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 ofShawkiat and Rabiee honeys with those ofManuka honey against Escherichia coli and Staphylococcus aureus; (ii)assess the anti-virulence potential ofthese honeys, byexamining their impacts onthe expression offive selected genes inE.coli and seven genes inS.aureus that have been previously shown tobeinvolved inthe microcolony, biofilm and virulence inthe test organism. The antibacterial, antibiofilm and anti-virulence activities ofthese honeys against both bacteria were investigated byagar 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 ofShawkiat 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 of25% (w/v). Slightly higher MIC values were shown byShawkiat and Rabiee honeys against both bacteria with 25% (w/v) MIC and 50% (w/v) MBC values compared with Manuka honey. Growth curves demonstrated nogrowth ofthe two bacteria after treatment with MIC ofall the tested honeys. Shawkiat and Rabiee honeys showed that both bacteria lost viability comparably with Manuka honey. The lowest concentration ofShawkiat and Rabiee honeys was able toinhibit and eradicate the biofilm ofboth bacteria compared with Manuka honey. The qPCR analysis showed that the expression ofall the selected genes inboth bacteria after treatment with all the tested honeys was downregulated and shared asimilar overall pattern ofgene expression, with atrend toward reduced expression ofthe virulence genes ofinterest. The results ofthis 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.