Evaluation of Alpinia officinarum Plant Extracts as Natural Quorum Quenchers against MDR Acinetobacter baumannii Isolates

Abstract

The roots of Alpinia officinarum were extracted in different solvents, initially methanol, followed by ethyl acetate, chloroform, and petroleum ether, and tested at three concentrations (25, 50, and 75 mg/mL) to isolate the active organic constituents. This study was performed to examine the inhibitory effect of the plant extract on the biological activities of multidrug-resistant (MDR) Acinetobacter baumannii, including biofilm formation, pellicle formation, motility, gelatinase and protease production, and quorum-sensing (QS) signalling. Fifty Acinetobacter spp. isolates were recovered from blood, urine, and cerebrospinal fluid of intensive care unit patients, of which 30 were identified as A. baumannii by API 20E and PCR (16S rRNA and blaOXA-51). The isolates showed high resistance to β-lactams (62.4%), moderate resistance to carbapenems (39%), and low resistance to fluoroquinolones (26.6%), and 84% were strong biofilm producers. Nine representative MDR isolates were treated with the extract fractions. Overall, the 75 mg/mL concentration of A. officinarum extract was the most effective against all isolates, and the methanol-derived fractions (petroleum ether and ethyl acetate) showed stronger inhibitory effects than the chloroform fraction. After treatment, biofilm and pellicle formation, motility, and AHL production were markedly reduced, and most isolates became susceptible to antibiotics to which they were previously resistant. These findings indicate that A. officinarum extracts are promising natural quorum quenchers and resistance-modifying agents against drug-resistant A. baumannii, although further studies are needed to identify the active antibacterial components of the extract.