The combination of PCR and serology increases the diagnosis of Pseudomonas aeruginosa colonization/infection in cystic fibrosis

Biomarkers in Cystic Fibrosis Lung Disease - A Review

Cystic fibrosis is a polymorphic disease, marked by multiple and difficult-to-treat respiratory exacerbations with severe evolution. The lung disease dictates the disease’s evolution and it must be diagnosed early and treated accordingly, but the diagnosis is sometimes challenging because of the lack of a sensible tool. In the era of the biomarkers, the need for a sensitive and reliable one would be extremely important, considering that inflammation secondary to infections produce irreversible structural changes in the cystic fibrosis lungs. The present paper reviews the studied biomarkers in inflammation and infection with potential role in cystic fibrosis lung disease.

Upper Airway Findings and Markers of Lung Disease Progression in Patients with Cystic Fibrosis

Introduction  Cystic fibrosis (CF) is a genetic disease that limits the quality of life mainly due to respiratory symptoms. The relationship between findings of the upper airways and CF lung disease is not yet completely understood. Objective  The aim of the present study is to describe the most frequent nasal findings and pathogens in patients with CF and investigate the association between the findings of the upper respiratory tract and markers of lung disease progression. Methods  Retrospective study in patients with CF from the Pediatric Pulmonology Department who underwent otorhinolaryngological evaluation between 2015 and 2017. Nasal endoscopy and nasal swab collection were part of the evaluation. The severity markers used were: percentage of predicted forced expiratory volume in the first second (FEV1%), body mass index (BMI) and the Shwachman-Kulczycki (SK) clinical score. Results  A total of 48 patients with CF were included. The mean of the predicted percentage of FEV1% was 83.36 ± 30.04. The average 14 and SK score 89.11 ± 10.50. The bacteriology of the nasal swab was positive in 27 (54.1%) patients. Staphylococcus aureus was positive in 18 patients, Pseudomonas aeruginosa in 5, Pseudomonas cepacea in 3 and Stenotrophomonas maltophila in 1 patient. Nasal polyps were found in nine participants. Nasal polyps were found in nine participants and were associated with lower SK score. Conclusion  The pathogens found in the upper airway were, in order: S. aureus , P. aeruginosa , P. cepacea e S. maltophila . The presence of polyps in the nasal cavity showed statistical significance and appears to have association with the prognostic factor measured by the SK score.

A comparison of the CFHH criteria against the Leeds criteria in determining the Pseudomonas aeruginosa status among adults with cystic fibrosis

BACKGROUND

Pseudomonas aeruginosa (PA) status influences management decisions in cystic fibrosis (CF) but diagnostic approaches vary. We evaluated the ability of the CFHealthHub (CFHH) criteria, which consist of two major and four minor statements, in diagnosing chronic PA infection among adults with CF.

METHODS

In this retrospective cross-sectional analysis, we compared the CFHH criteria against the Leeds criteria. Data were collected between 1st January and 31^st December 2016 from all adults with CF receiving care at Sheffield, excluding those with lung transplantation (n = 7) or on ivacaftor (n = 13). The CFHH criteria PA status were cross-tabulated against the Leeds criteria, and clinical outcomes between chronic PA vs non chronic PA for both criteria were compared.

RESULTS

This analysis included 186 adults with CF (90 females, median age 27 years, median baseline FEV₁ 78.5%). The CFHH criteria diagnosed more cases of chronic PA (116/186, 62.4% vs 79/186, 42.5%), and 37/107 cases of non-chronic PA according to the Leeds criteria were deemed chronic PA by the CFHH criteria. The magnitude of difference in %FEV₁ decline between chronic PA vs non chronic PA was slightly greater for the CFHH criteria (-0.6%, 95% CI -1.8 to 0.6%) compared to the Leeds criteria (-0.2%, 95% CI -1.3 to 1.0%).

CONCLUSIONS

The CFHH criteria detected more chronic PA cases yet still retained similar levels of discrimination for health outcomes in comparison to the Leeds criteria. These findings provide preliminary evidence for the validity of the CFHH criteria among adults with CF.

