Catherine Doherty

Evidence for transmission of Pseudomonas cepacia by social contact in cystic fibrosis

Pulmonary colonisation with Pseudomonas cepacia in patients with cystic fibrosis can be associated with increased morbidity and mortality. The modes of transmission of P cepacia are, however, unclear. We used selective media and phenotypic and genomic typing systems to investigate the acquisition of P cepacia by adults with cystic fibrosis. An analysis of isolates from 210 patients attending regional clinics in Edinburgh and Manchester between 1986 and 1992 showed that the main cause of increased isolations of P cepacia from 1989 was the emergence of an epidemic strain that had spread between patients in both clinics. Epidemiological evidence indicated that social contact was important in spread of the epidemic strain within and between clinics. We suggest that guidelines to limit the acquisition of P cepacia should not be restricted to patients in hospital, and that intimate or frequent social contact is associated with a high risk of cross-infection.

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.

In vitro activities of meropenem, PD 127391, PD 131628, ceftazidime, chloramphenicol, co-trimoxazole, and ciprofloxacin against Pseudomonas cepacia.

In a study of 110 Pseudomonas cepacia isolates from patients without cystic fibrosis, the in vitro potencies of three new compounds, meropenem, PD 127391, and PD 131628, were comparable to those of ceftazidime and ciprofloxacin and exceeded those of chloramphenicol and co-trimoxazole. The MICs of ceftazidime, ciprofloxacin, meropenem, and the PD compounds for 90% of strains tested were < or = 4 micrograms/ml, whereas they were 32 micrograms/ml for chloramphenicol and co-trimoxazole. Data for 20 isolates from patients with cystic fibrosis indicated that the isolates were less susceptible to all seven antibiotics tested, with the most active compounds being meropenem and PD 127391.

Atorvastatin as a stable treatment in bronchiectasis: a randomised controlled trial

BACKGROUND Bronchiectasis is characterised by chronic cough, sputum production, and recurrent chest infections. Pathogenesis is poorly understood, but excess neutrophilic airway inflammation is seen. Accumulating evidence suggests that statins have pleiotropic effects; therefore, these drugs could be a potential anti-inflammatory treatment for patients with bronchiectasis. We did a proof-of-concept randomised controlled trial to establish if atorvastatin could reduce cough in patients with bronchiectasis. METHODS Patients aged 18-79 years were recruited from a secondary-care clinic in Edinburgh, UK. Participants had clinically significant bronchiectasis (ie, cough and sputum production when clinically stable) confirmed by chest CT and two or more chest infections in the preceding year. Individuals were randomly allocated to receive either high-dose atorvastatin (80 mg) or a placebo, given orally once a day for 6 months. Sequence generation was done with a block randomisation of four. Random allocation was masked to study investigators and patients. The primary endpoint was reduction in cough from baseline to 6 months, measured by the Leicester Cough Questionnaire (LCQ) score, with a lower score indicating a more severe cough (minimum clinically important difference, 1·3 units). Analysis was done by intention-to-treat. The trial is registered with ClinicalTrials.gov, number NCT01299181. FINDINGS Between June 23, 2011, and Jan 30, 2011, 82 patients were screened for inclusion in the study and 22 were excluded before randomisation. 30 individuals were assigned atorvastatin and 30 were allocated placebo. The change from baseline to 6 months in LCQ score differed between groups, with a mean change of 1·5 units in patients allocated atorvastatin versus -0·7 units in those assigned placebo (mean difference 2·2, 95% CI 0·5-3·9; p=0·01). 12 (40%) of 30 patients in the atorvastatin group improved by 1·3 units or more on the LCQ compared with five (17%) of 30 in the placebo group (difference 23%, 95% CI 1-45; p=0·04). Ten (33%) patients assigned atorvastatin had an adverse event versus three (10%) allocated placebo (difference 23%, 95% CI 3-43; p=0·02). No serious adverse events were recorded. INTERPRETATION 6 months of atorvastatin improved cough on a quality-of-life scale in patients with bronchiectasis. Multicentre studies are now needed to assess whether long-term statin treatment can reduce exacerbations. FUNDING Chief Scientists Office.

