Rapid detection of bacteraemia

Abstract

Bacteraemic sepsis has a high mortality that can be reduced by early diagnosis and initiation of appropriate antimicrobial therapy 1. Rapid confirmation of the diagnosis and identification of the causal agent provide guidance on the adequacy and duration of antimicrobial therapy and on the need for source investigation. Clinical microbiology laboratories have rightly placed great emphasis on this aspect of their practice. As causal organisms are usually present in low titre, direct microscopy is impractical and laboratories have generally relied on culture of blood in broth, which is relatively insensitive and too slow to influence initial management. Phenotypic methods for the identification and antimicrobial susceptibility testing (AST) of isolates have progressively improved over the last two decades, but still require significant periods of incubation. Similarly, commercial blood culture systems have been refined with better systems for automated detection of growth in broth, but still require incubation for up to five days and subculture for the isolation of pathogens. Constantly monitored blood culture systems and automated identification/AST are now the norm in most clinical laboratories. Although there will undoubtedly be further development of phenotypic methods, with incremental improvements in sensitivity and time-to-detection, research and development now concentrated on molecular detection methods has the potential to result in a paradigm shift in our approach to the microbiological diagnosis of this condition.