Inhibition of New Delhi Metallo-β-Lactamase 1 (NDM-1) Producing Escherichia coli IR-6 by Selected Plant Extracts and Their Synergistic Actions with Antibiotics.

Brinda Chandar,Sundar Poovitha,Ramasamy Mohankumar,Kaliappan Ilango,Madasamy Parani

doi:10.3389/fmicb.2017.01580

Brinda Chandar, Sundar Poovitha + Show 3 more

Open Access

https://doi.org/10.3389/fmicb.2017.01580

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Abstract

Improper use of antibiotics has led to a great concern in the development of pathogenic microbial resistance. New Delhi metallo-β-lactamase 1 (NDM-1) producing bacteria are resistant to most of the β-lactam antibiotics, and so far, no new compounds have been clinically tested against these bacteria. In this study, ethanol extracts from the leaves of 240 medicinal plant species were screened for antibacterial activity against an NDM-1 Escherichia coli strain. The extracts that showed antibacterial activity were then tested for minimum inhibitory concentrations (MICs) and zones of inhibition. The extract from Combretum albidum G. Don, Hibiscus acetosella Welw. ex Hiern, Hibiscus cannabinus L., Hibiscus furcatus Willd., Punica granatum L., and Tamarindus indica L. showed bactericidal activity between 5 and 15 mg/ml and the MIC was between 2.56 and 5.12 mg/ml. All six plant extracts inhibited activity of the NDM-1 enzyme in vitro, and the IC50 value ranged between 0.50 and 1.2 ng/μl. Disruption of bacterial cell wall integrity by the plant extracts was clearly visible with scanning electron microscopy. Increases in membrane permeability caused 79.4–89.7% bacterial cell deaths as investigated by fluorescence-activated cell sorting. All the plant extracts showed synergistic effects when combined with colistin [fractional inhibitory concentration (ΣFIC) = 0.125–0.375], meropenem (ΣFIC = 0.09–0.313), and tetracycline (ΣFIC = 0.125–0.313). Thus, the plant extracts can be fractionated for the identification of active compounds, which could be used as new antibacterial compounds for the development of drugs against NDM-1 E. coli in addition to their use in combination therapy.

Highlights

Extensive use of antibiotics in the past has led to the emergence of bacterial resistance among pathogenic microorganisms
The size of New Delhi metallo-β-lactamase 1 (NDM-1) gene amplified from plasmid DNA was 475 bp and that of the 16S rDNA amplified from genomic DNA was 1500 bp
Colistin was discontinued in the 1970s from clinical use due to its reported nephrotoxicity and neurotoxicity, but it re-emerged as a potent antibiotic to control infections due to NDM-1 bacteria

Summary

Introduction

Extensive use of antibiotics in the past has led to the emergence of bacterial resistance among pathogenic microorganisms. Β-Lactam antibiotics account for about 60% of all antibacterial agents used to treat the infections caused by Gram-negative bacteria (Livermore and Woodford, 2006). Active Plant Extracts against NDM-1 E. coli are some ways in which they acquire resistance. Bacteria counteract these antibiotics by acquiring the ability to produce β-lactamases, extended spectrum β-lactamases, AmpC enzymes, and metallo-β-lactamases (MBLs) (Carattoli, 2009). The recently discovered New Delhi metallo-β-lactamase 1 (NDM-1), which confers extensive antibiotic resistance against most of the currently available β-lactam antibiotics, is a global concern. It is necessary to explore the possibility of finding new and effective antibacterial compounds against NDM-1 bacteria

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