Understanding Pseudomonas status among adults with cystic fibrosis: a real-world comparison of the Leeds criteria against clinicians' decision

Pseudomonas aeruginosa status influences cystic fibrosis (CF) clinical management but no 'gold standard' definition exists. The Leeds criteria are commonly used but may lack sensitivity for chronic P. aeruginosa. We compared clinicians' decision with the Leeds criteria in three adult CF centres. Two independent prospective datasets (Sheffield dataset, n = 185 adults; ACtiF pilot dataset, n = 62 adults from two different centres) were analysed. Clinicians involved in deciding P. aeruginosa status were blinded to the study objectives. Clinicians considered more adults with CF to have chronic P. aeruginosa infection compared to the Leeds criteria. This was more so for the Sheffield dataset (106/185, 57.3% with clinicians' decision vs. 80/185, 43.2% with the Leeds criteria; kappa coefficient between these two methods 0.72) compared to the ACtiF pilot dataset (34/62, 54.8% with clinicians' decision vs. 30/62, 48.4% with the Leeds criteria; kappa coefficient between these two methods 0.82). However, clinicians across different centres were relatively consistent once age and severity of lung disease, as indicated by the type of respiratory samples provided, were taken into account. Agreement in P. aeruginosa status was similar for both datasets among adults who predominantly provided sputum samples (kappa coefficient 0.78) or adults > 25 years old (kappa coefficient 0.82). Across three different centres, clinicians did not always agree with the Leeds criteria and tended to consider the Leeds criteria to lack sensitivity. Where disagreement occurred, clinicians tended to diagnose chronic P. aeruginosa infection because other relevant information was considered. These results suggest that a better definition for chronic P. aeruginosa might be developed by using consensus methods to move beyond a definition wholly dependent on standard microbiological results.

Application of six multiplex PCR's among 200 clinical isolates of Pseudomonas aeruginosa for the detection of 20 drug resistance encoding genes

Pseudomonas aeruginosa (P. aeruginosa) is a menacing opportunistic, nosocomial pathogen; become a growing concern as conventional antimicrobial therapy is now futile against it. Multi-drug resistant P. aeruginosa (MDRPA) has distinctive resistance mechanisms such as production of β-lactamases, repression of porin genes and over-expression of efflux pumps. The focus of this study is to standardize and application of multiplex PCR (mPCR) to detect the presence of betalactamase genes encoding bla_Tem, bla_OXA, bla_CTX-M-15, bla_Vim, bla_Ges, bla_Veb, bla_DIM, AmpC and Efflux pump genes encoding Mex A,B-oprM, Mex C,D-oprJ, Mex X,Y-oprN, oprD, nfxB, MexR. A total of 200 clinical isolates of P. aeruginosa were tested for the presence of the above mentioned genes genotypically through mPCR and characterized by phenotypic methods for ESBL and MBL production. Out of 200 isolates, 163 (81.5%) nfxB regulator gene, 102 (51%) MexA, 96 (48%) MexC, 93 (46.5%) MexB, 86 (43%) MexD, 81 (40.5%) OprM, 74 (37%) OprJ, 72 (36%) OprD and MexR, 53 (26.5%) Mex X and OprN, 49 (24.5%) MexY gene. Betalactamase genes 145 (72.5%) bla_Tem, 67 (33.5%) bla_OXA, 35 (17.5%) blaVim, 25(12.50%), 23 (11.50%) blaVeb, 21 (11.5%) blaGes, 14 (7%) Ctx-m and 10 (5%) AmpC and 5 (2.5%) blaDim-1 gene were tested positive by mPCR. Phenotypically 38 (19%) and 29 (14.5%) out of 200 tested positive for ESBL and MBL production. Application of this mPCR on clinical specimens is fast, accurate, specific and low-cost reliable tool for the screening, where culture negative Eubacterial PCR positive cases for an early molecular detection of drug resistance mechanism assisting the clinician to treat the disease with appropriate antibiotic selection.

A High Level of Soluble CD40L Is Associated with P. aeruginosa Infection in Patients with Cystic Fibrosis

Objective

The aim of this study was to evaluate whether the concentration of sCD40L, a product of platelet activation, correlates with the presence of Pseudomonas aeruginosa in the airway of patients with cystic fibrosis (CF) and to determine its possible clinical association.

Methods

Sixty patients with CF, ranging in age from 2 months to 36 years, were studied. The demographics, cystic fibrosis transmembrane conductance regulator (CFTR) genotype, spirometry measurements, radiographic and tomographic scans, platelet count in peripheral blood, sCD40L, IL-6, TNF-α and ICAM1 data were collected. Infection-colonization of the airway was evaluated using sputum and throat swab cultures; the levels of anti-Pseudomonas aeruginosa antibodies (Anti-PaAb) were evaluated.

