Detection of the Streptococcus milleri group in sputum samples and investigation of its clinical significance in respiratory diseases

Abstract

Objectives: This study was conducted to investigate the detection rate of the Streptococcus milleri group (SMG) in sputum cultures and clarify its relevance to the clinical presentation of respiratory diseases. Methods: Data from sputum specimens that were submitted for routine clinical bacterial testing since 1997 at our hospital and classified using the Miller and Jones sputum classification system were analyzed based on SMG bacteria detection, SMG streptococci identification, and antimicrobial susceptibility testing. The relationships between SMG detection and respiratory disease and between SMG detection and bacterial volume were also analyzed in 23 patients with respiratory diseases. Results: SMG bacteria were most often detected in sputum samples that were macroscopically purulent (Miller and Jones classification P3) with a high number of leukocytes (Geckler classification G5). Some isolates also exhibited resistance to clindamycin and other antibiotics. SMG bacteria were detected in patients with pneumonia, pyothorax, and other respiratory diseases. Notably, an SMG-positive culture was observed in four patients with bronchial asthma. Conclusions: To our knowledge, this is the first report on the detection of SMG bacteria in patients with bronchial asthma. Considering the complications of asthma and chronic obstructive pulmonary disease overlap syndrome, SMG bacteria could contribute to exacerbation of the symptoms of these diseases. Given these findings, SMG bacteria, a well-established component of normal flora of the human oral cavity, may also serve as pathogens, especially in respiratory diseases.

Keywords

• streptococcus milleri group
• smg
• viridans streptococci
• oral flora
• respiratory disease