Siderophore-Mediated Competition Between Cystic Fibrosis Pathogens Increases Virulence Factor Production

Achromobacter–Pseudomonas coinfection in cystic fibrosis airways is linked to worse lung function than either pathogen alone, or other CF bacterial coinfections, in 16S rRNA datasets.

• Why it matters: Coinfections may worsen CF disease, but the mechanisms and which pathogen pairings drive more severe outcomes remain unclear.
• What they did: Achromobacter spp. induced pyoverdine production by Pseudomonas aeruginosa PAO1 and clinical isolates on synthetic CF sputum medium with physiologically relevant iron; 17 of 21 Achromobacter strains (81%) did so, and 18 of 21 (86%) encoded an alcaligin biosynthetic gene cluster.
• The result: Alcaligin production by Achromobacter dolens RMS0405 during coculture was confirmed by mass spectrometry imaging, and increasing iron abolished pyoverdine induction; low-iron stress in PAO1 was linked to increased exotoxin A and other virulence factors.