A. Kevin Webb

Spread of a multiresistant strain of Pseudomonas aeruginosa in an adult cystic fibrosis clinic

We initiated a prospective surveillance study to investigate possible Pseudomonas aeruginosa cross-infection in our cystic fibrosis centre. We characterised isolates by pyocin typing and pulsed-field gel electrophoresis. 22 (14%) of 154 patients with chronic P aeruginosa had isolates with similar and new pyocin and pulsed-field gel electrophoresis types. The shared isolates showed unusual phenotypic features: they were non-pigmented, non-motile, and resistant to a number of antipseudomonal antibiotics. Cross-infection by a multiresistant P aeruginosa strain has therefore occurred in patients attending our cystic fibrosis centre. We recommend microbiological surveillance in other cystic fibrosis centres.

Intravenous antibiotics reduce the presence of Aspergillus in adult cystic fibrosis sputum

Background Pseudomonas aeruginosa and Aspergillus fumigatus frequently co-colonise the airways of patients with cystic fibrosis (CF). This study aimed to assess the impact of short-term administration of intravenous antipseudomonal antibiotics during CF exacerbations on the presence of Aspergillus. Methods Pre- and post-antibiotic sputum samples from 26 adult patients with CF and chronic Pseudomonas colonisation were analysed for the presence of Aspergillus by fungal culture, real-time PCR and galactomannan antigen (GM). Lung function (forced expiratory volume in 1 s and forced vital capacity % predicted) and blood levels of total IgE, specific A fumigatus IgE and specific A fumigatus IgG were measured at the start and end of antibiotics. Respiratory viral real-time PCR and bacterial community profiling using ribosomal intergenic spacer analysis (RISA) were performed to estimate concurrent changes in the lung microbiome. Results Aspergillus PCR and GM were more sensitive than culture in detecting Aspergillus species (culture 8%, GM 31%, PCR 77%). There was a significant decline in the presence of Aspergillus, measured both by PCR and GM index, following antibacterial therapy (PCR: median increase in crossing threshold 1.7 (IQR 0.5–3.8), p<0.001; GM: median fall in GM index 0.7 (IQR 0.4–1.6), p=0.016). All patients improved clinically with a significant increase in lung function (p<0.0001). RISA community analysis showed large changes in bacterial community similarity in 67% of patients following antibiotics. Viral RT-PCR demonstrated the presence of a concurrent respiratory virus in 27% of patients. Conclusions Intravenous antibiotics targeting Pseudomonas during CF pulmonary exacerbations have a negative impact on the presence of Aspergillus in sputum samples.

Long-term Change in Exercise Capacity, Body Mass, and Pulmonary Function in Adults With Cystic Fibrosis

STUDY OBJECTIVES Cross-sectional studies in patients with cystic fibrosis (CF) have shown that exercise capacity is correlated with pulmonary function and body mass. We have examined whether the same relationships are seen longitudinally in adults with CF. DESIGN Subjects who first performed progressive maximal cycle ergometry between 1986 and 1989 were retested using an identical protocol a mean of 6.3 years later. PARTICIPANTS AND SETTING Adults with CF attending a regional center. MEASUREMENTS AND RESULTS The principal exercise measures were peak oxygen uptake (VO2peak), ventilation (VEpeak), oxygen saturation, and heart rate. Spirometry, weight, and height were also recorded at each time point. At baseline, subjects had a mean age of 19.8 years, body mass index (BMI) of 19.0, FEV1 of 69% predicted, VO2peak of 1.56 L/min, and VEpeak of 48.9 L/min. At repeated testing after a mean interval of 6.3 years, the FEV1 had fallen significantly to 54% predicted (p < 0.001) and the BMI had risen significantly to a mean of 20.9 (p < 0.001). There were no significant differences in VO2peak or VEpeak, although VEpeak was a significantly higher proportion (72% vs 61%) of predicted maximal voluntary ventilation. CONCLUSIONS Adults with mild to moderate pulmonary dysfunction were able to increase body mass and maintain VO2peak despite a declining FEV1. VO2peak was not reduced by the decrease in FEV1 because VEpeak was unaffected. Improved nutrition may have contributed to maintaining fitness.

Incidence and clinical impact of respiratory viruses in adults with cystic fibrosis

