Vol.64 No.4 July 2016
New insights based on a microfloral analysis -the significance of anaerobes in respiratory infections
Second Department of Internal Medicine, Nagasaki University School of Medicine, 1-7-1 Sakamoto, Nagasaki, Japan
Abstract
The mortality rate of pneumonia is gradually increasing concomitantly with the aging of the population in Japan, and pneumonia has been the third leading cause of death in Japan since 2011. It has been reported that over 95% of the deaths from pneumonia are elderly patients over 65 years of age. In addition, about 50% of hospitalized patients with pneumonia over 60 years of age have aspiration pneumonia, and the rate of aspiration increases with age. Therefore, proper treatment of pneumonia in the elderly and in cases of aspiration pneumonia is an important issue. Precise assessment of causative pathogens is extremely important for the first step towards an appropriate choice of antibiotics for the treatment of pneumonia. However, conventional cultivation methods are not totally adequate to estimate causative bacteria.
We have evaluated the bacterial flora in the respiratory samples obtained from patients with infectious diseases using the culture-independent molecular method, in collaboration with the Department of Microbiology, University of Occupational and Environmental Health, Japan. The microfloral analysis using the 16S rRNA gene was conducted as follows; a partial fragment of 16S rRNA gene (approximately 600 bp) was amplified with PCR using the universal primer pair and a clone library was constructed. Nucleotide sequences of 96 randomly chosen clones for each specimen were determined and the homology with our in-house database was assessed, then the percentages of detected bacterial phylotypes were identified.
This microfloral analysis of the bronchoalveolar lavage fluid obtained from patients with community-acquired pneumonia (CAP) and healthcare-associated pneumonia (HCAP) has so far showed that anaerobes and oral bacteria were highly detected in addition to well-known pathogens of CAP or HCAP. Particularly in patients in whom no significant pathogens had been identified using conventional cultivation methods, anaerobes and oral bacteria were mainly detected as the predominant phylotypes by the microfloral analysis. In addition, oral streptococci were more frequently detected than anaerobes in CAP and HCAP patients with aspiration risk(s), indicating that oral streptococci were the most important in patients with aspiration pneumonia. Anaerobes have been reported as one of the important pathogens in patients with aspiration pneumonia, but there were no significant differences in anaerobe detection between patients with or without the risk of aspiration in our study.
In this review, I will talk about the significance of anaerobes in respiratory infections, especially in patients with "elderly pneumonia" and "aspiration pneumonia", based on the data of the microflora analysis.
Key word
pneumonia, 16S ribosomal RNA, clone library, anaerobes, Streptococcus
Received
January 12, 2016
Accepted
February 3, 2016
Jpn. J. Chemother. 64 (4): 647-651, 2016
