Research Article: Optimized detection of bacteria in bloodstream infections

Date Published: June 26, 2019

Publisher: Public Library of Science

Author(s): Yajing Song, Peter Gyarmati, Henk D. F. H. Schallig.


Bloodstream infection (BSI) is a life-threatening condition characterized by the presence of pathogens in the blood. It is associated with increased morbidity and mortality, and has to be treated promptly as mortality increases with every hour of delayed treatment. Therefore, rapid and sensitive diagnosis of BSI is essential. The routine diagnostic method for BSI is blood culture, which can only detect culturable pathogens and takes several days to obtain results. The 16S rRNA gene is present in all bacteria and is commonly used as a target for universal bacterial detection in rapid molecular assays such as PCR. However, molecular detection of the 16S gene is hampered by the large amount of human DNA found in blood samples, making diagnostic results aspecific and less sensitive. We have optimized the selection of PCR primers targeting the 16S rRNA gene to avoid cross-reaction with human DNA background. The developed method increases specificity and sensitivity for pathogen diagnosis, and provides rapid and accurate pathogen detection for rare bacterial DNA in the presence of abundant host DNA.

Partial Text

Bloodstream infection (BSI) is a severe medical condition associated with increased morbidity and mortality worldwide, with and incidence of 80–200 per 100,000 annually [1]. The routine detection method of BSI is blood culture, and the most commonly detected bacterial strains are Escherichia coli, Staphylococcus aureus and Streptococcus pneumoniae [1]. Blood culture can only detect culturable pathogens, and it takes several days to perform. Molecular methods can also be used for diagnosing BSI: they can be executed in a few hours, and can detect a wide variety of bacteria by targeting multiple strains using specific probes or universal marker genes [2].

Rapid, sensitive and specific detection of pathogens is crucial in BSI cases. Antimicrobial treatment has to be started within hours after symptoms of BSI develops, because delay in antimicrobial treatment is associated with increased mortality in BSI [13]. Accurate identification of pathogens is important as false positive results would promote antibiotic misuse, generation of antimicrobial resistance and dysbiosis of the indigenous microbiota [14].