Radiologic imaging in cystic fibrosis: cumulative effective dose and changing trends over 2 decades

Objective: With the increasing life expectancy for patients with cystic fibrosis (CF), and a known predisposition to certain cancers, cumulative radiation exposure from radiologic imaging is of increasing significance. This study explores the estimated cumulative effective radiation dose over a 17-year period from radiologic procedures and changing trends of imaging modalities over this period. Methods: Estimated cumulative effective dose (CED) from all thoracic and extrathoracic imaging modalities and interventional radiology procedures for both adult and pediatric patients with CF, exclusively attending a nationally designated CF center between 1992-2009 for > 1 year, was determined. The study period was divided into three equal tertiles, and estimated CED attributable to all radiologic procedures was estimated for each tertile. Results: Two hundred thirty patients met inclusion criteria (2,240 person-years of follow-up; 5,596 radiologic procedures). CED was > 75 mSv for one patient (0.43%), 36 patients (15.6%) had a CED between 20 and 75 mSv, 56 patients (24.3%) had a CED between 5 and 20 mSv, and in 138 patients (60%) the CED was estimated to be between 0 and 5 mSv over the study period. The mean annual CED per patient increased consecutively from 0.39 mSv/y to 0.47 mSv/y to 1.67 mSv/y over the tertiles one to three of the study period, respectively (P < .001). Thoracic imaging accounted for 46.9% of the total CED and abdominopelvic imaging accounted for 42.9% of the CED, respectively. There was an associated 5.9-fold increase in the use of all CT scanning per patient (P < .001). Conclusions: This study highlights the increasing exposure to ionizing radiation to patients with CF as a result of diagnostic imaging, primarily attributable to CT scanning. Increased awareness of CED and strategies to reduce this exposure are needed

Microbiota and Metabolite Profiling Reveal Specific Alterations in Bacterial Community Structure and Environment in the Cystic Fibrosis Airway during Exacerbation

Chronic polymicrobial infections of the lung are the foremost cause of morbidity and mortality in cystic fibrosis (CF) patients. The composition of the microbial flora of the airway alters considerably during infection, particularly during patient exacerbation. An understanding of which organisms are growing, their environment and their behaviour in the airway is of importance for designing antibiotic treatment regimes and for patient prognosis. To this end, we have analysed sputum samples taken from separate cohorts of CF and non-CF subjects for metabolites and in parallel, and we have examined both isolated DNA and RNA for the presence of 16S rRNA genes and transcripts by high-throughput sequencing of amplicon or cDNA libraries. This analysis revealed that although the population size of all dominant orders of bacteria as measured by DNA-and RNA-based methods are similar, greater discrepancies are seen with less prevalent organisms, some of which we associated with CF for the first time. Additionally, we identified a strong relationship between the abundance of specific anaerobes and fluctuations in several metabolites including lactate and putrescine during patient exacerbation. This study has hence identified organisms whose occurrence within the CF microbiome has been hitherto unreported and has revealed potential metabolic biomarkers for exacerbation

Microbiota and metabolite profiling reveal specific alterations in bacterial community structure and environment in the cystic fibrosis airway during exacerbation

Chronic polymicrobial infections of the lung are the foremost cause of morbidity and mortality in cystic fibrosis (CF) patients. The composition of the microbial flora of the airway alters considerably during infection, particularly during patient exacerbation. An understanding of which organisms are growing, their environment and their behaviour in the airway is of importance for designing antibiotic treatment regimes and for patient prognosis. To this end, we have analysed sputum samples taken from separate cohorts of CF and non-CF subjects for metabolites and in parallel, and we have examined both isolated DNA and RNA for the presence of 16S rRNA genes and transcripts by high-throughput sequencing of amplicon or cDNA libraries. This analysis revealed that although the population size of all dominant orders of bacteria as measured by DNA- and RNA- based methods are similar, greater discrepancies are seen with less prevalent organisms, some of which we associated with CF for the first time. Additionally, we identified a strong relationship between the abundance of specific anaerobes and fluctuations in several metabolites including lactate and putrescine during patient exacerbation. This study has hence identified organisms whose occurrence within the CF microbiome has been hitherto unreported and has revealed potential metabolic biomarkers for exacerbation.</p

Representative HPLC trace of metabolites from sputum taken from a CF patient during a period of stability (A) and presenting with pulmonary exacerbation (B).

