The bacteriological incidence of lung abscess using clone library analysis of 16S rRNA gene in bronchoalveolar lavage

Abstract

Background: The reported common pathogens of lung abscess are anaerobes, Streptococcus species and mixed infection. However, it is frequently difficult to detect anaerobes by sputum or bronchoalveolar lavage fluid (BALF) culture. The aim of the present study was to evaluate the bacteriological incidence of lung abscess in Japanese patients by means of bacterial floral analysis of the BALF specimens using clone library analysis of 16S rRNA gene. Patients and Methods: A total of 39 Japanese patients with lung abscess were enrolled, and the BALF specimens taken from the affected lesions were evaluated by both culture-independent molecular method and conventional cultivation methods. The molecular method was conducted as follows: approximately 600 base pairs of 16S ribosomal RNA genes were amplified by polymerase chain reaction using universal primers, then clone libraries were constructed. Nucleotide sequences of randomly chosen 96 clones for each specimen were determined and the homology with in-house database was searched to estimate the bacterial species. Results: The molecular method revealed that relatively high rate of anaerobes (54%) and S. anginosus group (18%) were detected. Mixed bacterial infection was observed in 76.9% of the patients, and 90.0% of anaerobes were found in patients with mixed infection. Conclusion: Our data suggests that anaerobes and S. anginosus group might play important roles in the pathogenesis of lung abscess.