The role of the molecular laboratory in the investigation of Streptococcus pneumoniae infections

The importance of infections with Streptococcus pneumoniae is being increasingly recognized. This has been emphasised by the emergence and international dissemination of penicillin-resistant strains. These factors challenge modern microbiologists to use molecular tools to speed the process of the diagnosis of S pneumoniae at each of the stages: rapid diagnosis, culture identification, and typing. The polymerase chain reaction (PCR) has been used to amplify a number of different targets for primary diagnosis of pneumonia, meningitis, otitis media, and bacteraemia. This may provide a rapid diagnosis in patients who have been partially treated with antibiotics and increase the diagnostic yield in clinical trials of antimicrobial agents and new vaccines. A new development is the use of PCR to rapidly determine penicillin susceptibility. Several different experimental protocols are reviewed. In the past serotyping using the capsule swelling, or Quellung reaction was the only typing method available. Recent insight into epidemiology and population genetics of S pneumoniae has shown that this technique is inadequate to study the transmission of this organism. New molecular typing techniques have been developed including Field version gel electrophoresis, ribotyping, restriction fragment end labeling, BOX PCR, and random amplification of polymorphic DNA. As these methods become available to clinicians, they will gain more understanding of the way in which this organism interacts with human populations.