Phytochemical mixtures and NHPs as antimicrobials against antibiotic resistant Neisseria gonorrhoeae and other pathogens

Abstract

Phytochemicals and garlic extracts were evaluated for their potential as complementary treatments against Neisseria gonorrhoeae. The minimum inhibitory concentrations (MICs) of the phytochemicals silibinin and dillapiol, and a panel of garlic natural health products were determined against a panel of resistant and susceptible N. gonorrhoeae strains using agar and broth dilution methods and bacterial killing curves. Combinations of subinhibitory concentrations of silibinin or dillapiol with penicillin elicited a significant reduction in MICs of ∼50% and ∼25% of the tested strains respectively. Ternary combinations of silibinin, dillapiol and penicillin yielded a significant MIC reduction in 88% of the tested strains, including some strains whose penicillin MICs were reduced below the penicillin resistance breakpoint. The garlic extracts exhibited discrepancies in product composition and antimicrobial activity, with few products having comparable activity to fresh garlic. The activity of these phytochemicals against multiple N. gonorrhoeae resistance phenotypes makes them worthy of further investigation.