGROUND

Chronic bronchopulmonary infection with mucoid, alginate producing Pseudomonas aeruginosa occurs characteristically in patients with cystic fibrosis. Alginate may be a virulence factor for P aeruginosa infection in such patients.

METHODS

Forced vital capacity (FVC), nutritional state and the antibody response to P aeruginosa were determined at regular intervals from three years before chronic P aeruginosa infection to 10 years afterwards in 73 patients with cystic fibrosis. All patients were treated intensively with antipseudomonal chemotherapy during the study period.

RESULTS

FVC was reduced in all patients who subsequently developed P aeruginosa infection before they acquired the infection, indicating significant pre-existing lung damage when compared with patients who remained free of P aeruginosa. Lung function and nutritional state remained unchanged after 10 years of infection, except in the patients who died of P aeruginosa lung infection. The FVC and height and weight of patients infected with nonmucoid strains of P aeruginosa were similar to those of uninfected patients. Patients infected with mucoid strains had poorer lung function and nutritional state for the first five years after infection compared with patients with nonmucoid strains. Such infection was also associated with greater IgG and IgA antibody responses to P aeruginosa standard antigen compared with nonmucoid infection. Concentrations of antibody to alginate were similar in patients with non-mucoid and mucoid infection. Noticeably increased concentrations of IgA antibodies to P aeruginosa standard antigen were observed early after the onset of infection in patients who subsequently died.

CONCLUSION

Alginate producing P aeruginosa infection is associated with a hyperimmune response and poor clinical condition, suggesting that alginate production is a virulence factor in such infections in patients with cystic fibrosis.

Cloning and sequencing of the genes coding for the 10- and 60-kDa heat shock proteins from Pseudomonas aeruginosa and mapping of a species-specific epitope

A genomic library of Pseudomonas aeruginosa DNA was screened with a monoclonal antibody (MAb 2528) specific for the P. aeruginosa 60-kDa heat shock protein. A positive clone, pAS-1, was isolated. The gene coding for P. aeruginosa chaperonin (hsp60) was localized to a 2-kb EcoRI fragment subcloned in pAS-2. A sequence analysis of pAS-2 and parts of pAS-1 identified two open reading frames that encoded proteins with calculated molecular masses of 10 and 57 kDa. In amino acid sequence comparison studies the sequences of these proteins, which were designated GroES and GroEL, exhibited up to 78% homology with known prokaryotic sequences of 10- and 60-kDa heat shock proteins (hsp10 and hsp60). In order to map the epitope recognized by MAb 2528, a series of GroEL nested carboxy-terminal deletion clones were tested with MAb 2528. We identified the clone with the shortest insertion that was still recognized by MAb 2528 and the clone with the largest insertion that was not recognized by MAb 2528. The 3' ends of the insertions were determined by sequencing and were found to delimit a region that encoded 25 amino acid residues. Synthetic oligonucleotides that coded for peptides possibly resembling the epitope within this region were ligated into expression vector pGEX-3X, and fusion proteins expressed by these clones were tested for reactivity with MAb 2528. By using this method we determined that the decapeptide QADIEARVLQ (positions 339 to 348 on GroEL) was responsible for the binding of P. aeruginosa-specific MAb 2528.

IgG subclass antibodies to Pseudomonas aeruginosa in sera from patients with chronic Ps. aeruginosa infection investigated by ELISA

ELISAs using subclass-specific monoclonal antibodies were developed for the quantification of human IgG1, IgG2, IgG3 and IgG4 antibodies to Ps. aeruginosa. We investigated the pattern of IgG subclass antibodies against Ps. aeruginosa in serum from patients with cystic fibrosis (CF), other patients with chronic Ps. aeruginosa infection, and healthy controls. Healthy controls and patients with CF but without Ps. aeruginosa infection showed no or very low titres of antibodies against Ps. aeruginosa. In the early stage of chronic Ps. aeruginosa infection, antibody titres in all four subclasses were significantly higher than either normals or CF patients without infection. Other patients with Ps. aeruginosa infection showed the same increased level of IgG subclass antibodies as CF patients in an early stage of infection. Sixteen patients (eight in good and eight in poor clinical condition) have been followed for an average of 13 years with multiple serum samples covering the pre-infection, early and late stages of chronic infection. Patients in a poor clinical condition showed significantly higher levels of IgG3 antibodies in the first year of infection and 2 years later also had significantly higher IgG2 antibody levels. We conclude that elevated levels of IgG2 and IgG3 antibodies to Ps. aeruginosa are a sign of poor prognosis in CF.

Protection against mucoid Pseudomonas aeruginosa in rodent models of endobronchial infections

Chronic endobronchial infection with mucoid Pseudomonas aeruginosa accounts for much of the morbidity and mortality in patients with cystic fibrosis (CF). Reduced morbidity is observed when infection is absent. Clinical investigations have implicated opsonizing antibody specific for the mucoid exopolysaccharide (MEP) surrounding these bacteria as a potential immunologic protective mechanism, whereas nonopsonizing antibody to MEP is not protective. Mice and rats immunized with doses of MEP that elicited opsonizing antibody had reduced levels of infection compared with nonimmune controls after intratracheal challenge with mucoid P. aeruginosa enmeshed in agar beads. Doses of MEP that elicited nonopsonizing antibody were not protective. Parallel experiments in which passive transfer of polyclonal and monoclonal opsonizing and nonopsonizing antibody were used yielded similar results. These data indicate that MEP-specific opsonizing antibody can protect against chronic P. aeruginosa infection in this model of disease.

