Direct detection of Streptococcus pneumoniaeinclinical samples by molecular methods

Background: S.pneumoniaecan cause severe diseases, such asmeningitis, pneumonia and septicemia. Culture based methods, todetect this bacterium in clinical samples, is not sensitive enough. Molecularassaystargeting different genes, foraccuratedetection ofS.pneumoniae from isolates and clinical samples, remains problematic.Therefore weevaluated the efficiency of newconserved target genes fordetection of S. pneumoniaeby molecular methods. Methods: All received specimens, from patients with suspected pneumococcal disease, were cultured on blood agar with 5% sheep blood between February and July 2015. Isolates were identified using Gram stain, catalase, optochin and bile solubility tests. We used PCR and Tag Man based real-time PCR assays for detection of pneumococcal lytA, lytB and blp a genes from isolates and clinical samples. Results: We isolated 46 strains of S. pneumoniae from clinical specimens by culture based methods. All three mentioned genes detected in all the isolates and culture-positive samples by PCR and real-time PCR assays. Overall, 23.9% of culture-negative samples were positive by molecular assays. But different results were obtained with each of the three different genesin direct detection of pneumococcal DNA from culture-negative samples. Conclusion: Data from this research showed real-time PCR assay with targeting new conserved genes are sensitive methods for detection of S. Pneumonia from isolates and clinical samples.

Direct detection of Streptococcus pneumoniaeinclinical samples by molecular methods Keywords:

Streptococcus pneumoniae , PCR , real-time PCR , blpA , lytB , lytA