Oxidative killing of encapsulated and nonencapsulated Streptococcus pneumoniae by lactoperoxidase-generated hypothiocyanite
Fig 5
LPO-derived hypothiocyanite kills both encapsulated and nonencapsulated Spn strains.
OSCN—mediated killing of Spn was tested in the cell-free system using 1st line TM against three encapsulated strains of Spn (TIGR4, D39 and EF3030) and their capsule-deficient, isogenic mutants (Δcap) in 4–5 independent experiments: n = 4 for TIGR4 and D39 Δcap, n = 5 for the other strains. Bacteria were incubated for 6 hrs with or without OSCN- generated by the LPO/SCN-/H2O2 system in presence or absence of catalase and bacterial killing was quantified by colony counts on BAP. Each symbol represents a separate, individual experiment, mean+/-S.E.M. is shown. ANOVA and Holm-Sidak's multiple comparisons test. Each experiment was done in biological triplicates and each biological replicate was tested in technical triplicates. Ns, not significant; *, p<0.05; **, p<0.01, ***, p<0.001. CFU, colony-forming unit; LPO, lactoperoxidase; OSCN-, hypothiocyanite; SCN-, thiocyanate; Spn, Streptococcus pneumonia; CAT, catalase.