Antibody response of fibrocystic patients to homologous 0-typable and 0-defective isolates of Pseudomonas aeruginosa

Antibody titres to Pseudomonas aeruginosa of sera from 60 adult fibrocystic patients were determined in an enzyme linked immunosorbent assay (ELISA) with whole cells of homologous isolates which had been classified according to 0-antigen state by their reactivity with 0-typing antisera. Patients who were continuously colonised with Ps aeruginosa gave the highest titres: range 1500-64000 (mean 11000) and 500-48000 (mean 9000) with homologous 0-typable and 0-defective isolates, respectively. Lower titres to both varieties of isolates were obtained with recently colonised patients, and non-colonised patients gave titres with reference laboratory strains marginally above those of healthy controls. Serum titres of patients with sequential isolates were strain dependent and did not correlate with the 0-antigen state of the strain. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblot analysis of these sera and strains showed antibody binding primarily to high molecular weight 0-repeating units of lipopolysaccharide. It is concluded that the 0-antigen of the strain of Ps aeruginosa used in the ELISA test does not influence the titre obtained with fibrocystic sera, and it is recommended that serum titres should be assessed with a panel of homologous isolates from patients.

Immunoglobulin A and immunoglobulin G antibody responses to alginates from Pseudomonas aeruginosa in patients with cystic fibrosis

Patients with cystic fibrosis have a high prevalence of mucoid, alginate-producing Pseudomonas aeruginosa that causes chronic infection of the mucosal surface of the lungs. We developed enzyme-linked immunosorbent assays (ELISAs) for determination in serum of immunoglobulin A (IgA) and IgG antibodies to alginate purified from P. aeruginosa and an ELISA for detection of IgA antibodies to a polyvalent P. aeruginosa standard antigen. Absorption experiments indicated that the assays were antigen and antibody specific and had analytical variations that ranged from 7 to 19%. Serum samples from 207 patients with cystic fibrosis, 100 healthy children, and 94 healthy adults were examined. The patients responded to P. aeruginosa infection with early IgA and IgG antibody responses that were significantly higher than in controls and noncolonized patients. Analysis of paired serum samples showed that infected patients had an increase in specific IgG and IgA antibodies that was significantly higher than in noncolonized patients. The serological data were analyzed for correlation with clinical condition; poor lung function was significantly associated with increased levels of IgA and IgG antibodies to P. aeruginosa alginate and to the standard antigen and with a relative excess of IgA antibodies to the standard antigen compared with IgA antibodies to P. aeruginosa alginate. The assays showed high predictive values if positive, but a negative test did not exclude infection, and the ELISAs should not be used for diagnostic purposes. Mucoid strains were present initially in the sputa of 28 of 54 infected patients with paired serum samples. These patients had a significant increase in anti-alginate antibodies, but it was not different from the increase seen in patients infected only with nonmucoid strains. Therefore, alginate may also be produced in vivo by nonmucoid P. aeruginosa. The study showed that early formation of IgA and IgG antibodies to P. aeruginosa alginate did not prevent development of chronic infection and that P. aeruginosa-specific IgA antibodies correlate with poor lung function.

Serum IgA antibodies against Pseudomonas aeruginosa in cystic fibrosis

Serum IgA antibodies to Pseudomonas aeruginosa cell surface antigens were estimated by ELISA. Titres in patients with and without cystic fibrosis and with no pseudomonal infection were low (less than 105 to less than 261). Titres in patients with cystic fibrosis who were chronically infected with P aeruginosa were very high (1200-163,000), and patients who grew the organism intermittently had intermediate titres. Longitudinal studies suggested increasing tissue invasion or involvement of the lower respiratory tract, or both, with increasing time of infection and identified patients with a good prognosis after the onset of pseudomonal infection. Detection of an increased serum IgA titre can give an earlier indication than measurement of the serum IgG titre of the presence of P aeruginosa in the respiratory tract in a proportion of patients. IgA measurement seems to be better than IgG measurement at predicting the reappearance of P aeruginosa after apparent eradication of early infection. These results suggest that this assay may be a valuable additional indicator of the presence of P aeruginosa at the beginning of infection, and of the reappearance of the organism after treatment in the early stages of infection.