Results

Patients with CF and chronic colonization had anti-PaAb values of 11.6 ± 2.1 ELISA units (EU) and sCD40L in plasma of 1530.9 ±1162.3 pg/mL; those with intermittent infection had 5.7 ± 2.7 EU and 2243.6 ± 1475.9 pg/mL; and those who were never infected had 3.46 ± 1.8 EU (p≤0.001) and 1008.1 ± 746.8 pg/mL (p≤0.01), respectively. The cutoff value of sCD40L of 1255 pg/mL was associated with an area under the ROC (receiver operating characteristic curve) of 0.84 (95% CI, 0.71 to 0.97), reflecting P. aeruginosa infection with a sensitivity of 73% and a specificity of 89%. Lung damage was determined using the Brasfield Score, the Bhalla Score, and spirometry (FVC%, FEV1%) and found to be significantly different among the groups (p≤0.001).

Conclusion

Circulating sCD40L levels are increased in patients with cystic fibrosis and P. aeruginosa infection. Soluble CD40L appears to reflect infection and provides a tool for monitoring the evolution of lung deterioration.

Assessment of serology and spirometry and the combination of both to complement microbiological isolation for earlier detection of Pseudomonas aeruginosa infection in children with cystic fibrosis

Background

The aim of this study was to assess whether serology and spirometry and the combination of both can complement culture-based detection for earlier recognition of Pseudomonas aeruginosa infection in children with cystic fibrosis.

Methods

A 4 year longitudinal prospective study that included 67 Slovenian children with cystic fibrosis with a mean age of 10.5 years was conducted. Serology, spirometry and a scoring system combining serology and spirometry were assessed and compared. Infection was confirmed with isolation of Pseudomonas aeruginosa from respiratory samples.

Results

There was a significantly positive correlation between serology and the combination of serology and spirometry and Pseudomonas aeruginosa isolation (P < 0.01 for both) and a significantly negative correlation between spirometry and Pseudomonas aeruginosa isolation (P < 0.05). An increase in serology for 1 ELISA unit increased the possibility of Pseudomonas aeruginosa isolation 1.6 times. A fall in FEV1% predicted for 10% increased the possibility of Pseudomonas aeruginosa isolation 9.8 times. Binary logistic regression analysis was used to determine the odds ratios and 95% confidence intervals for all three approaches. Serology had the highest specificity (0.80) and the combination of serology and spirometry the highest sensitivity (0.90). Both had a high negative predictive value (0.93 and 0.79 respectively).

Conclusion

Using serology and the combination of serology and lung function measurement can be beneficial for earlier detection of infection with Pseudomonas aeruginosa in children with cystic fibrosis when done simultaneously with standard culture-based detection from respiratory samples.

Detection of algD, oprL and exoA Genes by New Specific Primers as an Efficient, Rapid and Accurate Procedure for Direct Diagnosis of Pseudomonas aeruginosa Strains in Clinical Samples

Background:

Pseudomonas aeruginosa is an opportunistic pathogen that infects patients with cystic fibrosis, burning wounds, ophthalmic traumas and immunodeficiency.

Objectives:

The aim of the present study was to compare the efficiency of newly designed primer sets with some previously published primers for PCR detection of exoA, oprL and algD genes from P. aeruginosa.

Materials and Methods:

A total of 150 clinical specimens were inoculated into the routine and selective culture media for P. aeruginosa isolation. Specific primers were designed by bioinformatics analysis for detection of the virulence genes determinants, exoA, oprL and algD. The sequences of these three genes were obtained from NCBI and multiple alignments were performed to find the conserved sequences of each gene to design the primers. Multiple alignment and primer design steps were carried out by the AlleleID software, version 7.0.

Results:

Microbiological culture methods resulted 70 P. aeruginosa strains isolated from 70 of the 150 clinical specimens. The results of the PCR assay using the newly designed exoA, oprL and algD primer sets were positive in 68, 70 and 69 clinical samples which represent 97.2%, 100% and 98% sensitivity for each primer set, respectively. The PCR results using previously published exoA, oprL and algD primer sets were positive only in 57, 49 and 28 specimens that correspond to 81.5%, 70% and 40% sensitivity, respectively.

Conclusions:

The results of the present study showed that in comparison with previously published primer sets, P. aeruginosa infection can be diagnosed with higher sensitivity and specificity by the conventional PCR assay using the newly designed primers. It was also shown that the results of the PCR assay on clinical samples of severe infections became positive much earlier than the results of conventional culture method.

