Abstract
A sample preparation method was developed to remove the effect of PCR inhibitors in blood cultures, and to concentrate the bacterial cells prior to PCR. This method was based on a combination of dilution, centrifugation, washing with NaOH and the addition of bovine serum albumin. The efficiency of this sample preparation was evaluated with
S. pneumoniae and
N. meningitidis added to a culture medium containing whole blood. The detection level of both bacteria was 1 CFU per ml of blood culture medium. Without this treatment, the PCR could not detect 10
7 CFU of
S. pneumoniae per reaction tube when 10 μl of culture medium containing human whole blood was added directly to the PCR mixture. When the sample preparation was evaluated with culture medium containing whole blood inoculated with approximately 0.3 CFU of
S. pneumoniae per ml and incubated at 37°C, a positive PCR product was detected after 8 h.