Identification and drug resistance of fungal pathogens in cystic fibrosis patients

Abstract

Cystic fibrosis (CF) is an autosomal genetic disease that causes infection in the lungs due to a lack of mucus clearance in the airways. Published studies on fungal pathogens in CF patients noted that the use of multiple antibiotics to treat drug-resistant bacterial infections in these patients has created an opening for colonization of the lung with fungal pathogens, and these organisms may also be drug-resistant. I hypothesized that fungal pathogens can be isolated from CF patient samples, and these fungal organisms will be resistant to antifungal therapies. Sputum samples were taken from CF patients from the Cystic Fibrosis Clinic in Oklahoma City, OK. Samples were plated using selective media to enrich for fungal growth. Following this, single colonies were isolated and cultured for inoculation of biochemical tests (API AUX20 C test strips) or for isolation of DNA. DNA samples were subjected to PCR for the ITS3 gene followed by gel electrophoresis to identify fungal ITS3 bands. Isolates with positive ITS3 bands were sequenced to identify the fungal species. In addition, MIC assays were conducted with antifungal drugs. Analysis of colonies tested by API test strips showed that several Candida species were present, and we further confirmed the species by sequencing the ITS3 gene. MIC assays were conducted with antifungal drugs fluconazole, caspofungin, and novel compound EIPE-1. MIC assays showed that some of these isolates were resistant to typical antifungal drugs and all were sensitive to EIPE-1. Further understanding the fungal pathogens and drug resistance in CF patients as well as identifying alternatives to current antifungal drugs could potentially prolong CF patient lifespan and decrease the severity of CF lung infections.