M.J. Ledson

Increased morbidity associated with chronic infection by an epidemic Pseudomonas aeruginosa strain in CF patients

Background: Chronic pulmonary infection with transmissible Pseudomonas aeruginosa strains in individuals with cystic fibrosis (CF) has been reported, raising issues of cross infection and patient segregation. The first such strain to be described (the Liverpool epidemic strain, LES) is now widespread in many UK CF centres. However, whether such infection carries a worse prognosis is unknown. To address this, the clinical course of a group of CF patients chronically infected by LES was compared with that in patients harbouring unique strains. Methods: Using P aeruginosa strain genotyping, two cohorts of CF patients attending the Liverpool CF service were identified who were LES positive or negative in 1998 and remained so until 2002. From these, two groups of 12 patients were matched in 1998 for age, spirometric parameters, and nutritional state and their clinical course was followed for 5 years. Patients chronically infected with Burkholderia cepacia were excluded. Results: Patients chronically infected with LES had a greater annual loss of lung function than those not chronically infected by LES (mean difference between groups −4.4% (95% CI −8.1 to −0.9; p<0.02)), and by 2002 their percentage predicted forced expiratory volume in 1 second (FEV1) was worse (mean 65.0% v 82.6%, p<0.03). Their nutritional state also deteriorated over the study period (mean difference between groups in body mass index −0.7 (95% CI −1.2 to −0.2; p<0.01)), such that by 2002 they were malnourished compared with LES negative patients (mean BMI 19.4 v 22.7, p<0.02). Conclusions: Chronic infection with the Liverpool epidemic P aeruginosa strain in CF patients confers a worse prognosis than infection with unique strains alone, confirming the need for patient segregation. Since this strain is common in many CF units, strain identification in all CF centres is essential. This can only be carried out using genomic typing methods.

Pseudomonas aeruginosa Population Diversity and Turnover in Cystic Fibrosis Chronic Infections

RATIONALE Pseudomonas aeruginosa isolates from chronic cystic fibrosis lung infections display multiple phenotypes indicating extensive population diversity. OBJECTIVES We aimed to examine how such diversity is distributed within and between patients, and to study the dynamics of single-strain phenotypic diversity in multiple patients through time. METHODS Sets of 40 P. aeruginosa isolates per sputum samples were analyzed for a series of phenotypic and genotypic characteristics. Population differentiation between patients, between samples within patients, and between isolates within samples was analyzed. MEASUREMENTS AND MAIN RESULTS We characterized 15 traits for a total of 1,720 isolates of an important and widely disseminated epidemic strain of P. aeruginosa from 10 chronically infected patients with cystic fibrosis multiply sampled during 2009. Overall, 43 sputum samples were analyzed and 398 haplotypes of the Liverpool Epidemic Strain were identified. The majority of phenotypic diversity occurred within patients. Such diversity is highly dynamic, displaying rapid turnover of haplotypes through time. P. aeruginosa populations within each individual sputum sample harbored extensive diversity. Although we observed major changes in the haplotype composition within patients between samples taken at intervals of several months, the compositions varied much less during exacerbation periods, despite the use of intravenous antibiotics. Our data also highlight a correlation between periods of pulmonary exacerbation and the overproduction of pyocyanin, a quorum sensing-controlled virulence factor. CONCLUSIONS These results significantly advance our understanding of the within-host population biology of P. aeruginosa during infection of patients with cystic fibrosis, and provide in vivo evidence for a link between pyocyanin production and patient morbidity.

Superinfection with a transmissible strain of Pseudomonas aeruginosa in adults with cystic fibrosis chronically colonised by P aeruginosa

Infection with transmissible strains of Pseudomonas aeruginosa can occur in uncolonised patients, but cross infection (superinfection) of patients already colonised withP aeruginosa has not been reported. With genotypic identification, we found superinfection by a multiresistant transmissible strain of P aeruginosa in four patients with cystic fibrosis (CF) who were already colonised by unique strains of P aeruginosa. No evidence of environmental contamination was found, but all patients became superinfected after contact with colonised individuals during inpatient stays. Inpatients with CF who are colonised with P aeruginosa should be separated by strain type. Such strain typing can only be reliably done by genomic methods, but this has resource implications.

Spread of an epidemic Pseudomonas aeruginosa strain from a patient with cystic fibrosis (CF) to non-CF relatives

Colonisation with Pseudomonas aeruginosa is common in adults with cystic fibrosis (CF) and there is increasing evidence that transmissible strains may cross colonise patients. However, transmission of these strains by social contact to healthy non-CF individuals has not been described. A case is presented where an adult CF patient colonised by an epidemic P aeruginosa strain infected her parents with subsequent morbidity.

