Pandoraea species have emerged as opportunistic pathogens among cystic fibrosis (CF) and
non-CF patients. Pandoraea pulmonicola is the predominant Pandoraea species among Irish CF
patients. The objective of this study was to investigate the pathogenicity and potential
mechanisms of virulence of Irish P. pulmonicola isolates and strains from other Pandoraea
species. Three patients from whom the P. pulmonicola isolates were isolated have since died. The
in vivo virulence of these and other Pandoraea strains was examined by determining the ability to
kill Galleria mellonella larvae. The P. pulmonicola strains generally were the most virulent of the
species tested, with three showing a comparable or greater level of virulence in vivo relative to
another CF pathogen, Burkholderia cenocepacia, whilst strains from two other species,
Pandoraea apista and Pandoraea pnomenusa, were considerably less virulent. For all Pandoraea
species, whole cells were required for larval killing, as cell-free supernatants had little effect on
larval survival. Overall, invasive Pandoraea strains showed comparable invasion of two
independent lung epithelial cell lines, irrespective of whether they had a CF phenotype.
Pandoraea strains were also capable of translocation across polarized lung epithelial cell
monolayers. Although protease secretion was a common characteristic across the genus, it is
unlikely to be involved in pathogenesis. In conclusion, whilst multiple mechanisms of pathogenicity
may exist across the genus Pandoraea, it appears that lung cell invasion and translocation
contribute to the virulence of P. pulmonicola strains
