Antibacterial Activity of Epigallocatechin Gallate Against Helicobacter Pylori: Synergistic Effect with Plaunotol

Recent advances to combat ESKAPE pathogens with special reference to essential oils

Biofilm-associated bacteria, especially ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.), are a serious challenge worldwide. Due to the lack of discovery of novel antibiotics, in the past two decades, it has become necessary to search for new antibiotics or to study synergy with the existing antibiotics so as to counter life-threatening infections. Nature-derived compounds/based products are more efficient than the chemically synthesized ones with less resistance and lower side effects. In this descriptive review, we discuss the most promising therapeutics for the treatment of ESKAPE-related biofilms. The first aspect includes different types of natural agents [botanical drugs, essential oils (EOs), antimicrobial peptides, bacteriophages, and endolysins] effective against ESKAPE pathogens. The second part of the review deals with special references to EOs/essential oil components (EOCs) (with some exclusive examples), mode of action (via interfering in the quorum-sensing pathways, disruption of biofilm and their inhibitory concentrations, expression of genes that are involved, other virulence factors), existing in literature so far. Moreover, different essential oils and their major constituents were critically discussed using in vivo models to target ESKAPE pathogens along with the studies involving existing antibiotics.

In vitro activity of curcumin in combination with epigallocatechin gallate (EGCG) versus multidrug-resistant Acinetobacter baumannii

BACKGROUND

Acinetobacter baumannii is an opportunistic human pathogen often associated with life-threatening infections in the immunocompromised and the critically ill. Strains are often multidrug-resistant (MDR) and due to the lack of new synthetic antimicrobials in development for treatment, attention is increasingly focused on natural compounds either as stand-alone or adjunctive agents. Curcumin (CCM) is a natural polyphenol found in turmeric and isolated from the plant, Curcuma longa. Curcumin has been found to possess many biological properties, including antibacterial activity. In this study the antimicrobial activity of CCM and synergistic effects with epigallocatechin gallate (EGCG) against multidrug-resistant strains of A. baumannii were investigated and assessed via checkerboard and time-kill assays.

RESULTS

The MIC of CCM was >256 μg/mL against all strains of A. baumannii whilst those for EGCG ranged from 128-1024 μg/mL. In checkerboard studies synergy was observed against 5/9 isolates, with an additive effect noted in the remaining 4. The addition of EGCG reduced the MIC of CCM by 3- to 7-fold, with the greatest interaction resulting in a CCM MIC of 4 μg/mL. Time-kill curves indicated that a CCM-EGCG (1:8 and 1:4) combination was bactericidal with a 4 to 5-log reduction in viable counts after 24 h compared to the most effective polyphenol alone.

CONCLUSIONS

This study demonstrates that despite little antibacterial activity alone, CCM activity is greatly enhanced in the presence of EGCG resulting in antibacterial activity against MDR A. baumannii. The combination may have a potential use in medicine as a topical agent to prevent or treat A. baumannii infections.