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

Detection of quorum sensing activity in the multidrug-resistant clinical isolate Pseudomonas aeruginosa strain GB11

A multidrug-resistant clinical bacteria strain GB11 was isolated from a wound swab on the leg of a patient. Identity of stain GB11 as Pseudomonas aeruginosa was validated by using matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS). Detection of the production of signaling molecules, N-acylhomoserine lactones (AHLs), was conducted using three different bacterial biosensors. A total of four different AHLs were found to be produced by strain GB11, namely N-butyryl homoserine lactone (C4-HSL), N-hexanoylhomoserine lactone (C6-HSL), N-octanoyl homoserine lactone (C8-HSL) and N-3-oxo-dodecanoylhomoserine lactone (3-oxo-C12-HSL) using high resolution liquid chromatography tandem mass spectrometry (LC-MS/MS). Of these detected AHLs, 3-oxo-C12-HSL was found to be the most abundant AHL produced by P. aeruginosa GB11.

Pseudomonas aeruginosa infection in patients with cystic fibrosis: scientific evidence regarding clinical impact, diagnosis, and treatment

Evidence-based techniques have been increasingly used in the creation of clinical guidelines and the development of recommendations for medical practice. The use of levels of evidence allows the reader to identify the quality of scientific information that supports the recommendations made by experts. The objective of this review was to address current concepts related to the clinical impact, diagnosis, and treatment of Pseudomonas aeruginosa infections in patients with cystic fibrosis. For the preparation of this review, the authors defined a group of questions that would be answered in accordance with the principles of PICO-an acronym based on questions regarding the Patients of interest, Intervention being studied, Comparison of the intervention, and Outcome of interest. For each question, a structured review of the literature was performed using the Medline database in order to identify the studies with the methodological design most appropriate to answering the question. The questions were designed so that each of the authors could write a response. A first draft was prepared and discussed by the group. Recommendations were then made on the basis of the level of scientific evidence, in accordance with the classification system devised by the Oxford Centre for Evidence-Based Medicine, as well as the level of agreement among the members of the group.

Bacterial sinusitis can be a focus for initial lung colonisation and chronic lung infection in patients with cystic fibrosis

A major purpose of treating patients with cystic fibrosis (CF) is to prevent or delay chronic lung infections with CF-pathogenic Gram-negative bacteria. In the intermittent stage, bacteria can usually be eradicated from the lungs with antibiotics, but following eradication, the next lung colonisations often occur with bacteria of identical genotype. This may be due to re-colonisation from the patient's paranasal sinuses. In our study, we found that approximately two-thirds of CF patients having sinus surgery (FESS) had growth of CF-lung-pathogenic Gram-negative bacteria in their sinuses (Pseudomonas aeruginosa, Achromobacter xylosoxidans, Burkholderia cepacia complex). The environment in the sinuses is in many ways similar to that of the lower respiratory tract, e.g. low oxygen concentration in secretions. Sinus bacteria are more difficult to eradicate than in the lungs, thus, having good conditions for adapting to the environment in the lungs. In the presence of bacteria, the environment of the sinuses differs from that of the lower respiratory tract by having a higher immunoglobulin A (IgA): IgG ratio, and reduced inflammation. We found a significant correlation between the concentration of IgA against P. aeruginosa (standard antigen and alginate) in nasal secretions and saliva and CF patients' infection status (not lung colonised, intermittently colonised or chronically lung-infected with P. aeruginosa). This supports the hypothesis that infections often originate in the sinuses and can be a focus for initial lung colonisation or for maintaining lung infections in CF patients. We are confident that anti-P. aeruginosa IgA can be used as an early supplementary tool to diagnose P. aeruginosa colonisation; P. aeruginosa being the microorganism causing most morbidity and mortality in CF patients. This is important since urgent treatment reduces morbidity when CF patients are early colonised with P. aeruginosa, however, there is a lack of diagnostic tools for detecting the early colonisation in the lungs and in the sinuses. We initiated a treatment strategy for CF patients to prevent sino-nasal bacteria being seeded into the lower airways: we recommended extensive functional endoscopic FESS with creation of sufficient drainage from all involved sinuses with subsequent i.v. antibiotics and at least 6 months of twice daily nasal irrigation with saline and antibiotics. By this strategy, sinus bacteria could be eradicated in a large proportion of patients. Essentially, growth of CF-pathogenic bacteria from the lower respiratory tract was decreased following the treatment. Furthermore, a number of patients have been free from CF-pathogenic bacteria for more than one year after FESS, and thus re-classified as "not lung colonised". We also corroborated that CF patients obtain an improved quality of life and reduction in their symptoms of chronic rhinosinusitis after FESS. It is primarily intermittently lung colonised CF patients with CF-pathogenic bacteria in their sinuses that seem to benefit from the treatment strategy. This is in accordance with the fact that we did not see a significant increase in lung function and only a small decrease in specific antibodies after FESS; a high systemic immune and inflammatory response and a decreasing lung function is generally not present in patients who primarily have sinus CF-pathogenic bacteria. It is important that guidelines are created for how CF patients with CF-pathogenic bacteria in the sinuses are to be treated, including criteria for who may likely benefit from FESS, and who may be treated exclusively with conservative therapy, e.g. saline and antibiotic irrigations.