Background Viral respiratory infection (VRI) is a common cause of pulmonary exacerbations in children with cystic fibrosis (CF). The importance of VRI in adult CF populations is unclear. Objective To determine the incidence and clinical impact of VRI among adults with CF. Methods One hundred adults with CF were followed up prospectively for 12 months. Sputum, nose swabs and throat swabs were collected every 2 months and at onset of pulmonary exacerbation. PCR assays for adenovirus, influenza A&B, human metapneumovirus, parainfluenza 1–3, respiratory syncytial virus and human rhinovirus were performed on each sample. Symptom scores, spirometry and inflammatory markers were measured at each visit. Results One or more respiratory viruses were detected in 191/626 (30.5%) visits. Human rhinovirus accounted for 72.5% of viruses. Overall incidence of VRI was 1.66 (95% CI 1.39 to 1.92) cases/patient-year. VRI was associated with increased risk of pulmonary exacerbation (OR=2.19; 95% CI 1.56 to 3.08; p<0.001) and prescription of antibiotics (OR=2.26; 95% CI 1.63 to 3.13; p<0.001). Virus-positive visits were associated with higher respiratory symptom scores and greater C-reactive protein levels. Virus-positive exacerbations had a lower acute fall in FEV1 than virus-negative exacerbations (12.7% vs 15.6%; p=0.040). The incidence of exacerbations, but not VRI, was associated with greater lung function decline over 12 months (−1.79% per pulmonary exacerbation/year; 95% CI −3.4 to −0.23; p=0.025). Conclusion VRI is common in adults with CF and is associated with substantial morbidity. Respiratory viruses are a potential therapeutic target in CF lung disease.

Clinical Outcome for Cystic Fibrosis Patients Infected With Transmissible Pseudomonas aeruginosa: An 8-Year Prospective Study

BACKGROUND Although there is now compelling evidence for cross-infection by strains of Pseudomonas aeruginosa at some specialist (cystic fibrosis [CF]) centers, the clinical impact of infection by transmissible strains is unclear. METHODS In an 8-year prospective study, we compared the clinical outcome of two groups of patients with CF infected by transmissible (n = 28) and sporadic strains (n = 52) of P aeruginosa. RESULTS There were no differences between the two groups in survival, annual changes in spirometry, or BMI. There were differences in requirements for IV antibiotic treatment (mean [SD]: 29.3 [21.9] days vs 53.1 [32.5] days) and hospitalization (median [range]: 11.6 [1.1, 49.3] days vs 23.3 [5.5, 103.6] days) between patients infected with sporadic and transmissible strains of P aeruginosa, respectively. CONCLUSIONS We conclude that infection by transmissible P aeruginosa does not increase mortality but is associated with increased health-care and antibiotic use for patients with CF.

IgE-Mediated Immune Responses and Airway Detection of Aspergillus and Candida in Adult Cystic Fibrosis

BACKGROUND The recovery of Aspergillus and Candida from the respiratory secretions of patients with cystic fibrosis (CF) is common. Their relationship to the development of allergic sensitization and effect on lung function has not been established. Improved techniques to detect these organisms are needed to increase knowledge of these effects. METHODS A 2-year prospective observational cohort study was performed. Fifty-five adult patients with CF had sputum monitored for Aspergillus by culture and real-time polymerase chain reaction and Candida by CHROMagar and carbon assimilation profile (API/ID 32C). Skin prick tests and ImmunoCAP IgEs to a panel of common and fungal allergens were performed. Lung function and pulmonary exacerbation rates were monitored over 2 years. RESULTS Sixty-nine percent of patient sputum samples showed chronic colonization with Candida and 60% showed colonization with Aspergillus. There was no association between the recovery of either organism and the presence of specific IgE responses. There was no difference in lung function decline for patients with Aspergillus or Candida colonization compared with those without (FEV₁ percent predicted, P = .41 and P = .90, respectively; FVC % predicted, P = .87 and P = .37, respectively). However, there was a significantly greater decline in FEV1 and increase in IV antibiotic days for those sensitized to Aspergillus (FEV₁ decline, P = .03; IV antibiotics days, P = .03). CONCLUSIONS Allergic sensitization is not associated with recovery of Candida or Aspergillus from the sputum of patients with CF. Aspergillus but not Candida sensitization is associated with greater lung function decline and pulmonary exacerbations.

Hydrogen cyanide concentrations in the breath of adult cystic fibrosis patients with and without Pseudomonas aeruginosa infection

Elevated concentrations of hydrogen cyanide (HCN) have been detected in the headspace of Pseudomonas aeruginosa (PA) cultures and in the breath of children with cystic fibrosis (CF) and PA infection. The use of mouth-exhaled breath HCN as a marker of PA infection in adults is more difficult to assess as some without PA infection generate HCN in their mouths. The analysis of breath exhaled via the nose, thereby avoiding volatile compounds produced in the mouth, will demonstrate elevated concentrations of HCN in adult CF patients chronically infected with PA. Using selected ion flow mass spectrometry (SIFT-MS), the mouth and the nose-exhaled breaths of 20 adult CF patients; 10 with chronic PA infection and 10 free from PA infection, were analysed for HCN. Acetone and ethanol were also measured as controls. SIFT-MS allows direct sampling and analysis of single breath exhalations, obviating the need to collect samples into bags or onto traps, which can compromise samples. HCN was detected in the mouth-exhaled breath of patients in both groups and in the nose-exhaled breath of patients with chronic PA infection. The difference in median (IQR) nose-exhaled HCN between the groups is statistically significant (11 (0.8-18) ppbv versus 0 (0-3.2) ppbv, p = 0.03). The concentrations of acetone and ethanol in nose-exhaled and mouth-exhaled breath are in keeping with previous studies. HCN in nose-exhaled breath is a biomarker of chronic airway infection with PA in adults with CF. Its application as a non-invasive diagnostic test for early PA infection warrants further investigation.

