Identification of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis from sputum samples of patients with community acquired pneumonia by polymerase chain reaction

Thesis Type: Postgraduate

Institution Of The Thesis: Orta Doğu Teknik Üniversitesi, Faculty of Arts and Sciences, Department of Biology, Turkey

Approval Date: 2005


Supervisor: AYŞE GÜL GÖZEN


The present work describes the evaluation of the value of polymerase chain reaction in diagnosis of pneumonia caused by the most common three bacterial pathogens; Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis from sputum of patients with community acquired pneumonia admitted to The Department of Pulmonary Diseases of Gulhane Military Medical Academy. In this study, 107 sputa from 142 patients with suspected community acquired pneumonia were used to survey the causative agents. Identification of the pathogens was performed by sputum Gram stain and conventional microbiological methods. Polymerase chain reaction was performed to investigate the presence of S.pneumoniae, H.influenzae, and M.catarrhalis for the same sputum samples as well. PCR products were processed by electrophoresis on 2% agarose gels with visualization of the amplicon with ethidium bromide and UV illumination. The 33 of 107 samples were positive in cultures and 67 in PCR. S.pneumoniae (48.5%) was the most common etiologic agent as to PCR analysis. The incidences of H.influenzae and M.catarrhalis were determined as 18.6%, and 4.7% respectively. The incidence of S.pneumoniae in patients with CAP and control group individuals were almost the same. The sputum PCR positives were higher than those reported carriage rates for these three microorganisms. 9 of 107 patients with PCR-positive had evidence of infection with pathogens other than S.pneumoniae. The results indicated that some of the PCR results were false positive due to oropharyngeal contamination. PCR testing of sputum samples for diagnosing pneumococcal pneumonia is unable to distinguish colonization from infection in some circumstances. To distinguish the colonization from infection, sputum Gram stain should be applied to the sputum specimens. Because of being faster and easier, PCR looks like becoming more reliable