Fig. 3

Influence of antibiotic treatment on the recovery of pathogen DNA following pathogen enrichment. a-b S. aureus was grown in human whole blood, followed by a 90 min incubation in the presence of antibiotics, and CFU counts as well as pathogen DNA were quantified as described in Materials and Methods. Spiked whole blood without adsorbent treatment served as control (ctrl.). ΔcT values and CFU counts are given relative to the reference (sample taken prior to the addition of antibiotics). Recovery of pathogen DNA was not influenced by CIP and CLI, while DNA recovery was increased after treatment with the cell wall active antibiotics VAN and PIP. CFU counts were significantly reduced for PIP, VAN, and CIP (bactericidal), or remained constant for CLI (bacteriostatic), confirming efficacy of antibiotic treatment. Data are presented as mean ± standard deviation (n = 18; paired t-test). c-d Upon incubation of spiked blood samples with VAN and CIP over 72 h, the recovery of pathogen DNA remained stable (VAN) or even increased (CIP), while no viable bacteria were detectable beyond 48 h (n = 4; Friedman repeated measures and Dunnett’s Method). e Scanning electron micrographs of S. aureus incubated for 24 h in the presence of VAN and CIP failed to provide evidence for cell wall degradation or reduced culture density, as compared to the untreated control. Scale bar, 5 μm. Data are given as mean ± standard deviation