Rapid Detection of Emerging Pathogens and Loss of Microbial Diversity Associated with Severe Lung Disease in Cystic Fibrosis

ABSTRACT Respiratory infection in cystic fibrosis (CF) is polymicrobial, but standard sputum microbiology does not account for the lung microbiome or detect changes in microbial diversity associated with disease. As a clinically applicable CF microbiome surveillance scheme, total sputum nucleic acids isolated by a standard high-throughput robotic method for accredited viral diagnosis were profiled for bacterial diversity using ribosomal intergenic spacer analysis (RISA) PCR. Conventional culture and RISA were performed on 200 paired sputum samples from 93 CF adults; pyrosequencing of the 16S rRNA gene was applied to 59 patients to systematically determine bacterial diversity. Compared to the microbiology data, RISA profiles clustered into two groups: the emerging nonfermenting Gram-negative organisms (eNFGN) and Pseudomonas groups. Patients who were culture positive for Burkholderia, Achromobacter, Stenotrophomonas, and Ralstonia clustered within the eNFGN group. Pseudomonas group RISA profiles were associated with Pseudomonas aeruginosa culture-positive patients. Sequence analysis confirmed the abundance of eNFGN genera and Pseudomonas within these respective groups. Low bacterial diversity was associated with severe lung disease (P < 0.001) and the presence of Burkholderia (P < 0.001). An absence of Streptococcus (P < 0.05) occurred in individuals with lung function in the lowest quartile. In summary, nucleic acids isolated from CF sputum can serve as a single template for both molecular virology and bacteriology, with a RISA PCR rapidly detecting the presence of dominant eNFGN pathogens or P. aeruginosa missed by culture (11% of cases). We provide guidance for how this straightforward CF microbiota profiling scheme may be adopted by clinical laboratories.

Long-term non-invasive ventilation in cystic fibrosis — Experience over two decades ☆

BACKGROUND Non-invasive ventilation (NIV) is accepted as a bridge to lung transplantation in cystic fibrosis (CF) but there is little evidence to support its use outside this setting. METHODS We reviewed the records of all patients with CF who received domiciliary NIV at our centre between 1991 and 2010. RESULTS Of 47 patients studied, 36% underwent lung transplantation, 28% died without transplantation and 30% remain alive on NIV. Median duration of NIV was 16 months (range 2-90). Mean FEV(1) fell by 212 ml over the year before NIV but increased by 18 ml in the following year (p<0.01). Individual response to NIV was associated with lower baseline and more rapid decline in FEV(1). From 1991 to 2000, 70% underwent lung transplantation; from 2001 to 2010 only 27% were transplanted. CONCLUSIONS NIV may slow or reverse the decline in lung function in advanced CF. NIV is increasingly used beyond a bridge to transplantation at our centre.

Quantification of hydrogen cyanide and 2-aminoacetophenone in the headspace of Pseudomonas aeruginosa cultured under biofilm and planktonic conditions

Hydrogen cyanide (HCN) and 2-aminoacetophenone (2-AA; H2NC6H4COCH3) are possible biomarkers of pulmonary Pseudomonas aeruginosa (PA) infection that could be used in an exhaled breath test. All factors affecting their production need to be investigated, including the culture conditions: planktonic (free-floating) or biofilm (non-motile communities attached to a solid surface). In vivo, the change from planktonic to biofilm growth is signalled when a certain population density is reached. Using selected ion flow tube mass spectrometry, SIFT-MS, we have analysed HCN and 2-AA produced by 12 genotyped PA samples, cultured under both planktonic and biofilm conditions after 24, 48, 72 and 96 hours of incubation. The 12 samples included 3 different strains (genotypes), 50% of which had a mucoid phenotype and 50% had a non-mucoid phenotype. All samples produced significant concentrations of HCN; median (25th to 75th percentiles, IQR) concentration: 144 (61–512) parts-per-billion by volume (ppbv). Multivariate analysis showed HCN production varied dependent on genotype (p = 0.0014), culture duration (p = 0.005) and phenotype (p < 0.001) but not culture conditions (planktonic/biofilm). Much smaller concentrations of 2-AA were detected, median (IQR) concentration 1.8 (1.3–3) ppbv, despite which, multivariate analysis showed production was affected by genotype (p < 0.001) and culture duration (p = 0.007) but not phenotype or culture conditions. These data show that biofilm formation does not affect HCN production by PA and supports its use as a biomarker of PA infection. The concentrations of 2-AA are much lower than previous studies have shown. The reason for this is unclear but it raises questions about its suitability as a biomarker of PA infection.