Adjuvant Antibacterial Effects of Mouriri Elliptica Against Clinical Multidrug Resistant Gram‐Negative Bacterial Strains

Abstract

ABSTRACT Bacterial resistance to antibiotics represents a critical global health challenge, demanding urgent alternative strategies to manage infections caused by multidrug‐resistant (MDR) pathogens such as Acinetobacter baumannii, Staphylococcus aureus, Escherichia coli, and Klebsiella pneumoniae. A promising approach to address this problem involves the use of combination therapies, in which plant‐derived natural products represent an important reservoir of bioactive compounds with the potential to act as effective adjuvants, restoring or enhancing antibiotic efficacy. In this study, the ethanolic extract of Mouriri elliptica (EME) leaves was investigated for its antimicrobial and synergistic potential. EME showed moderate inhibitory activity against both standard and MDR strains, with the most significant effect against A. baumannii (MIC 78.1–312.5 µg/mL). Synergistic interactions were observed with conventional antibiotics, particularly ciprofloxacin against K. pneumoniae, reducing MIC values up to fifteen‐fold, and with ampicillin against E. coli and S. aureus. The extract also inhibited biofilm formation, with 68% inhibition for E. coli at 500 µg/mL and 72.04% for S. aureus at 250 µg/mL, with atomic force microscopy images corroborating these findings. LC‐MS profiling identified 41 compounds, including chlorogenic acid derivatives, flavonoids, ellagic acid derivatives, and triterpenes. Acute toxicity evaluation in mice at 2000 mg/kg revealed no adverse effects. Collectively, these findings support the potential of M. elliptica as a natural antibacterial adjuvant for enhancing the effectiveness of selected antibiotics against MDR pathogens, warranting further chemical, mechanistic, and in vivo investigation.