Pseudomonas aeruginosa serology and risk for re-isolation in the EPIC trial

BACKGROUND

The prognostic value of Pseudomonas aeruginosa serology for antibiotic therapy in cystic fibrosis patients is not well understood.

METHODS

Using five antigens from two ELISAs, we assessed whether positive serology in CF patients participating in the multi-center Early Pseudomonas Infection in Children (EPIC) trial would predict treatment failure, time to pulmonary exacerbation and risk for recurrent P. aeruginosa isolation post eradication.

RESULTS

Baseline positive P. aeruginosa serology was not significantly associated with failure of initial P. aeruginosa eradication measured at week 10 (adjusted for baseline culture) but seropositivity to the antigens alkaline protease and exotoxin A was significantly associated with increased risk for recurrent P. aeruginosa isolation during the 60 week post eradication follow-up period (p=0.003 and p=0.001 respectively). There was no association between baseline seropositivity and time to pulmonary exacerbation.

CONCLUSION

P. aeruginosa serology may complement culture results in clinicians' efforts to successfully monitor recurrence of early P. aeruginosa in CF patients.

Secretory IgA as a diagnostic tool for Pseudomonas aeruginosa respiratory colonization

BACKGROUND

Pseudomonas aeruginosa sinusitis may be the focus for intermittent lung colonization in patients with cystic fibrosis (CF). The sinusitis may induce elevated IgA levels in nasal secretion and saliva against P. aeruginosa.

METHODS

120 CF patients chronically infected, intermittently colonized or without P. aeruginosa in the lungs participated in this cross-sectional study. IgA and IgG against P. aeruginosa sonicate and alginate were measured in nasal secretions, saliva, and in serum by ELISA.

RESULTS

The intermittently colonized patients had significantly higher IgA levels in nasal secretions and saliva than those without P. aeruginosa in the lungs, indicating that P. aeruginosa sinusitis may precede intermittent colonization and chronic infection of the lungs.

CONCLUSIONS

Specific IgA against P. aeruginosa in nasal secretions and saliva can contribute to differentiation between patients chronically infected, intermittently colonized, and without P. aeruginosa in the lungs. The diagnostic value of the IgA ELISA awaits a prospective study.

Nebulizers in cystic fibrosis: a source of bacterial contamination in cystic fibrosis patients?

OBJECTIVE

To determine whether nebulizers are a source of microbial contamination in patients with cystic fibrosis, as well as whether the technique and frequency of disinfection of these devices is appropriate.

METHODS

This was a cross-sectional, uncontrolled observational study. Samples were collected from 28 patients with cystic fibrosis. Samples were collected at the homes of the patients, who were not previously informed of the purpose of the visit. Three samples were collected from each patient: one from the nebulizer chamber, one from the mask/mouthpiece, and one from the patient (oropharyngeal swab /sputum). The samples were properly stored and taken for analyses. The patients, their parents, or their legal guardians completed a questionnaire regarding nebulizer cleaning and disinfecting methods.

RESULTS

We collected 84 samples from the 28 patients. Of those 28 patients, 15 (53.5%) were male. The median age of the patients was 11 years (range, 1-27 years). Of the 28 patients, 15 presented with positive oropharyngeal swab /sputum sample cultures. The most common bacterial isolates were Staphylococcus aureus (in 8 patients) and Pseudomonas aeruginosa (in 4 patients). Although the samples obtained from the nebulizers presented with various pathogens in culture, no specific species predominated. In 27 cases (96.7%), there were no associations between the samples obtained from the nebulizers and those obtained from the patients in terms of the results of the cultures. Cleaning and disinfection of nebulizers were inappropriate in 22 cases (78.6%).

CONCLUSIONS

In this sample of patients, despite the inappropriate disinfection techniques, nebulizers were not found to be a source of microbial contamination.

