Bletilla striata Confers Antibacterial Activity and Pulmonary Protection in Senile Pneumonia Through Sortase A Inhibition

Abstract

Pneumonia caused by Streptococcus pneumoniae remains a serious threat to the elderly due to weakened immunity and limited treatment efficacy. This study investigates the antibacterial activity and therapeutic potential of Bletilla striata ethanolic extract (BSE) in a rat model of pneumococcal pneumonia. BSE demonstrated selective antibacterial activity against S. pneumoniae (MIC: 1.25 mg/mL) and significantly inhibited Sortase A (SrtA), a key bacterial virulence factor. In vivo, BSE improved body weight, reduced lung wet/dry ratios, and lowered serum ALP and LDH levels. It also diminished inflammatory cell infiltration in bronchoalveolar lavage fluid and decreased TNF-α, IL-1β, and IL-6 levels. Antioxidant markers SOD and GSH increased, while MDA levels declined. Histological analysis showed preserved lung architecture with reduced edema and cellular infiltration. Mechanistically, BSE suppressed the TLR4/NF-κB pathway. These findings indicate that BSE offers a dual benefit—direct antimicrobial action and modulation of inflammation and oxidative stress—highlighting its potential as a natural therapeutic for elderly patients with pneumonia.