Ralstonia respiraculi sp. nov., isolated from the respiratory tract of cystic fibrosis patients

This study describes the identification and classification of a novel bacterium, Ralstonia respiraculi sp. nov., isolated from the respiratory tracts of cystic fibrosis (CF) patients in the United States. Five strains recovered from CF patients were analyzed using polyphasic taxonomy, including 16S rDNA sequencing, cellular protein analysis, fatty acid composition, and biochemical characterization. Four isolates were identified as belonging to a single novel Ralstonia species, designated R. respiraculi, with strain AU3313T designated as the type strain. The fifth isolate (AU3369) was phylogenetically related but appears to represent a distinct species. R. respiraculi is a Gram-negative, non-fermentative, motile rod that grows at 28, 32, and 37°C. The organism displays specific biochemical characteristics distinguishing it from other Ralstonia species and from common CF pathogens like Burkholderia cepacia complex and Achromobacter xylosoxidans. The findings expand knowledge of bacterial diversity in CF respiratory infections and provide diagnostic tools for identifying these organisms in clinical specimens.

Key findings

• Ralstonia respiraculi sp. nov. is a novel bacterial species isolated from respiratory secretions of cystic fibrosis patients, representing a previously unidentified Ralstonia sp. in the CF population.
• Four of five studied isolates belonged to R. respiraculi based on high 16S rRNA sequence similarity (98.8% among four strains), similar cellular protein profiles, and consistent fatty acid compositions.
• R. respiraculi can be differentiated from other Ralstonia species and clinically relevant CF pathogens by lacking β-galactosidase and lysine decarboxylase activities and failing to grow on Burkholderia cepacia-selective agar.
• The type strain AU3313T (LMG 21510T) and related isolates can be specifically identified using species-specific 16S rDNA PCR assays and conventional biochemical tests.
• A fifth isolate (AU3369) was closely related to R. respiraculi but showed distinct protein profiles, suggesting it represents another novel Ralstonia species pending further characterization.