Characterization of unusual bacteria isolated from respiratory secretions of cystic fibrosis patients and description of Inquilinus limosus gen. nov., sp. nov

Abstract

Using a polyphasic approach (including cellular protein and fatty acid analysis, biochemical characterization, 16S ribosomal DNA sequencing, and DNA-DNA hybridizations), we characterized 51 bacterial isolates recovered from respiratory secretions of cystic fibrosis (CF) patients. Our analyses showed that 24 isolates belong to taxa that have so far not (or only rarely) been reported from CF patients. These taxa include Acinetobacter sp., Bordetella hinzii, Burkholderia fungorum, Comamonas testosteroni, Chryseobacterium sp., Herbaspirillum sp., Moraxella osloensis, Pandoraea genomospecies 4, Ralstonia gilardii, Ralstonia mannitolilytica, Rhizobium radiobacter, and Xanthomonas sp. In addition, one isolate most likely represents a novel Ralstonia species, whereas nine isolates belong to novel taxa within the alpha-PROTEOBACTERIA: Eight of these latter isolates are classified into the novel genus Inquilinus gen. nov. as Inquilinus limosus gen. nov., sp. nov., or as Inquilinus sp. The remaining 17 isolates are characterized as members of the family ENTEROBACTERIACEAE: The recovery of these species suggests that the CF lung is an ecological niche capable of supporting the growth of a wide variety of bacteria rarely seen in clinical samples. Elucidation of the factors that account for the association between these unusual species and the respiratory tract of CF patients may provide important insights into the pathophysiology of CF infection. Because accurate identification of these organisms in the clinical microbiology laboratory may be problematic, the present study highlights the utility of reference laboratories capable of identifying unusual species recovered from CF sputum.

FIG. 1.

Phylogenetic tree showing the position of the genus Inquilinus and isolate AU2539 within the Proteobacteria. The scalebar represents 10% sequence dissimilarity.