Diversity of Candida spp in adult CF patients

Introduction Pulmonary infections in Cystic Fibrosis (CF) are predominantly bacterial but the incidence and diversity of fungi as lung pathogens is increasing. Some fungi such as Aspergillus are known to cause significant morbidity in CF but other fungi have not yet been evaluated for their prevalence or clinical impact. This prospective, cross-sectional observational study set out to determine the prevalence and speciation of Candida spp in an adult CF cohort. Methods Sputum samples were collected from 36 patients attending the Manchester Adult CF Unit. After homogenization with Dithiothreiotol, 10µL of sputum was inoculated onto sabauroud (SAB) agar and chrome agar then incubated for 72 hours. Yeast colonies were sub-cultured into germ cell tubes for further microscopic identification. Remaining sputum was processed in a molecular laboratory using the MycXtra™ (Myconostica Ltd) fungal DNA extraction kit. Extracted DNA was stored for Candida DNA microarray analysis. Results SAB agar cultured yeast in 24 of 36 samples (67%). Chrome agar and germ cell culture identified > 1 Candida species in 7 of the 24 positive samples. 4 plates had species that were unidentifiable. Of those colonies identified the following species were found: Candida albicans/dublinensis 22, Candida glabrata 5, Candida tropicalis 1, Candida parapsilosis 1. These species are currently being tested for antifungal resistance. As there are unidentified species we are currently performing molecular identification with a Candida DNA microarray. Conclusion There is a wide diversity of Candida spp in adult CF sputum. Fungal-bacterial interactions are important. More research is required into the clinical relevance of these yeasts.