Determining the effect of postage on the recovery of cystic fibrosis pathogens from respiratory samples

Objectives: Regular microbiological surveillance of sputum to detect pathogens is a cornerstone of CF care In many CF centres, patients may be required to post samples to the clinic, due to difficulty producing sputum on demand or for enhanced surveillance outside of routine clinics This is increasingly important in light of the COVID-19 pandemic where many CF patients are unable to come into clinic due to shielding However, these samples may experience fluctuations in temperature and hence altering the microbiology of a sample before processing Here we report the impact of posting on the detection of common CF pathogens, and hence reliability of the culture reports Methods: Ninety-two sputum samples were collected from 72 adults with CF Samples were weighed, mixed and split One part was sent immediately to the microbiology lab and another was posted back to the lab through the post Postal samples were returned and processed after a mean of 5 days Aliquots at each stage were stored at -80oC for subsequent PCR-based analysis In this study, we compared clinical microbiology reporting for the paired-sputum samples Results: Overall prevalence for all organisms present in >10% of samples is shown in the Table Sensitivity of the different sample types to each species is given as percent positive samples compared to all positive samples Postal samples detected all Burkholderia cepacia complex, 92% of P aeruginosa (versus 93% for the clinic sample) and 74% of Aspergillus spp (versus 78% for the clinic sample) All other organisms were detected in postal samples at the same or higher rate as clinic samples Conclusions: Despite being in the post for a median of 5 days, there was little difference in the culture-based microbiology results Posting sputum samples therefore does not appear to reduce the identification of key CF microorganisms, which remain viable for several days after collection PCR-based analyses of these same samples is ongoing