Fluctuations in phenotypes and genotypes within populations of Pseudomonas aeruginosa in the cystic fibrosis lung during pulmonary exacerbations

Chronic respiratory infection by Pseudomonas aeruginosa contributes significantly to the morbidity and mortality associated with cystic fibrosis (CF). Using a series of phenotypic and genotypic tests on collections of 40 isolates per sputum sample, we analysed fluctuations within sputum populations of the P. aeruginosa Liverpool epidemic strain (LES) during pulmonary exacerbations. For each of three patients, three sequential sputum samples were analysed: (1) on presentation with exacerbation at the Regional Adult Cystic Fibrosis Unit, Liverpool; (2) a few days into intravenous antibiotic treatment; (3) when the patient had recovered. Fluctuations were observed in morphotype distribution, the production of virulence-associated quorum-sensing-dependent exoproducts (the phenazine compound pyocyanin and the elastase LasA), antibiotic susceptibility profiles and levels of auxotrophy. PCR assays were used to screen isolates for the presence of novel regions of the LES genome (islands and prophages) and to detect free phages. In one patient there was an increase in the prevalence of the LESGI-5 genomic island during the sampling period from 10 to 97.5 % carriage. LES phages 2-4 were detected in either the majority or all sputum samples tested, indicating widespread phage activity during the sampling period. The results of this study are indicative that significant fluctuations occur within P. aeruginosa populations during short periods of pulmonary exacerbation and intravenous antibiotic therapy.

Cross infection between cystic fibrosis patients colonised with Burkholderia cepacia

Whilst patient to patient spread of the respiratory pathogenBurkholderia cepacia is well recognised between patients with cystic fibrosis, prompting a strict segregation policy, cross colonisation between cystic fibrosis patients already infected withB cepacia has not been described and surveys show a very low incidence of patients with more than one strain. Five adult cystic fibrosis patients with B cepacia are presented who became cross colonised with a second B cepacia (UK epidemic) strain, four of whom then died, three from the cepacia syndrome. These cases show that, amongst segregated patients, cross colonisation with different B cepacia strains is possible, and even in these patients the acquisition of the UK epidemic strain may have a fatal outcome. In future it may be necessary to segregate cystic fibrosis patients colonised with the UK epidemic strain from all other patients with cystic fibrosis.

Outcome of Burkholderia cepacia colonisation in an adult cystic fibrosis centre

Background: Colonisation with Burkholderia cepacia is a poor prognostic indicator in subjects with cystic fibrosis (CF), but outcome prediction is impossible since patients are colonised by different strains with differing pathogenicity. The clinical course of a large cohort of CF patients colonised with UK epidemic (ET12) B cepacia was followed for 5 years and compared with that of the remaining patients in the clinic. Methods: Pulmonary function, nutritional state, and lung pathogen colonisation were recorded for 5 years before December 1997 or death for all 107 patients who had attended the Liverpool adult CF clinic since 1993. For each patient a time line from study entry to date of death or 1997 was constructed. In 1993 potential risk factors including age and sex were subjected to Cox proportional hazards analysis using the end point of mortality as the outcome variable. The analysis was supplemented by time varying covariables that described the change in FEV1, BMI, and colonisation status across time, and the excess risk associated with B cepacia colonisation was calculated. Subsequently, in those patients who died between 1993 and 1997, predictive factors for death were compared within groups using complete 5 year data. Results: Thirty seven patients had been colonised by epidemic B cepacia and these patients had four times the mortality of the remainder (p<0.01). In 1993 univariate predictors of mortality were age (alive 19.6 (0.64) v dead 23.8 (1.44); p<0.005) and baseline FEV1 (alive 68.6 (2.5)% predicted v dead 43.2 (4.8)%; p<0.001) with a trend for BMI (p=0.07). However, following time varying covariate Cox proportional hazards analysis, only lower FEV1 (hazards ratio 1.1, 95% confidence limits 1.06 to 1.14; p<0.001) and colonisation with B cepacia (hazards ratio 7.92, confidence limits 2.65 to 23.69; p<0.001) were identified as significant factors for death. Surviving B cepacia patients had similar initial lung function to the remaining surviving patients but had an accelerated loss of lung function over the study period (colonised –1.9% predicted per year v non-colonised –0.3% predicted per year; p<0.05). Deceased patients colonised with B cepacia had better spirometric results than the remaining deceased patients 5 years before death (p<0.05) but lost lung function at a greater rate than non-colonised patients (colonised –6.2% predicted per year v non-colonised –1.9% predicted per year; p<0.05). Conclusions: This study confirms the excess mortality associated with epidemic B cepacia colonisation and shows that those with poor spirometric values are at the greatest risk.

