Antimicrobial and antioxidant potential of bamboo (Bambusa arundinacea) essential oil against multidrug-resistant ESBL-producing Escherichia coli and its application in a meat-model system

Abstract

The emergence and global dissemination of Multidrug-Resistant (MDR) and Extended-Spectrum β-Lactamase (ESBL)-producing Escherichia coli (MDR ESBL-EC) have substantially limited the effectiveness of conventional antibiotics, necessitating novel antimicrobial alternatives. The present study evaluated the antimicrobial, antioxidant and food-preservative potential of bamboo (Bambusa arundinacea) essential oil (BEO) against MDR ESBL-EC in a raw chicken meat model system. Initially, ten field isolates were screened by phenotypical, biochemical and molecular (species-specific uidA gene PCR) methods for confirmation of E. coli. ESBL production was confirmed by double disc synergy test, combination disc method, and broth microdilution assay, whereas, MDR phenotype was evaluated by Kirby-Bauer disc diffusion assay following which three MDR isolates (MDR ESBL-1, MDR ESBL-2, and MDR ESBL-3) were selected for further investigation. FTIR analysis of BEO revealed a terpenoid-rich profile, while GC-MS identified β-caryophyllene (29.17%), α-copaene (17.63%) and trans-cinnamaldehyde (16.68%) as major constituents. BEO exhibited potent in vitro antibacterial activity against the MDR ESBL-EC isolates, producing inhibition zones of 31.33-36.33 mm with MIC/MBC ratios 0.156-0.3125. Time-kill assays revealed rapid bactericidal action, achieving complete elimination (below detection limit) of viable bacteria within 30 minutes-3 hours at 1X MBC, considerably faster than doxycycline. BEO retained its antibacterial efficacy following exposure to temperatures (37-100°C), digestive enzymes (α-amylase, pepsin and proteinase-K), physiological salts (NaCl and MgCl2) and pH (2-8), indicating excellent physico-chemical stability. Mechanistic studies showed extensive degradation of bacterial genomic and plasmid DNA with minimal extracellular nucleic acid leakage, suggesting membrane disruption accompanied by intracellular DNA damage as the principal antibacterial mechanism. Safety evaluation against Lactiplantibacillus plantarum MTCC2621 showed that lactobacilli cells remained viable even at the highest concentration of BEO tested, indicating its selective inhibitory activity against pathogenic bacteria. BEO at 10%(v/v) concentration also exhibited significantly higher antioxidant activity as compared to standard chemical antioxidants, with 50% inhibition (IC50) of DPPH radical scavenging at just 2µg/mL. In a chicken breast meat challenge study, treatment of MDR ESBL-EC inoculated-meat samples with BEO significantly (p≤0.05) reduced the bacterial load, limited increases in pH and lipid oxidation (TBARS values), and maintained desirable sensory quality attributes throughout 9 days of refrigerated storage (4±1℃) under aerobic packaging condition. Collectively, these findings demonstrated that BEO can be used as a promising natural antimicrobial, antioxidant, and food-preservative agent for controlling MDR ESBL-EC and improving food safety within the One Health framework. Keywords: Bamboo Essential Oil, Multidrug resistance, ESBL-producing E. coli, Antimicrobial, Antioxidant, Food safety, One Health.