Using bacterial biomarkers to identify early indicators of cystic fibrosis pulmonary exacerbation onset

Acute periods of pulmonary exacerbation are the single most important cause of morbidity in cystic fibrosis patients, and may be associated with a loss of lung function. Intervening prior to the onset of a substantially increased inflammatory response may limit the associated damage to the airways. While a number of biomarker assays based on inflammatory markers have been developed, providing useful and important measures of disease during these periods, such factors are typically only elevated once the process of exacerbation has been initiated. Identifying biomarkers that can predict the onset of pulmonary exacerbation at an early stage would provide an opportunity to intervene before the establishment of a substantial immune response, with major implications for the advancement of cystic fibrosis care. The precise triggers of pulmonary exacerbation remain to be determined; however, the majority of models relate to the activity of microbes present in the patient's lower airways of cystic fibrosis. Advances in diagnostic microbiology now allow for the examination of these complex systems at a level likely to identify factors on which biomarker assays can be based. In this article, we discuss key considerations in the design and testing of assays that could predict pulmonary exacerbations.

Improved early diagnosis of Pseudomonas aeruginosa by real-time PCR to prevent chronic colonisation in a paediatric cystic fibrosis population

Early detection of Pseudomonas aeruginosa in children with cystic fibrosis is hampered by the need to process a sub-optimal specimen type, namely cough swabs, which are known to have a lower positive yield than sputa or more invasive samples. This delay in the detection of low levels of P. aeruginosa could potentially result in the loss of an opportunity to initiate early aggressive antibiotic therapy and result in chronic colonisation, with a poorer overall prognosis. Quantitative real-time PCR (qPCR) offers an opportunity to increase the detection rate of P. aeruginosa compared to traditional culture techniques. This study examined 500 cough swabs and 42 sputum samples from paediatric patients and showed that detection of P. aeruginosa could be increased in both sample types by 100% and 45% respectively. Overall the sensitivity was 100% and specificity of 58% when compared to culture as a gold standard. These results although initially promising require careful consideration both from a treatment and infection control standpoint as the significance of detection of very low levels of P. aeruginosa is unclear.

Evaluation of the efficacy of real-time polymerase chain reaction for the routine early detection of Pseudomonas aeruginosa in cystic fibrosis sputum and throat swab specimens

A longitudinal study of 2099 sputa and throat swabs received from 183 pediatric cystic fibrosis patients over a 29-month period was used to evaluate the efficacy of real-time polymerase chain reaction (PCR) for the early detection of Pseudomonas aeruginosa as compared to microbiologic culture. Real-time PCR resulted in an increased number of specimens identified as P. aeruginosa positive. The sensitivity of culture was 82% (373/453) and of PCR was 93% (420/453) when considering both positive culture and PCR results as true positives. Of the 80 specimens identified as PCR positive/culture negative for P. aeruginosa, the subsequent patient sample in 32.5% (26/80) of specimens concerned was identified as P. aeruginosa culture positive, suggesting that PCR has the potential to detect P. aeruginosa earlier than the microbiologic culture. Real-time PCR analysis found no evidence of the Liverpool and Manchester epidemic P. aeruginosa strains in the cohort examined. The findings of this study highlight the importance of specimen collection protocols to ensure that adequate samples are received at the laboratory for testing, thereby minimizing the potential for reporting of false-negative P. aeruginosa culture results.

Comparison of culture and qPCR for the detection of Pseudomonas aeruginosa in not chronically infected cystic fibrosis patients

Background

Pseudomonas aeruginosa is the major respiratory pathogen causing severe lung infections among CF patients, leading to high morbidity and mortality. Once infection is established, early antibiotic treatment is able to postpone the transition to chronic lung infection. In order to optimize the early detection, we compared the sensitivity of microbiological culture and quantitative PCR (qPCR) for the detection of P. aeruginosa in respiratory samples of not chronically infected CF patients.

Results

In this national study, we followed CF patients during periods between 1 to 15 months. For a total of 852 samples, 729 (86%) remained P. aeruginosa negative by both culture and qPCR, whereas 89 samples (10%) were positive by both culture and qPCR.

Twenty-six samples were negative by culture but positive by qPCR, and 10 samples were positive by culture but remained negative by qPCR. Five of the 26 patients with a culture negative, qPCR positive sample became later P. aeruginosa positive both by culture and qPCR.

Conclusion

Based on the results of this study, it can be concluded that qPCR may have a predictive value for impending P. aeruginosa infection for only a limited number of patients.

Early eradication of Pseudomonas aeruginosa in patients with cystic fibrosis

Pseudomonas aeruginosa (Pa) is the predominant organism infecting the airways of patients with cystic fibrosis (CF). This organism has an armamentarium of survival mechanisms that allows it to survive in the CF airway. Since colonization and chronic infection with Pa is associated with poorer lung function and increased morbidity and mortality, therapies that can prevent infection could significantly improve the lives of patients with CF. Numerous studies have examined the effects of treatment on the eradication of Pa as a means to ameliorate disease. This article outlines the pathophysiology and clinical implication of Pa acquisition, and reviews the existing treatment regimens aimed at early eradication of Pa in patients with CF.

