A strong inhibitory effect of heather honey, propolis and medicinal plant extracts on biofilm formation by pathogenic bacteria

Abstract

Introduction: P. aeruginosa and S. aureus are opportunistic pathogens that cause a wide range of infections. Their increasing resistance to antibiotics is a serious concern and making them susceptible to treatments is now more essential than ever. There is a need to discover new biofilm inhibitors to increase the susceptibility of these bacteria to antibiotics. Hypothesis and aims: To evaluate the antibiofilm activity of heather honey, propolis and medicinal plant extracts against P. aeruginosa and S. aureus. Methodology: Determination of optimum biofilm growth was carried out using a time-course assay over 24 h intervals, using P. aeruginosa PA14 and S. aureus NCTC 4135 strains. The inhibitory effects of all extracts were determined by biofilm inhibition assay in 24-well plates, with biofilms stained with crystal violet and de-stained with ethanol:acetone; OD were measured at 550 nm. Planktonic growth was measured at 600 nm and samples from the wells were streaked to determine bactericidal effects. Results: Heather honey extracts inhibited both P. aeruginosa and S. aureus by 68%. At 60 μg/mL, one of the propolis extracts promoted biofilm growth of both pathogens. Two other propolis extracts also promoted growth in P. aeruginosa but inhibited biofilm formation in S. aureus by 76.5% and 13.8%, respectively. Three plant extracts inhibited S. aureus biofilm by 7.5%, 10.2% and 87.6% and inhibited P. aeruginosa by −34.9%, 34.7% and 19.4%, respectively. Conclusion: All samples showed varying biofilm inhibition capabilities, but biofilm formation seemed to be more easily inhibited in S. aureus than in P. aeruginosa.

In vivo and in vitro inhibition effect of propolis on Klebsiella pneumoniae : A review

“…Billah [ 31 ] evaluated the antibiofilm activity of heather honey propolis and medicinal plant extracts against P. aeruginosa and S. aureus to determine the optimum biofilm growth with a 24 h time-course assay using P. aeruginosa PA14 and S. aureus NCTC 4135 strains. Two propolis extracts promoted P. aeruginosa growth but inhibited biofilm formation in S. aureus by 76.5% and 13.8%, respectively.…”

“…Two propolis extracts promoted P. aeruginosa growth but inhibited biofilm formation in S. aureus by 76.5% and 13.8%, respectively. The inhibition of biofilm formation by propolis was easier with S. aureus than with P. aeruginosa [ 31 ]. Saddiq and Danial [ 32 ] examined the antimicrobial, antioxidant, and probiotic activity of commercial Saudi Arabian propolis, performing antimicrobial activity tests on the pathogenic K. pneumoniae, P. aeruginosa, E. coli, Aspergillus niger, and Aspergillus flavus.…”