Fig. 1

Background and outline of the study. a Blood-borne pathogens can be detected using blood culture (detection of viable pathogens) or by molecular diagnostic methods, such as PCR (detection of pathogen DNA). PCR is either performed after extraction of total (host and pathogen) DNA or following pathogen enrichment to deplete human DNA as well as blood-borne inhibitors of PCR. We hypothesized that antibiotic treatment might induce disintegration and, consequently, incomplete pelleting of pathogens during sample processing with established pathogen enrichment protocols, resulting in partial loss of pathogen DNA. b Commonly used pathogen enrichment protocols comprise the selective lysis of blood cells by detergent treatment, pelleting of intact pathogens, and extraction of pathogen DNA using spin columns. c To assess the influence of antibiotic treatment on PCR-based pathogen detection following pathogen enrichment, S. aureus was spiked into human whole blood and grown for 4 h. Thereafter, spiked samples were incubated without further treatment (control) or received antibiotic treatment as described in Materials and Methods. For comparison, S. aureus was mechanically lysed using zirconium beads to achieve complete disintegration as described in Materials and Methods, spiked into whole blood, and processed in parallel to untreated and antibiotic-treated samples. CFU counts (viable pathogens) were determined in all samples, and pathogen DNA was quantified after pathogen enrichment as shown in panel b