Polyphosphate kinase 1 and the ocular virulence of Pseudomonas aeruginosa

PURPOSE. To determine the role of polyphosphate kinase 1 (PPK1) in the ocular virulence of Pseudomonas aeruginosa. METHODS. Using a mouse model of infection, P. aeruginosa strains PAO1, PAOM5 (an isogenic mutant of PAO1 deficient in PPK1), and PAOM5 + PPK1 (the mutant complemented with PPK1 on plasmid pHEPAK11) were compared for ocular virulence. These strains were also characterized with respect to traits associated with survival and pathogenicity in an ocular environment. RESULTS. The PPK1-deficient strain PAOM5 was significantly less virulent than either wild-type PAO1 or the complemented mutant (P < 0.016). Loss of virulence was not associated with serum sensitivity or diminished adherence to the cornea. However, PAOM5 has an increased susceptibility to oxidative stress and was cleared from corneal tissue significantly better (P < 0.006) than either the wild-type or restored strain. Furthermore, the PPK1-deficient mutant produced significantly less (P < 0.022) pyocyanin. CONCLUSIONS. PPK1 is essential for a successful ocular infection by P. aeruginosa. The loss of ocular virulence is probably due to the dysregulation of multiple genes, including those responsible for stress response.