Upper and lower airway cultures in children with cystic fibrosis: do not neglect the upper airways

BACKGROUND

Airways of cystic fibrosis (CF) patients are colonised with bacteria early in life. We aimed to analyse differences between results of simultaneously taken upper airway (UAW) and lower airway (LAW) cultures, to describe clinical characteristics of patients with positive versus negative cultures and to follow up the patients with P. aeruginosa positive UAW cultures.

METHODS

Bacteriological and clinical data from 157 children were collected during annual check up. The number of positive UAW and LAW cultures and correspondence between these results and clinical characteristics were analysed.

RESULTS

Positive LAW and UAW cultures were found in 79.6% and 43.9% of patients respectively (p<0.001). Patients with positive LAW cultures were significantly older (11.9 vs. 9.8years, p<0.05) and had more LAW symptoms (73.6% vs. 46.7%, p<0.05), especially when P. aeruginosa was found. Patients with positive UAW cultures (especially S. aureus) had more nasal discharge (50.7% vs. 25.0%, p<0.001). In 65% of patients with positive UAW and negative LAW culture for P. aeruginosa the next LAW became P. aeruginosa positive.

CONCLUSION

UAW cultures and LAW cultures differ in children with CF and there are differences in clinical characteristics between patients with positive versus negative culture results. P. aeruginosa positive UAW cultures appeared to precede positive LAW cultures in a substantial part of patients, suggesting some kind of cross-infection between the UAW and LAW.

Pseudomonas aeruginosa serological analysis in young children with cystic fibrosis diagnosed through newborn screening

BACKGROUND

With newborn screening (NBS) for cystic fibrosis (CF), eradication of Pseudomonas aeruginosa (PA) is possible if PA detection occurs early. A serological response to infection likely precedes culture positivity in CF patients, so PA serological testing is very appealing in this population. However, controversies continue to exist about serology testing, titer cutoffs for enzyme-linked immunosorbent assay (ELISA) antibody tests, and their value in children with CF.

METHODS

This longitudinal, prospective study collected respiratory secretions as oropharyngeal swabs or expectorated sputum for culture and also sera over 6 years in 69 patients diagnosed by NBS. Serology assessed PA antibody titers against cell lysate, exotoxin A, and elastase. A novel statistical approach with weighted receiver operating characteristic (ROC) curves was used to determine best antibody titer cutoff values to predict subsequent PA positive cultures.

RESULTS

Using these weighted ROC curves, the order of sensitivity was found to be cell lysate, exotoxin A, and then elastase while age-specific cutoffs were better than fixed cutoffs previously used. Age-specific serological cutoffs both predict and detect PA respiratory infections with a higher sensitivity and specificity. Serological responses to the PA antigens determined that a response to cell lysate occurs significantly earlier than culture positivity.

CONCLUSIONS

Age-specific serological cutoffs rather than fixed values against common PA antigens improve early PA identification in infants and young children diagnosed with NBS. Regular serological assessment with age-specific cutoffs in these children appears to be a worthy diagnostic tool.

Comparison of the sensitivity of culture, PCR and quantitative real-time PCR for the detection of Pseudomonas aeruginosa in sputum of cystic fibrosis patients

BACKGROUND

Pseudomonas aeruginosa is the major pathogen involved in the decline of lung function in cystic fibrosis (CF) patients. Early aggressive antibiotic therapy has been shown to be effective in preventing chronic colonization. Therefore, early detection is important and sensitive detection methods are warranted. In this study, we used a dilution series of P. aeruginosa positive sputa, diluted in a pool of P. aeruginosa negative sputa, all from CF patients--to mimick as closely as possible the sputa sent to routine laboratories--to compare the sensitivity of three culture techniques versus that of two conventional PCR formats and four real-time PCR formats, each targeting the P. aeruginosa oprL gene. In addition, we compared five DNA-extraction protocols.

RESULTS

In our hands, all three culture methods and the bioMérieux easyMAG Nuclisens protocol Generic 2.0.1, preceded by proteinase K pretreatment and followed by any of the 3 real-time PCR formats with probes were most sensitive and able to detect P. aeruginosa up to 50 cfu/ml, i.e. the theoretical minimum of one cell per PCR mixture, when taking into account the volumes used in this study of sample for DNA-extraction, of DNA-elution and of DNA-extract in the PCR mixture.