Mannose-binding lectin deficiency and disease severity in non-cystic fibrosis bronchiectasis: a prospective study

BACKGROUND Mannose-binding lectin (MBL) is a key component of innate immunity. MBL deficiency is common (10-30% of the general population depending on the definition used) and has been associated with disease progression in cystic fibrosis. We aimed to assess the effect of MBL deficiency on disease severity in non-cystic fibrosis bronchiectasis. METHODS We recruited patients with non-cystic fibrosis bronchiectasis and age-matched and sex-matched controls at a specialist bronchiectasis clinic in Edinburgh, UK. We assessed MBL function with genotyping (low-expressing genotype [deficiency] defined as homozygosity for exon 1 mutations [YO/YO] or compound heterozygosity [XA/YO]; YA/YO and XA/XA genotypes were defined as intermediate-expressing with all other genotypes defined as high-expressing) and serum measurements (deficiency defined with two parameters: <500 ng/mL or <200 ng/mL). We assessed rates of exacerbation, chronic bacterial colonisation, and lung function during 4 years of follow-up. FINDINGS We included 470 patients with bronchiectasis and 414 controls. MBL genotype frequencies and MBL serum concentrations did not differ between patients and controls. 55 (12%) patients with bronchiectasis had low-expressing genotypes. These patients had a mean of 2·7 exacerbations per year (SD 1·8), compared with 1·9 per year (1·2) for 135 patients with intermediate-expressing genotypes and 1·9 per year (1·3) for 280 patients with high-expressing genotypes (p<0·0001). Chronic colonisation with bacteria was most frequent in patients with low-expressing genotypes (47 [85%] patients vs 82 [61%] patients with intermediate-expressing genotypes and 183 [65%] patients with high-expressing genotypes; p=0·0041); especially P aeruginosa colonisation (19 [35%] patients vs 13 [10%] patients and 36 [13%] patients; p<0·0001). Patients with low-expressing genotypes were more likely to be admitted to hospital for severe exacerbations during follow-up (27 [49%] patients vs 42 [31%] patients and 87 [31%] patients; p=0·032). Patients with low-expressing genotypes also had increased scores for radiological severity and worse quality of life compared with the other two groups. MBL serum deficiency (<200 ng/mL) was associated with increased exacerbations, hospital admissions, and radiological severity. When <500 ng/mL was used as the definition of deficiency, the associations with exacerbation frequency and radiological severity were no longer significant. INTERPRETATION MBL might be an important modifier of disease severity in non-CF bronchiectasis. FUNDING UK Medical Research Council, UK Chief Scientists Office.

Garlic Revisited: Antimicrobial Activity of Allicin-Containing Garlic Extracts against Burkholderia cepacia Complex

The antimicrobial activities of garlic and other plant alliums are primarily based on allicin, a thiosulphinate present in crushed garlic bulbs. We set out to determine if pure allicin and aqueous garlic extracts (AGE) exhibit antimicrobial properties against the Burkholderia cepacia complex (Bcc), the major bacterial phytopathogen for alliums and an intrinsically multiresistant and life-threatening human pathogen. We prepared an AGE from commercial garlic bulbs and used HPLC to quantify the amount of allicin therein using an aqueous allicin standard (AAS). Initially we determined the minimum inhibitory concentrations (MICs) of the AGE against 38 Bcc isolates; these MICs ranged from 0.5 to 3% (v/v). The antimicrobial activity of pure allicin (AAS) was confirmed by MIC and minimum bactericidal concentration (MBC) assays against a smaller panel of five Bcc isolates; these included three representative strains of the most clinically important species, B. cenocepacia. Time kill assays, in the presence of ten times MIC, showed that the bactericidal activity of AGE and AAS against B. cenocepacia C6433 correlated with the concentration of allicin. We also used protein mass spectrometry analysis to begin to investigate the possible molecular mechanisms of allicin with a recombinant form of a thiol-dependent peroxiredoxin (BCP, Prx) from B. cenocepacia. This revealed that AAS and AGE modifies an essential BCP catalytic cysteine residue and suggests a role for allicin as a general electrophilic reagent that targets protein thiols. To our knowledge, we report the first evidence that allicin and allicin-containing garlic extracts possess inhibitory and bactericidal activities against the Bcc. Present therapeutic options against these life-threatening pathogens are limited; thus, allicin-containing compounds merit investigation as adjuncts to existing antibiotics.

The changing epidemiology of Burkholderia species infection at an adult cystic fibrosis centre

BACKGROUND This study reviews the impact of changing infection control practices at the Manchester Adult Cystic Fibrosis Centre (MACFC) upon the epidemiology of Burkholderia species infections. METHODS We reviewed strain and genomovar typing of all available Burkholderia isolates at our centre between 1983-2006. RESULTS The incidence/prevalence of infection with Burkholderia species between 1983-1990 was below 5%/9% each year. There was a rise in incidence/prevalence of Burkholderia species between 1991 and 1994 with a peak of 16.3%/31.2% in 1992. Following complete cohort segregation, the incidence has fallen to below 3% for all but one year and the prevalence has gradually reduced to 9.3% in 2005. Currently, there is an increase in the prevalence to 10.6% for the first time since 1994, predominantly due to patients with unique infections transferring into the unit from referring centres. The presence of unique strains now exceeds transmissible strains for the first time since 1991. CONCLUSIONS Infection control measures including patient segregation have controlled spread of transmissible B. cenocepacia strains, but not the acquisition of unique strains. Unique strains of Burkholderia species now account for the majority of new infections at the Manchester Adult Cystic Fibrosis Centre.

