AUTHOR=Khan Muhammad Faraz , Tang Huaqiao , Lyles James T. , Pineau Rozenn , Mashwani Zia-ur-Rahman , Quave Cassandra L. 

TITLE=Antibacterial Properties of Medicinal Plants From Pakistan Against Multidrug-Resistant ESKAPE Pathogens

JOURNAL=Frontiers in Pharmacology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/pharmacology/articles/10.3389/fphar.2018.00815

DOI=10.3389/fphar.2018.00815

ISSN=1663-9812

ABSTRACT=<p>Local people in the Sudhnoti district of Pakistan share a rich practice of traditional medicine for the treatment of a variety of ailments. We selected nine plants from the Sudhnoti ethnopharmacological tradition used for the treatment of infectious and inflammatory disease. Our aim was to evaluate the <italic>in vitro</italic> anti-infective potential of extracts from these species against multidrug-resistant (MDR) ESKAPE (<italic>Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumanii, Pseudomonas aeruginosa</italic>, and <italic>Enterobacter</italic> species) pathogens. Plant specimens were collected in the Sudhnoti district of Pakistan and vouchers deposited in Pakistan and the USA. Dried bulk specimens were ground into a fine powder and extracted by aqueous decoction and maceration in ethanol. Extracts were assessed for growth inhibitory activity against ESKAPE pathogens and biofilm and quorum sensing activity was assessed in <italic>Staphylococcus aureus</italic>. Cytotoxicity to human cells was assessed via a lactate dehydrogenase assay of treated human keratinocytes (HaCaTs). Four ethanolic extracts (<italic>Zanthoxylum armatum, Adiantum capillus-venaris, Artemisia absinthium</italic>, and <italic>Martynia annua</italic>) inhibited the growth of MDR strains of ESKAPE pathogens (IC<sub>50</sub>: 256 μg mL<sup>−1</sup>). All extracts, with the exception of <italic>Pyrus pashia</italic> and <italic>M. annua</italic>, exhibited significant quorum quenching in a reporter strain for <italic>S. aureus agr</italic> I. The ethanolic extract of <italic>Z. armatum</italic> fruits (Extract 1290) inhibited quorum sensing (IC<sub>50</sub> 32–256 μg mL<sup>−1</sup>) in <italic>S. aureus</italic> reporter strains for <italic>agr</italic> I-III. The quorum quenching activity of extract 1290 was validated by detection of δ-toxin in the bacterial supernatant, with concentrations of 64–256 μg mL<sup>−1</sup> sufficient to yield a significant drop in δ-toxin production. None of the extracts inhibited <italic>S. aureus</italic> biofilm formation at sub-inhibitory concentrations for growth. All extracts were well tolerated by human keratinocytes (LD<sub>50</sub> ≥ 256 μg mL<sup>−1</sup>). Chemical analysis of extract 1290 by liquid chromatography-Fourier transform mass spectrometry (LC-FTMS) revealed the presence of 29 compounds, including eight with putative structural matches. In conclusion, five out of the nine selected anti-infective medicinal plants exhibited growth inhibitory activity against at least one MDR ESKAPE pathogen at concentrations not harmful to human keratinocytes. Furthermore, <italic>Z. armatum</italic> was identified as a source of quorum quenching natural products and further bioassay-guided fractionation of this species is merited.</p>