CONCLUSION

In this study, no difference in sensitivity could be found for the detection of P. aeruginosa from sputum between microbiological culture and optimized DNA-extraction and real-time PCR. The results also indicate the importance of the optimization of the DNA-extraction protocol and the PCR format.

Determining cystic fibrosis-affected lung microbiology: comparison of spontaneous and serially induced sputum samples by use of terminal restriction fragment length polymorphism profiling

Sampling of the lower airways of the adult cystic fibrosis (CF) lung has received insufficient detailed consideration, with the importance of sampling strategies for bacteriological outcome not known. Although spontaneously expectorated sputum (SES) samples are often used for diagnostic bacteriological analysis, induced sputum (IS) methods have advantages. This study examined whether significant differences in bacterial content were detected when using a culture-independent, molecular profiling technique to analyze SES or IS samples. Moreover, this work examined what trends relating to bacterial species distributions and reproducibility were found in sequentially induced sputum samples and what implications this has for pathogen detection. Terminal restriction fragment length polymorphism (T-RFLP) analysis was performed on a SES sample and 4 subsequent IS samples taken at 5-min intervals from 10 clinically stable, adult CF patients. This was repeated over 3 sampling days, with variability between samples, induction periods, and sampling days determined. A diverse range of bacterial species, including potentially novel pathogens, was found. No significant difference in bacterial content was observed for either SES or serial IS samples. On average, the analysis of a single sample from any time point resolved approximately 58% of total bacterial diversity achieved by analysis of an SES sample and 4 subsequent IS samples. The reliance on analysis of a single respiratory sample was not sufficient for the detection of recognized CF pathogens in all instances. Close correlation between T-RFLP and microbiological data in the detection of key species indicates the importance of these findings in routine diagnostics for the detection of recognized and novel CF pathogens.

Measuring and improving respiratory outcomes in cystic fibrosis lung disease: opportunities and challenges to therapy

Cystic fibrosis (CF) is a life-shortening disease with significant morbidity. Despite overall improvements in survival, patients with CF experience frequent pulmonary exacerbations and declining lung function, which often accelerates during adolescence. New treatments target steps in the pathogenesis of lung disease, such as the basic defect in CF (CF Transmembrane Conductance Regulator [CFTR]), pulmonary infections, inflammation, and mucociliary clearance. These treatments offer hope but also present challenges to patients, clinicians, and researchers. Comprehensive assessment of efficacy is critical to identify potentially beneficial treatments. Lung function and pulmonary exacerbation are the most commonly used outcome measures in CF clinical research. Other outcome measures under investigation include measures of CFTR function; biomarkers of infection, inflammation, lung injury and repair; and patient-reported outcomes. Molecular diagnostics may help elucidate the complex CF airway microbiome. As new treatments are developed for patients with CF, efforts should be made to balance treatment burden with quality of life. This review highlights emerging treatments, obstacles to optimizing outcomes, and key future directions for research.

Pseudomonas aeruginosa lasR mutants are associated with cystic fibrosis lung disease progression

BACKGROUND

Pseudomonas aeruginosa with mutations in the transcriptional regulator LasR chronically infect the airways of people with cystic fibrosis (CF), yet the prevalence and clinical implications of lasR mutant infection are unknown.

METHODS

In an exploratory study, we screened 166 P. aeruginosa isolates from 58 CF patients for LasR inactivation and mucoidy, and compared clinical characteristics among source patients.

RESULTS

lasR mutation prevalence was comparable to that of mucoidy, the best-described CF-adapted phenotype, but affected patients were on average approximately 2 years younger. In a regression analysis, lung function decline with age was worse among patients with lasR mutant infection than in those without, similar to the effect of mucoidy.

CONCLUSIONS

Culture positivity for lasR mutant P. aeruginosa may serve as a marker of early CF adaptive change of prognostic significance. Furthermore, as LasR inactivation alters susceptibility to antibiotics, infection with lasR mutant P. aeruginosa may impact response to therapy.

Molecular mechanisms of the cytotoxicity of ADP-ribosylating toxins

Bacterial pathogens utilize toxins to modify or kill host cells. The bacterial ADP-ribosyltransferases are a family of protein toxins that covalently transfer the ADP-ribose portion of NAD to host proteins. Each bacterial ADP-ribosyltransferase toxin modifies a specific host protein(s) that yields a unique pathology. These toxins possess the capacity to enter a host cell or to use a bacterial Type III apparatus for delivery into the host cell. Advances in our understanding of bacterial toxin action parallel the development of biophysical and structural biology as well as our understanding of the mammalian cell. Bacterial toxins have been utilized as vaccines, as tools to dissect host cell physiology, and more recently for the development of novel therapies to treat human disease.