Background: The frequencies of etiologic bacterial agents of intrapleural infections reported until now have been widely varied, largely depending on the implemented detective methods. The aims of this study were to evaluate bacterial etiologies of bacterial pleurisy using a cultivation-independent method. Methods:Pleural fluids were collected from 42 febrile patients with hemipleural effusion. The bacterial flora was analyzed by a clone library method using amplified fragments of the 16S ribosomal RNA gene(rDNA) with universal primers in addition to conventional cultivation methods. Results:Forty-two specimens were obtained from 26 patients with bacterial pleurisy, seven with mycobacterial pleurisy, and nine with other pleural effusions. In the 26 bacterial cases, 16(61.5%) showed positive results for 16S rDNA sequencing analysis, of which 11(42.3%) were also positive for cultivation method. In seven(43.8%) of the 16 polymerase chain reaction-positive cases, anaerobic phylotypes were predominantly detected. Anaerobic phylotypes(six of these seven cases) were not detected by cultivation method. In nine(34.6%) of the 26 bacterial pleural cases, the results from the clone library methods were not accordant with those of the cultivation method. In seven of these nine cases, the discrepancies between the two detection methods were due to the existence of anaerobes. Conclusion:The clone library analysis using the 16S rDNA of pleural fluid showed a higher incidence of anaerobic bacteria in infectious pleurisy than that previously expected and provided additional bacterial information for cultivation methods.
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