Investigation on anti-pathogenic potential of Herboheal formulation and Phyllanthus emblica L. seed extract against selected human-pathogenic bacteria

Abstract

n context of the global threat of antimicrobial resistance (AMR) among pathogenic bacteria against conventional bactericidal antibiotics, investigation on complementary/ alternative approaches to manage bacterial infections is urgently warranted. Present study aimed at investigating the anti-pathogenic potential of Herboheal formulation (HF; a polyherbal formulation), and Phyllanthus emblica seed extract (PESE) against four different pathogenic bacteria viz. three antibiotic-resistant gram-negative bacteria Chromobacterium violaceum, Serratia marcescens, Pseudomonas aeruginosa (latter two are #CDC-listed), and one gram-positive bacterium Staphylococcus aureus. This study has found both the extracts to be effective broad-spectrum quorum modulators, as they could affect production of QS (quorum sensing)-regulated pigments and other virulence traits in gram-positive as well as gram-negative bacterial pathogens. PESE and HF were found to exert in vitro quorum-modulatory effect on these pathogens at ≥50 µg/mL and ≥0.025%v/v respectively. These extracts could curb the hemolytic activity of all the four test bacteria by 18-69%. Test formulations not only could inhibit (24-55%) biofilm formation, but also eradicated (18-63%) pre-formed biofilm effectively, and were also able to modulate bacterial antibiotic susceptibility and catalase activity (5-21%). Susceptibility of P. aeruginosa and S. aureus to lysis by human serum was enhanced under the influence of these extracts by 23-86%. Repeated exposure of both these notorious pathogens to PESE or HF did not induce resistance in them. In vivo assay demonstrated the ability of these extracts of attenuating (7-70%) bacterial virulence towards the model host C. elegans. Whole transcriptome analysis revealed certain genes associated with hemolysis, virulence, enzyme activity, transport, basic cellular processes (e.g. RNA metabolism), quorum sensing, and transcriptional regulators as the major targets of Herboheal in S. aureus. Both the extracts also showed notable prebiotic potential by promoting the growth (by 6-54%) of three probiotic strains- Lactobacillus plantarum, Enterococcus faecium, and Bifidobacterium bifidum. Some of the constituent phytochemicals of PESE were also assayed in their pure form for their possible anti pathogenic property. However, individual phytochemicals alone were not found to be as effective as the crude extract. This study validates the anti-infective potential of a folklore-based wound-healing formulation (Herboheal), and P. emblica seed extracts, indicated in texts of traditional medicine e.g. Ayurved; besides demonstrating therapeutic relevance of the ‘polyherbalism’ concept.