Methanolic Extract of Moringa oleifera Seed Synergizes the Bactericidal Effect of Ampicillin, Cephalexin, and Amoxicillin/Clavulanic Acid Against Multidrug-Resistant Escherichia coli Isolated from Street-Vended Food

Background: Antibiotic drug resistance is a serious global health problem that threatens therapeutics against infectious diseases. As antibiotics become less effective every year, our objective was to evaluate the adjuvant activity of methanolic extracts of Moringa oleifera seed combined with antibiotics of clinical use against multidrug-resistant Escherichia coli isolated from street food samples searching for a new alternative to treat infectious diseases commonly treated with antibiotics. Methods: Secondary metabolites of M. oleifera seeds were obtained through maceration (methanol 80%) and detected following qualitative phytochemical assays. MIC, MBC and tolerance level were determined using microdilution tests. Antimicrobial activity was tested by sensitivity analysis, and the adjuvant activity was explored in combination with twelve antibiotics against the E. coli samples. Results: Alkaloids, phenolic compounds, flavonoids, and polyphenols were detected. MIC and MBC values ranged from 31.3 to 62 mg/mL and 62–125 mg/mL, respectively. The extract showed low antimicrobial activity against the multidrug-resistant E. coli, but the inhibitory capacity of ampicillin, cephalexin, and amoxicillin/clavulanic acid was significantly increased when combined with the plant extract. In contrast, the activity of ciprofloxacin, levofloxacin, tetracycline, polymyxin, and nalidixic acid decreased with the extract. Conclusion: Methanolic extracts of M. oleifera seeds represent a potential adjuvant for beta-lactams in the face of the growing problem of global antimicrobial resistance. This study represents the first steps in exploring the adjuvant capacity of plants against resistant environmental pathogens in Mexico.