Exploratory comparative screening of antibacterial activity of processed and unprocessed honeys against wild-type and drug-resistant bacterial strains

Abstract

Background: Antimicrobial resistance (AMR) is a growing global health challenge requiring exploration of alternative antimicrobial agents. Honey has documented antibacterial properties, but activity varies by composition, and data on locally available honeys against drug-resistant pathogens remain limited. Aim: To compare the in vitro antibacterial activity of selected processed and unprocessed honeys against reference and drug-resistant bacterial isolates. Setting: The study was conducted in Limpopo province, South Africa, using locally sourced honey products. Methods: A laboratory-based experimental study evaluated four honeys, two unprocessed (A, B) and two processed (C, D), against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Streptococcus pyogenes and selected drug-resistant isolates, including methicillin-resistant S. aureus (MRSA), extended-spectrum β-lactamase (ESBL)-producing E. coli, carbapenem-resistant P. aeruginosa and Acinetobacter baumannii. Minimum inhibitory concentrations (MICs) were determined by broth microdilution, with disk diffusion used as a supplementary qualitative method. Data were analysed descriptively. Results: Minimum inhibitory concentrations ranged from 3.13% to 25% volume/volume. Unprocessed B and Processed D showed lower MICs against several organisms. No inhibition zones were observed for reference P. aeruginosa or S. pyogenes. Processed D produced the largest inhibition zone against MRSA (8 mm). Higher MICs were observed for A. baumannii across the honey samples. Conclusion: Selected honeys demonstrated variable in vitro antibacterial activity against reference and drug-resistant isolates. However, the absence of appropriate controls and compositional characterisation limits mechanistic and clinical interpretation. Contribution: This exploratory study provides preliminary data on the antibacterial activity of locally available honeys and supports further investigation using appropriate controls, chemical profiling and clinically relevant models.