Antibacterial effects of Kampo products against pneumonia causative bacteria

Community-acquired pneumonia is caused primarily by bacterial infection. For years, antibiotic treatment has been the standard of care for patients with bacterial pneumonia, although the emergence of antimicrobial-resistant strains is recognized as a global health issue. The traditional herbal medicine Kampo has a long history of clinical use and is relatively safe in treating various diseases. However, the antimicrobial effects of Kampo products against pneumonia-causative bacteria remain largely uncharacterized. In this study, we investigated the bacteriological efficacy of 11 Kampo products against bacteria commonly associated with pneumonia. Sho-saiko-To (9), Sho-seiryu-To (19), Chikujo-untan-To (91) and Shin'i-seihai-To (104) inhibited the growth of S. pneumoniae serotype 3, a highly virulent strain that causes severe pneumonia. Also, the growth of S. pneumoniae serotype 1, another highly virulent strain, was suppressed by treatment with Sho-saiko-To (9), Chikujo-untan-To (91), and Shin'i-seihai-To (104). Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against these strains ranged from 6.25-50 mg/mL and 12.5-25 mg/mL, respectively. Furthermore, Sho-saiko-To (9), Chikujo-untan-To (91), and Shin'i-seihai-To (104) suppressed the growth of antibiotic-resistant S. pneumoniae isolates. Additionally, Sho-saiko-To (9) and Shin'i-seihai-To (104) showed growth inhibition activity against Staphylococcus aureus, another causative agent for pneumonia, with MIC ranging from 6.25-12.5 mg/mL. These results suggest that some Kampo products have antimicrobial effects against S. pneumoniae and S. aureus, and that Sho-saiko-To (9) and Shin'i-seihai-To (104) are promising medicines for treating pneumonia caused by S. pneumoniae and S. aureus infection.