Postal sputum samples for clinical and research applications in chronic lung infections caused by Pseudomonas aeruginosa

Abstract Introduction Postal sputum sampling represents a potential strategy for patient-led, efficient, and regular sampling, yet little is known about the validity of posting samples for clinical and research purposes in bronchiectasis. This study aimed to validate postal sputum sampling for clinical and research applications in chronic P. aeruginosa infection. Methods Sputum was collected from 12 participants with bronchiectasis and known P. aeruginosa infection. Each sputum sample was divided into four aliquots: two were sent immediately for analysis with or without DNA-Shield (shield-fresh and non-shield-Fresh), while two were transported through the UK postal service, with or without DNA-Shield (shield-posted and non-shield-posted). All aliquots were sent at ambient temperature and subsequently processed for bacterial enumeration through selective culture, detailed antimicrobial susceptibility testing, quantitative PCR (qPCR), 16S microbiome sequencing, metabolomics, and proteomics. Results During postage, there was a median of four days (range, 2-7) between sample collection and processing. 7/12 patients were positive for P. aeruginosa by culture of fresh samples, with 100% agreement in posted samples. Postage did not affect cultured (p=0.81) or amplified load of P. aeruginosa (p=0.94), and no differences were observed in AST profiles across 140 isolates for P. aeruginosa cultured from fresh or posted samples. Metabolomics and proteomics revealed that variation between individuals was significantly greater than between fresh and posted samples, and no significant differences in microbial taxa were observed between samples. No differences were associated with the addition of DNA Shield by qPCR (p=0.19), however, freeze-thaw from -80{degrees}C increased amplified load (p=<0.01). Conclusions We found little evidence of an effect of postage on sputum positivity, recoverable load, AST profile, microbiome, proteome or metabolome in sputum samples. These data suggest postal sputum samples may be a valuable tool for clinical and research applications.