WS20.1 Target minority bacterial population in cystic fibrosis lung microbiota

Abstract

Staphylococcus aureus is one of the most frequently encountered species in Cystic Fibrosis (CF) lung microbiota. However its frequent presence on agar plates from sputum samples of CF patients likely impaired the culture of other minority bacterial species that may be responsible for lung exacerbations. In order to discover this minority bacterial population, we examined the sputum sample of a CF patient using conventional culture dependent with or without inhibition of S. aureus growth with vancomycin and compare our results to culture independent molecular techniques. Using standard cultures as well as selective media at different physico-chemical conditions, we isolate Staphylococcus aureus in the majority of our culture conditions and media. Interestingly, after pre-incubation of the sample with Vancomycin to inhibit Staphylococcus aureus growth, we isolate new bacterial species (Granulicatella, Streptococcus, Rothia, Lactobacillus and Propionibacterium species), especially Actinomyces radicidentis, a rare bacterial species associated with endodontic infections never described in the context of CF. Using 16S rDNA PCR amplification and sequencing of subsequent clones, we identified Streptococcus, Granulicatella, Rothia, Abiotropha, Peptostreptococcus, Lachnospiraceae and Actinomyces along with S. aureus confirming the culture dependent findings. In conclusion, the use of various bacterial inhibitors to inhibit the growth of the dominant bacteria may help to discover the minority bacterial population that could be new or emerging species in the context of CF.