Evaluation of Pneumococcal Serotyping by Multiplex PCR and Quellung Reactions

Screening of 1,750 pneumococcal isolates for common serotypes by PCR was followed by Quellung reaction analysis of PCR-negative isolates with a comparison to the conventional (Quellung reaction only) approach. PCR agreed with Quellung reaction results for 99 % of isolates. The sequential PCR/Quellung reaction algorithm is accurate andmore cost-effective than the conven-tional approach. Streptococcus pneumoniae is a common cause of meningitis andpneumonia. The morbidity and mortality associated with in-vasive pneumococcal disease may be prevented by vaccination (1). Accurate pathogen serotyping provides important epidemiologic information to guide vaccine composition. The relative increase in nonvaccine serotypes since the introduction of the heptavalent pneumococcal conjugate vaccine underscores the need for ongo-ing surveillance (2–5). The Quellung reaction is the gold standard for distinguishing among the 93 known pneumococcal serotypes. Serotyping with the Quellung reaction is labor-intensive, requires expensive reagents, and can be difficult to interpret. An alternative to the Quellung reaction is serotype determina