Pseudomonas aeruginosa flagellar antibodies in patients with cystic fibrosis

An enzyme-linked immunosorbent assay specific for flagellum type (a or b) of Pseudomonas aeruginosa was used to detect serum immunoglobulin antibodies in 98 random outpatients and 14 colonized cystic fibrosis patients. Antibodies were detected to both types of flagella in addition to M-2 lipopolysaccharide. Titers to both flagellar antigens (FlAg) were 10 to 100 times higher in cystic fibrosis patients than in random outpatients of a comparable age group. Mean antibody titers against b-type FlAg were 454 for outpatients (ages newborn to 21 years), whereas the mean titer for cystic fibrosis patients (ages 6 to 21 years) was 51,520. Titers against a-type FlAg were generally lower, with mean outpatient titers of 68 and mean cystic fibrosis patient titers of 34,323. Differences were also seen in antibody titer against M-2 lipopolysaccharide, but these differences did not correspond to M-2 FlAg titers. In 98 random outpatients (ages newborn to 86 years), FlAg titers generally increased with age. To demonstrate further specificity of the enzyme-linked immunosorbent assay for flagellum antibody, Western blots were performed with selected high-titer cystic fibrosis patient sera. Sera that had a high titer (greater than 25,600) for b- or a-type FlAg showed a corresponding reactive band. These results demonstrate that flagellum antibodies are produced in humans in response to P. aeruginosa infection.

Pseudomonas aeruginosa antibodies in blood spots from patients with cystic fibrosis

The formation of antibodies to Pseudomonas aeruginosa may be the earliest indicator of pulmonary infection in patients with cystic fibrosis. To enable easy sampling in babies and young children an enzyme linked immunosorbent assay (ELISA) based on a blood spot sample taken on to blotting paper was developed. A sample of approximately 20 microliters of blood was required. A high correlation and level of absolute agreement was shown between paired finger prick and venepuncture blood spots, and between blood spot, serum spot, and serum samples. Healthy controls and non-infected patients with cystic fibrosis had low titres of antibody compared with patients with intermittent and chronic infection. The latter groups had significantly greater antibody titres than normal controls. This assay permits serial measurement of antibodies to P aeruginosa in patients of all ages with cystic fibrosis and may provide a means of assessing the value of such measurements in the detection and management of early infection.

Antilipopolysaccharide antibodies and differential diagnosis of chronic Pseudomonas aeruginosa lung infection in cystic fibrosis

Chronic lung infection in cystic fibrosis is characteristically associated with polyagglutinable, serum-sensitive, mucoid strains of Pseudomonas aeruginosa. Enzyme-linked immunosorbent assay (ELISA) methods for standard-free quantitation of immunoglobulin G (IgG) and IgM antibodies to P. aeruginosa lipopolysaccharides (LPSs) have been developed. We now report the development of assays for quantitation of monomer and dimer total IgA and IgA anti-LPS antibodies. Use of these methods in diagnosis of early chronic P. aeruginosa lung infection was assessed. IgG and IgA anti-LPS levels increased significantly at the onset of chronic infection and continued to increase to very high levels in the later stages of infection. IgM anti-LPS levels also rose at the onset of chronic infection but did not increase further. The function of true- and false-positive rates was illustrated by using various concentrations of IgG, IgA, and IgM anti-LPS for discrimination of patients. Values that gave optimum separations were used for statistical evaluation of the diagnostic sensitivities and specificities of anti-LPS antibody concentrations. The results obtained in these assays were compared with a diagnosis, based on the number of precipitins in crossed immunoelectrophoresis, of serum samples from cystic fibrosis patients. In 64 paired serum samples taken before and immediately after the onset of chronic infection, as defined by crossed immunoelectrophoresis precipitins, the predictive values of a positive ELISA were 86% for IgG and 89% for IgA. The predictive values for a negative ELISA were 98% for IgG and 97% for IgA. Results of the IgM anti-LPS ELISA had a lower predictive value. Immunoblotting and absorption studies showed that IgG anti-LPS antibodies were directed specifically against LPS of P. aeuruginosa. ELISAs were developed to determine the specific IgG sublclasses involved. The increase in IgG anti-LPS involved all four subclasses. Highest anti-LPS titers were seen with IgG1 and IgG4, but the largest relative increases were seen with IgG2 and IgG3.

Occurrence of a common lipopolysaccharide antigen in standard and clinical strains of Pseudomonas aeruginosa

The lipopolysaccharide (LPS) of Pseudomonas aeruginosa PAO1 contains two species of O polysaccharide termed A and B bands. The high-molecular-weight B-band LPS determines the O specificity of the bacterium, while the antigenically distinct A-band LPS consists of only shorter-chain polysaccharides. Seven hybridomas secreting A-band-specific monoclonal antibodies were produced and used to study the LPS of standard and clinical strains. Although A-band antibodies did not agglutinate any of the serotype strains presently in the International Antigenic Typing Scheme, Western immunoblots revealed that 11 of the 17 serotype strains possessed A-band LPS. In a group of 250 clinical isolates from patients with cystic fibrosis, 170 (68%) had A-band LPS on the basis of agglutination tests, but in silver-stained gels all were shown to be deficient in O-antigen-containing B band. Investigation of serial isolates from a single patient revealed a pattern of antigenic variation. During the course of the infection, serotypeable isolates became nontypeable, and the O antigen was replaced with A band as the major LPS antigen. These results suggest that A-band LPS may be the major LPS antigen in nontypeable clinical isolates and a common antigen among other P. aeruginosa strains.