Fig. 4
E. faecium transposon mutants with a growth defect in human serum and an attenuated phenotype in a zebrafish infection model. a Ratios of the viable counts of five mutants compared to wild-type E. faecium before (blue bars) and after 24 h of growth in human serum (red bars) or BHI (yellow bars). The viable counts of wild-type E. faecium E745 were (3.52 ± 0.07) × 105/ml in the inocula, (2.92 ± 0.14) × 108/ml after 24 h of growth in serum and (1.20 ± 0.20) × 109/ml after 24 h of growth in BHI, respectively. Error bars represent the standard deviation of the mean of three independent experiments. Asterisks represent significant differences (***: p < 0.001, ****: p < 0.0001) as determined by a two-tailed Student’s t-test) between the mutant strains and wild-type. b Kaplan-Meier survival curves of zebrafish embryos upon infection with E. faecium. Infection was initiated by the injection of 1.2 × 104 CFUs of the manY_2::Gm and pyrK::Gm transposon mutants and the wild-type E. faecium E745 into the circulation of zebrafish embryos 30 h post fertilisation. The experiment was performed three times and the mutants were significantly different (**: p < 0.01) from the wild-type in each experiment as determined by the Log-rank (Mantel-Cox) test with Bonferroni correction for multiple comparisons. This figure represents the combined results of the three replicates for E. faecium E745 (n = 93 zebrafish embryos), manY_2::Gm (n = 92) and pyrK::Gm (n = 90)