UK Lung Cancer RCT Pilot Screening Trial: baseline findings from the screening arm provide evidence for the potential implementation of lung cancer screening

Background Lung cancer screening using low-dose CT (LDCT) was shown to reduce lung cancer mortality by 20% in the National Lung Screening Trial. Methods The pilot UK Lung Cancer Screening (UKLS) is a randomised controlled trial of LDCT screening for lung cancer versus usual care. A population-based questionnaire was used to identify high-risk individuals. CT screen-detected nodules were managed by a pre-specified protocol. Cost effectiveness was modelled with reference to the National Lung Cancer Screening Trial mortality reduction. Results 247 354 individuals aged 50–75 years were approached; 30.7% expressed an interest, 8729 (11.5%) were eligible and 4055 were randomised, 2028 into the CT arm (1994 underwent a CT). Forty-two participants (2.1%) had confirmed lung cancer, 34 (1.7%) at baseline and 8 (0.4%) at the 12-month scan. 28/42 (66.7%) had stage I disease, 36/42 (85.7%) had stage I or II disease. 35/42 (83.3%) had surgical resection. 536 subjects had nodules greater than 50 mm3 or 5 mm diameter and 41/536 were found to have lung cancer. One further cancer was detected by follow-up of nodules between 15 and 50 mm3 at 12 months. The baseline estimate for the incremental cost-effectiveness ratio of once-only CT screening, under the UKLS protocol, was £8466 per quality adjusted life year gained (CI £5542 to £12 569). Conclusions The UKLS pilot trial demonstrated that it is possible to detect lung cancer at an early stage and deliver potentially curative treatment in over 80% of cases. Health economic analysis suggests that the intervention would be cost effective—this needs to be confirmed using data on observed lung cancer mortality reduction. Trial registration ISRCTN 78513845.

Long-Term Effect of Insulin Treatment in Cystic Fibrosis-Related Diabetes

Background: Although insulin treatment confers short-term benefit in cystic fibrosis-related diabetes (CFRD), few studies have compared its long-term effect on the clinical outcome. Objectives: In this study, we aimed to investigate the long-term impact of insulin treatment on pulmonary function, nutritional status and hospital admissions in patients with CFRD. Methods: We reviewed pulmonary function, body mass index (BMI) and hospital admissions 5 years before and 3 years after insulin therapy in 42 adult CFRD patients. Results: Prior to treatment, over a period of 5 years, the annual rate of change in forced expiratory volume in 1 s (FEV1) was –3.2%, forced vital capacity (FVC) –2.5%, and BMI –0.07%. At treatment of CFRD (baseline), the mean FEV1 was 51.6% predicted (range 24–96), FVC 66.4% (range 29–103) and BMI 19.5 (range 15.3–29.5). At 3 months following insulin treatment, there was a significant improvement in all parameters, which was maintained at 1 year for FEV1 (55.1%; p < 0.002), 2 years for FVC (72.1%; p < 0.01) and at 3 years for BMI (20.4%; p < 0.002). After 3 months, FEV1 declined at a rate similar to that before treatment (–3.2 vs. –3.1% per year; p = 0.77), such that the mean FEV1 after treatment returned to pretreatment baseline values at 34 months. There was no difference in the number of hospital admissions with insulin treatment. Conclusions: Insulin enhances the nutritional state and temporarily improves pulmonary function in CFRD patients, on average delaying the decline in FEV1 by 34 months.

Fosfomycin therapy for multiresistant Pseudomonas aeruginosa in cystic fibrosis.

BACKGROUND Increasing resistance to standard antibiotics has been demonstrated in CF patients colonised by Pseudomonas aeruginosa. The antibiotic Fosfomycin has a unique mode of action against this organism, and may protect against aminoglycoside mediated renal and ototoxic effects. However, there is little published experience of this drug in IV form, and it is not licensed for use in the UK. METHODS In combination with other antibiotics, we used Fosfomycin to treat 30 pulmonary exacerbations in 15 adult CF patients colonised by P. aeruginosa, mainly multiresistant strains. All patients gave informed consent. We cultured sputum prior to treatment and measured spirometry, renal function, and symptoms before and after treatment, and recorded any side effects. RESULTS One patient developed nausea and Fosfomycin treatment was withdrawn. The remaining patients showed clinical resolution of their chest exacerbations (mean FEV1% predicted: pre 41.1 vs. post 49.4, P<0.001). Although there was a statistical increase in plasma urea (pre 3.9 mmol/l vs. post 4.3, P<0.03), this was still within the normal range. Plasma creatinine was unchanged. CONCLUSIONS This study shows that IV Fosfomycin is well tolerated by adult patients with CF and can be useful in the treatment of those colonised with multiresistant P. aeruginosa.