Introduction and objectives Pseudomonas aeruginosa (Pa) is a significant respiratory pathogen. Research in Cystic Fibrosis cohorts has revealed transmissible strains, leading to heightened infection control protocols due to concerns of cross-infection. In patients with Non-Cystic Fibrosis Bronchiectasis (NCFB), the research is more limited. Our objectives were to investigate the strains found in our local NCFB population, and assess the occurrence of shared strains.
Methods Patients with NCFB and previous Pa in sputum culture consented to providing sputum for the study and review of their medical notes. Sputum samples from patients were processed in the usual manner and if Pa was isolated, 10 representative colonies per patient were stored for strain typing. Isolates were subjected to Random Amplification of Polymorphic DNA (RAPD). Distinct RAPD types were verified by electrophoresis on an Agilent Bioanalyzer and subsequent cluster analysis using GelCompar II software, and further investigated by Multi-Locus Sequence Typing (MLST).
Results Pa was obtained from 46 patients over 12 months providing 459 isolates. Co-existence of multiple strains was observed in two patients. Twenty patients (43%) had unique strains by RAPD and the remaining patients were clustered into 7 subgroups, defined as ≥90% homology by RAPD, using Pearson’s correlation analysis. The largest cluster showed a predominance of one MLST strain type identified as ST-17 (also known as “Clone C”) on the MLST database. In our cohort, 8 patients (17%) harboured Clone C, which is a higher prevalence than observed in previous UK studies of various patient cohorts (typically 2–6% prevalence). MLST analysis of smaller RAPD clusters identified other MLST strain types shared by 2 or 3 patients. As with Clone C, all the observed shared MLST strain types are globally distributed. MLST did not reveal any novel shared strains.
Conclusions Our cohort of patients with NCFB shows evidence of shared strains of Pa including a high prevalence of Clone C compared to previous national reports. Whilst the occurrence of shared strains may reflect their global distribution, we cannot rule out cross-infection between patients.
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