Efficacy of Thai Plant Extracts for Antibacterial and Anti-Biofilm Activities against Pathogenic Bacteria.

Dennapa Saeloh,Monton Visutthi

doi:10.3390/antibiotics10121470

Dennapa Saeloh, Monton Visutthi

Open Access

https://doi.org/10.3390/antibiotics10121470

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Abstract

The emergence of drug-resistant bacteria has impacted the outcome of current therapeutics as a threat to global healthcare; novel medicines are urgently needed. Thirteen medicinal plants were collected in Northeastern Thailand, and their crude ethanolic extracts were evaluated for antibacterial activities against Staphylococcus aureus ATCC25923 and Escherichia coli ATCC25922 using the broth micro-dilution method. Piper betle leaf ethanolic extract showed optimal activity against both representative bacterial strains. Activity was also observed against clinical isolates of methicillin-resistant S. aureus (MRSA) and E. coli, with minimal inhibitory concentration (MIC) ranging from 0.31 mg/mL to 2.5 mg/mL and minimal bactericidal concentration (MBC) ranging from 0.62 mg/mL to 2.5 mg/mL. A time-kill study revealed that the extract activity was time- and dose-dependent, and also bactericidal on the tested bacteria. P. betle extract inhibited biofilm formation and promoted biofilm eradication in both S. aureus and E. coli. 4-Allyl-1,2-diacetoxybenzene and eugenol were identified as the most abundant compounds in the extract and may play major roles in the anti-bacterial and anti-biofilm activity. Results suggest that ethanolic P. betle leaf extract shows promise as an alternative method for the prevention of bacterial diseases.

Highlights

Drug-resistant bacteria are a serious global healthcare problem, leading to poor outcomes of current therapeutics
Thirteen ethanolic extracts from selected plants were tested for antibacterial activity against Gram-positive and Gram-negative bacteria by the broth microdilution method
The primary results showed that P. betle leaf extract inhibited the reference bacteria (Table 1), and this leaf extract was selected as a representative agent to evaluate antibacterial activity against 91 clinical bacterial isolates

Summary

Introduction

Drug-resistant bacteria are a serious global healthcare problem, leading to poor outcomes of current therapeutics. Microorganisms generate biofilms and form a community on the host surface to protect themselves from the environment. Biofilms are mostly found in medical, industrial, food processing and water distribution systems [1,2]. Biofilm-embedded bacteria are able to increase their defenses against antibiotics at up to a thousand-fold, compared to planktonic cells [3]. Most current antibiotics are effective against unattached bacteria, but the treatment of biofilm infections requires antibiotics at high concentrations, usually above peak serum levels. Therapeutics for latent and recurrent infections are less effective [4]. The elimination of bacteria within the biofilm requires degradation of the biofilm matrix or the discovery of antibiotics that can enter through the biofilm

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