Search

The pneumolysin (ply) gene is widely used as a target in PCR assays for Streptococcus pneumoniae in respiratory secretions. However, false-positive results with conventional ply-based PCR have been reported. The aim here was to study the performance of a quantitative ply-based PCR for the identification of pneumococcal lower respiratory tract infection (LRTI). In a prospective study, fibreoptic bronchoscopy was performed in 156 hospitalized adult patients with LRTI and 31 controls who underwent bronchoscopy because of suspicion of malignancy. Among the LRTI patients and controls, the quantitative ply-based PCR applied to bronchoalveolar lavage (BAL) fluid was positive at >/=10(3) genome copies/mL in 61% and 71% of the subjects, at >/=10(5) genome copies/mL in 40% and 58% of the subjects, and at >/=10(7) genome copies/mL in 15% and 3.2% of the subjects, respectively. Using BAL fluid culture, blood culture, and/or a urinary antigen test, S. pneumoniae was identified in 19 LRTI patients. As compared with these diagnostic methods used in combination, quantitative ply-based PCR showed sensitivities and specificities of 89% and 43% at a cut-off of 10(3) genome copies/mL, of 84% and 66% at a cut-off of 10(5) genome copies/mL, and of 53% and 90% at a cut-off of 10(7) genome copies/mL, respectively. In conclusion, a high cut-off with the quantitative ply-based PCR was required to reach acceptable specificity. However, as a high cut-off resulted in low sensitivity, quantitative ply-based PCR does not appear to be clinically useful. Quantitative PCR methods for S. pneumoniae using alternative gene targets should be evaluated.

The present study assessed the diagnostic usefulness of a multiplex PCR (mPCR) for Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae and Chlamydophila pneumoniae applied to bronchoalveolar lavage (BAL). Fibreoptic bronchoscopy was performed on 156 hospitalised adult patients with lower respiratory tract infection (LRTI) and 36 controls. BAL fluid was analysed with bacterial culture and mPCR. By conventional diagnostic methods, S. pneumoniae, H. influenzae, M. pneumoniae and C. pneumoniae were aetiological agents in 14, 21, 3.2 and 0% of the LRTI patients, respectively. These pathogens were identified by BAL mPCR in 28, 47, 3.2 and 0.6% of cases, respectively, yielding sensitivities of 86% for S. pneumoniae, 88% for H. influenzae, 100% for M. pneumoniae and 0% for C. pneumoniae, and specificities of 81, 64, 100 and 99% for S. pneumoniae, H. influenzae, M. pneumoniae and C. pneumoniae, respectively. Of the 103 patients who had taken antibiotics prior to bronchoscopy, S. pneumoniae was identified by culture in 2.9% and by mPCR in 31%. Among the controls, mPCR identified S. pneumoniae in 11% and H. influenzae in 39%. In lower respiratory tract infection patients, bronchoalveolar lavage multiplex PCR can be useful for identification of Streptococcus pneumoniae, Mycoplasma pneumoniae and Chlamydophila pneumoniae. The method appears to be particularly useful in patients treated with antibiotics.