Inhibitory activity of monofloral and multifloral honeys against bacterial pathogens.
Joan J. Gallardo-Chacón, Montserrat Caselles, Maria Izquierdo and Núria Rius
Thirty one honey samples were evaluated for their ability to inhibit the growth of ten bacterial pathogens: Escherichia coli O157:H7; Salmonella enterica ser. Typhimurium; Shigella sonnei; Pseudomonas aeruginosa; Bacillus cereus; Listeria monocytogenes; Staphylococcus aureus 9144 and MRSA; Streptococcus mutans; and Enterococcus faecalis, using a well diffusion assay. All Gram-negative bacteria except P. aeruginosa were sensitive to all of the honey samples and also to artificial honey used as control at 25 % concentration. S. sonnei was the pathogen whose growth was most inhibited by honey. P. aeruginosa exhibited overgrowth of surrounding wells inoculated with five honey samples. Each Gram-positive pathogen and the different strains of S. aureus exhibited different sensitivities to honeys. The three honeys from Galicia (Spain) were the most active. E. coli O157:H7, S. sonnei, MRSA, S. mutans and E. faecalis were studied for specific inhibitory activity. E. coli O157:H7, S. sonnei and E. faecalis were inhibited by high sugar concentration. The inhibition of MRSA and S. mutans was caused by hydrogen peroxide generation. MRSA was also inhibited by two unprocessed honeys due to the presence of proteinaceous compounds. Such activity is potentially of importance in honey used as wound dressing and also as a preservative in minimally processed foods.