Growth and survival profile of <i>E</i>. <i>faecalis</i> in human serum.

Growth and survival of E. faecalis OG1RF with (A) single Δefa, ΔmntH1, ΔmntH2 or (B) double ΔefaΔmntH1, ΔefaΔmntH2, ΔmntH1ΔmntH2, and triple ΔefaΔmntH1ΔmntH2 mutant strains in pooled human serum. (C) Serum was supplemented with 1 mM FeSO4 or 1 mM MnSO4, and survival of OG1RF, Δefa and ΔefaΔmntH1ΔmntH2 strains was recorded after 48 hours incubation. Control corresponds to serum without metal supplementation. Aliquots at selected time points were serially diluted and plated on BHI + Mn plates for CFU enumeration. The graphs show the average log10-transformed CFU mean and standard deviations of at least three independent experiments. In (A-B), mutant strains were compared against wild-type OG1RF by a two-way ANOVA with Dunnett’s multiple comparison test. (*p ≤ 0.05, **p ≤ 0.01,****p ≤ 0.0001). Significant differences at (^) 4 hours of incubation: *Δefa, *ΔefaΔmntH2, **ΔmntH1ΔmntH2; at (&) 8 hours of incubation: **ΔmntH2; at (ϕ) 24 hours of incubation: ****Δefa, **ΔmntH1 ****ΔefaΔmntH1, ****ΔefaΔmntH2, ****ΔefaΔmntH1ΔmntH2; at (ξ) 48 hours of incubation: ****Δefa, **ΔmntH1, ****ΔefaΔmntH1, ****ΔefaΔmntH2, *ΔmntH1ΔmntH2, ****ΔefaΔmntH1ΔmntH2. In (C), comparison of survival defects among strains and the effect of Fe or Mn supplementation on the same strain (#) versus untreated, or between parent and mutant strains (*) under the same conditions were assessed via two-way ANOVA with Tukey’s post-test on log10-transformed CFU values. (##p ≤ 0.01, ###p ≤ 0.001, **** or ####p ≤ 0.0001).