Bacterial behavior in human blood reveals complement evaders with some persister-like features
Fig 2
Complement is the main immune factor involved in bacterial clearance in HWB.
(A) Survival of P. aeruginosa strains in human plasma. Strains were incubated in plasma from different healthy donors (n = 10), and survival was measured based on CFU counts. ns: non-significant. When not stated, differences in survival were significant. Kruskal-Wallis test, p <0.001; Student-Newman-Keuls post-hoc test: p <0.05. Note similarities in survival profiles to those shown in Fig 1. (B) Heat-treating plasma prevents elimination of bacteria from HWB. Bacteria were incubated for 3 h in HWB from different donors (n = 6) with (hashed) and without (solid) heat-treatment to inactivate complement, or only with washed blood cells without plasma heating (dotted). The effect of this treatment on bacterial survival was assessed based on CFU counts. (C) Inhibition of MAC formation rescues P. aeruginosa strains from killing. Bacteria were incubated in a pool of human plasma for 3 h with (hashed) or without (solid) OmCI at 20 μg/mL (IHMA87 and PA14) or 40 μg/mL (CLJ1) and survival was measured based on CFU counts. Due to bacterial clumping, sonication was used to increase the accuracy of CFU measurement of IHMA87, as described in Methods. Data represent mean ± SD of three independent experiments. (D) Phagocytes are involved in the elimination of a limited number of strains. Bacteria were incubated for 3 h in HWB from different donors (n = 7) in the absence (solid) or presence of Cytochalasin D (hashed) or DNase I (dotted), to monitor the impact of these treatments on strain survival. (B) and (C): Kruskal-Wallis test, p <0.05; Student-Newman-Keuls post-hoc test: * p <0.05. Dots on the x-axis correspond to no detectable colonies.
doi: https://doi.org/10.1371/journal.ppat.1008893.g002