Incidence of common pyocin types of Pseudomonas aeruginosa from patients with cystic fibrosis and chronic airways diseases.

We sought evidence to determine if particular strains of Pseudomonas aeruginosa have a predilection for pulmonary colonisation in patients with cystic fibrosis (CF). The incidence of common pyocin types in non-CF isolates (74%) was similar to that noted in previous reports but differed significantly (X2 = 16.7, p less than 0.001) from the incidence of 40% observed in CF isolates. A retrospective analysis of respiratory isolates also indicated a relatively low incidence of common pyocin types (44%) in isolates from non-CF patients with chronic airways diseases and this incidence also differed significantly from that observed (73%) in other respiratory isolates from patients in the same hospital. These observations suggest that a subpopulation of P. aeruginosa exists which has a predilection for pulmonary colonisation in CF and other chronic pulmonary diseases and may assist in identification of factors affecting bacterial colonisation.

A Lung Segmental Model of Chronic Pseudomonas Infection in Sheep

Background Chronic lung infection with Pseudomonas aeruginosa is a major contributor to morbidity, mortality and premature death in cystic fibrosis. A new paradigm for managing such infections is needed, as are relevant and translatable animal models to identify and test concepts. We sought to improve on limitations associated with existing models of infection in small animals through developing a lung segmental model of chronic Pseudomonas infection in sheep. Methodology/Principal Findings Using local lung instillation of P. aeruginosa suspended in agar beads we were able to demonstrate that such infection led to the development of a suppurative, necrotising and pyogranulomatous pneumonia centred on the instilled beads. No overt evidence of organ or systemic compromise was apparent in any animal during the course of infection. Infection persisted in the lungs of individual animals for as long as 66 days after initial instillation. Quantitative microbiology applied to bronchoalveolar lavage fluid derived from infected segments proved an insensitive index of the presence of significant infection in lung tissue (>104 cfu/g). Conclusions/Significance The agar bead model of chronic P. aeruginosa lung infection in sheep is a relevant platform to investigate both the pathobiology of such infections as well as novel approaches to their diagnosis and therapy. Particular ethical benefits relate to the model in terms of refining existing approaches by compromising a smaller proportion of the lung with infection and facilitating longitudinal assessment by bronchoscopy, and also potentially reducing animal numbers through facilitating within-animal comparisons of differential therapeutic approaches.

Do processing time and storage of sputum influence quantitative bacteriology in bronchiectasis

This study aimed to establish whether the bacterial density of spontaneous sputum is affected by the time and mode of sample storage. Ten patients with bronchiectasis collected all sputum expectorated over 45 min. The samples were aliquoted and processed at 25 degrees C for qualitative and quantitative bacteriology at 1, 2, 4 and 6 h from expectoration. Further aliquots were stored at 25 degrees C, 4 degrees C and -20 degrees C for 24 and 48 h prior to processing. The species present was identified and median (interquartile range) sputum log(10) bacterial density (c.f.u. ml(-1)) calculated. All samples cultured grew Pseudomonas aeruginosa and for two patients Staphylococcus aureus additionally grew for all samples. There was no significant difference in P. aeruginosa density in samples processed at 1, 2, 4 and 6 h following expectoration [8.2 (7.8-8.3) c.f.u. ml(-1), 8.0 (7.8-8.3) c.f.u. ml(-1), 8.0 (7.9-8.2) c.f.u. ml(-1), 8.1 (7.9-8.2) c.f.u. ml(-1), respectively, P=0.392]. Storage for 24 and 48 h at 4 degrees C did not significantly change the bacterial load compared with processing at 1 h [8.03 (7.6-8.2) c.f.u. ml(-1), P=0.07, and 7.96 (7.49-8.22) c.f.u. ml(-1), P=0.09, respectively]. Storage for 24 and 48 h at -20 degrees C significantly reduced P. aeruginosa density [7.1 (6.1-7.7) c.f.u. ml(-1), P=0.005, and 6.9 (6.2-7.6) c.f.u. ml(-1), P=0.008, respectively]. Storage at 25 degrees C for 24 and 48 h was associated with a significant increase in bacterial load [8.3 (8.1-8.6) c.f.u. ml(-1), P=0.009, and 8.4 (8.1-8.5) c.f.u. ml(-1), P=0.03, respectively]. Bacterial density was not affected by storage for up to 6 h following expectoration at 25 degrees C; beyond this, storage at 4 degrees C is preferred.