Evaluation of antibacterial activities of two types of local Jordanian honey with Manuka honey: A comparative study

Honey is one of the oldest traditional medicines that has been highly reputed and widely used for the treatment of several human diseases for thousands of years. The purpose of this study was to: (i) evaluate and compare the antibacterial and antibiofilm activities of Shawkiat and Rabiee honeys with those of Manuka honey against Escherichia coli and Staphylococcus aureus; (ii) assess the anti-virulence potential of these honeys, by examining their impacts on the expression of five selected genes in E. coli and seven genes in S. aureus that have been previously shown to be involved in the microcolony, biofilm and virulence in the test organism. The antibacterial, antibiofilm and anti-virulence activities of these honeys against both bacteria were investigated by agar well diffusion, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), growth curve, time-kill curve, microtiter plate and reverse transcription-quantitative real time polymerase chain reaction (RT-qPCR). The susceptibility tests showed promising antibacterial activities of Shawkiat and Rabiee honeys compared with Manuka honey against E. coli and S. aureus. The results showed that Manuka honey possessed the lowest MIC value against both bacteria with 20% (w/v) MIC and MBC of 25% (w/v). Slightly higher MIC values were shown by Shawkiat and Rabiee honeys against both bacteria with 25% (w/v) MIC and 50% (w/v) MBC values compared with Manuka honey. Growth curves demonstrated no growth of the two bacteria after treatment with MIC of all the tested honeys. Shawkiat and Rabiee honeys showed that both bacteria lost viability comparably with Manuka honey. The lowest concentration of Shawkiat and Rabiee honeys was able to inhibit and eradicate the biofilm of both bacteria compared with Manuka honey. The qPCR analysis showed that the expression of all the selected genes in both bacteria after treatment with all the tested honeys was downregulated and shared a similar overall pattern of gene expression, with a trend toward reduced expression of the virulence genes of interest. The results of this study indicate that Jordanian honeys possess antibacterial, antibiofilm and anti-virulence activities comparably with Manuka honey. This study revealed that Jordanian honey compared with Manuka honey inhibits E. coli and S. aureus planktonic cells and biofilm through the downregulation of genes required for growth, biofilm formation and motility.