<p>Regions are labelled to indicate a range were metabolites of interest that were recovered from samples. Specific concentrations of metabolites identified are detailed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0082432#pone.0082432.s009" target="_blank">Tables S4</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0082432#pone.0082432.s010" target="_blank">S5</a>.</p

Concentrations of lactate (i), pyruvate (ii), putrescine (iii) and palmitate (iv) detected in sputum samples taken from 26 CF patients during a period of stability and presenting with pulmonary exacerbation (A).

<p>Each dot represents an individual patient. Data are given as the average values measured in triplicate (metabolite concentrations are described as µM unless otherwise stated and means ± standard deviations are reported). (B) PLS-DA plots of metabolite profile of sputum taken from 26 CF patients during a period of stability and presenting with pulmonary exacerbation. Stable subjects (green) vs. exacerbated subjects (red); R² = 0.95, Q² = 0.93 for a two-component model. The ellipses represent the 95% confidence region. Permutation tests (n = 1,000) validated the model (p<0.001).</p

Relative abundances of bacterial orders identified as operational taxonomic units (OTUs) from the sequence reads generated from sputum samples of CF patients presenting with exacerbation.

<p>The coloured segments of each bar represent the proportion of reads mapping to different bacterial orders. Percentage of sequences from total DNA (A) or total transcribed RNA (B) are described. Details of clinical parameters and microbiological assessment of each of the sputum samples collected are described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0082432#pone.0082432.s008" target="_blank">Table S3</a>. Total bacterial density in each sputum sample examined is indicated as 16S rRNA copies/ml sputum as measured by quantitative PCR.</p

Bacterial community structures of samples from stable CF patients and those presenting with exacerbation as plotted based on Bray–Curtis (BC) distance metric.

<p>Each community from each sample is represented as a filled circle and coloured by class (green – total DNA extracted from CF patients presenting with exacerbation; red – total RNA extracted from CF patients presenting with exacerbation; magenta – total DNA extracted from stable CF patients; cyan – total RNA extracted from stable CF patients). BC sample clusters are based on the distribution of the bacterial orders found in an individual sample. A confirmation of differences between samples was validated using the ade4 permutation test. This determined the statistical significance of the BC; the ellipses represent the 95% confidence region.</p

Identification of anaerobic bacterial populations among sputum samples from CF patients presenting with exacerbation.

<p>Percentage sequences from DNA-based (A) and RNA-based (B) approaches are described. The coloured segments of each bar represent the proportion of reads mapping to different anaerobic bacterial orders.</p

Bacterial cis-2-unsaturated fatty acids found in the cystic fibrosis airway modulate virulence and persistence of Pseudomonas aeruginosa

There is an increasing appreciation of the polymicrobial nature of many bacterial infections such as those associated with cystic fibrosis (CF) and of the potentially important role for interspecies interactions in influencing both bacterial virulence and response to therapy. Patients with CF are often co-infected with Pseudomonas aeruginosa and other pathogens including Burkholderia cenocepacia and Stenotrophomonas maltophilia. These latter bacteria produce signal molecules of the diffusible signal factor (DSF) family, which are cis-2-unsaturated fatty acids. We have previously shown by in vitro studies that DSF from S. maltophilia leads to altered biofilm formation and increased resistance to antibiotics by P. aeruginosa; these responses of P. aeruginosa require the sensor kinase PA1396. Here we show that DSF signals are present in sputum taken from patients with CF. Presence of these DSF signals was correlated with patient colonization by S. maltophilia and/or B. cenocepacia. Analysis of 50 clinical isolates of P. aeruginosa showed that each responded to the presence of synthetic DSF by increased antibiotic resistance and these strains demonstrated little sequence variation in the PA1396 gene. In animal experiments using CF transmembrane conductance regulator knockout mice, the presence of DSF promoted P. aeruginosa persistence. Furthermore, antibiotic resistance of P. aeruginosa biofilms grown on human airway epithelial cells was enhanced in the presence of DSF. Taken together, these data provide substantial evidence that interspecies DSF-mediated bacterial interactions occur in the CF lung and may influence the efficacy of antibiotic treatment, particularly for chronic infections involving persistence of bacteria