Modified sequential multiplex PCR for determining capsular serotypes of invasive Streptococcus pneumoniae clinical isolates

Abstract number: P1345

Iraurgui P., Torres M.J., Cabrera E., Lepe J.A., Garnacho J., Obando I., Aznar J.

Objectives: The objective of this study was to evaluate a modified scheme of the sequential multiplex PCRs that devised the CDC for determining capsular serotypes of Streptococcus pneumoniae (J Clin Microbiol. 2006 44:124–131). The modified method was that the primer combinations used were adapted to the serotype distribution in Sevilla, Andalucía (Spain).

Methods: Two hundred fifty-seven invasive pneumococcal isolates obtained during 2004 to 2008 were tested using the modified multiplex PCR system, including 102 previously typed paediatric isolates by serological determination of capsular type, and 155 adult isolates. The primers were grouped into seven multiplex reactions, except for the serotype 10 primer that was not included in none of these reactions. Each reaction includes four primer pairs, and an internal positive control targeting all known pneumococcal cps operons. The main modification was to include primer pairs for the 1 and 5 serotypes in the first three reactions.

Results: In the paediatric isolates group, the concordance of the PCR results with conventional serotyping was 91%. Three of the 5 isolates for which serotypes could not be deduced were serotypes not included in the multiplex reaction scheme. The multiplex PCR typed 97.4% (151/155) of adult's isolates, and 93% (95/102) of paediatric isolates. In adult isolates, the modified multiplex PCR scheme, allowed us to type 73% of them, and with two additional PCRs 92%, while using the original scheme we would type 63% and 74.8% of the isolates respectively. In the paediatric isolates group, results obtained were the 73.5% versus 60%, with the first three reactions and 90% versus 72.5% with the two additional PCRs.

Conclusion: The modified sequential multiplex PCR is better adapted to the serotype distribution of invasive Streptococcus pneumoniae from our geographic area and this scheme, improve the efficiency of original CDC seven multiplex PCR.

Session Details

Date: 16/05/2009
Time: 00:00-00:00
Session name: 19th European Congress of Clinical Microbiology and Infectious Diseases
Location: Helsinki, Finland, 16 - 19 May 2009
Presentation type:
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