Evaluation of polymerase chain reaction for direct detection of streptococcus pneumoniae in clinical samples & antimicrobial susceptibilities of the isolates

Author : Jyoti Chaudhary, Malini Shariff, Monorama Deb

Introduction: Streptococcus pneumoniae (S.pneumoniae) is an important cause of morbidity and mortality in people of extreme age. Drug resistant pneumococci are emerging and causing treatment failure. In the present study we evaluated Polymerase Chain Reaction (PCR) for rapid detection of S. pneumoniae directly from the clinical samples and antimicrobial susceptibilities of the culture isolates Material & methods: A total of 90 clinical samples from sterile sites were cultured. Direct detection of S.pneumoniae from the samples was done using PCR. The isolates were tested for antimicrobial susceptibility by disc diffusion method and Minimum Inhibitory Concentration (MIC) of penicillin was determined by microbroth dilution method. Results: Out of 90 samples 34 were positive for S. pneumoniae by PCR and 23 samples showed growth in culture. Of these 23 isolates, disc diffusion method showed that 61%, 0%, 13%, 35%, 83%, 4.3%, 0% of the isolates were resistant to penicillin, erythromycin, ciprofloxacin, tetracycline, co-trimoxazole, chloramphenicol, cefotaxime respectively and 13% erythromycin, 22% ciprofloxacin 9% tetracycline and 4.3% cotrimoxazole intermediate sensitive isolates were found. Only 4.3% isolates showed resistance to penicillin by microbroth dilution. Conclusion: PCR is a sensitive & rapid method for detection of S.pneumoniae. Penicillin resistance in S. pneumoniae should be confirmed by MIC testing to avoid false reporting.

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