Chemical Composition and Antibacterial Activity of Essential Oils from the Algerian Endemic Origanum glandulosum Desf. against Multidrug-Resistant Uropathogenic E. coli Isolates.

Larbi Zakaria Nabti,Joice Guileine Nkuimi Wandjou,Farida Sahli,Filippo Maggi,Ahmed Olowo-Okere,Hocine Laouar

doi:10.3390/antibiotics9010029

Abstract

Antibiotics are becoming ineffective against resistant bacteria. The use of essential oils (EOs) may constitute an alternative solution to fight against multidrug-resistant bacteria. This study aims to determine the chemical composition of EOs from five populations of the endemic Algerian Origanum glandulosum Desf. and to investigate their potential antibacterial activity against multidrug-resistant uropathogenic E. coli strains. The EOs were obtained by hydrodistillation and their composition was investigated by gas chromatography/mass spectrometry (GC/MS). The antibacterial activity was evaluated by the disc diffusion method against eight E. coli strains (six uropathogenic resistant and two referenced susceptible strains). Minimum inhibitory and bactericidal concentrations (MIC/MBC) were obtained by the broth microdilution method. The main EO components were thymol (15.2–56.4%), carvacrol (2.8–59.6%), γ-terpinene (9.9–21.8%) and p-cymene (8.5–13.9%). The antibacterial tests showed that all the EOs were active against all the strains, including the multidrug-resistant strains. The EO from the Bordj location, which contained the highest amount of carvacrol (59.6%), showed the highest antibacterial activity (inhibition diameters from 12 to 24.5 mm at a dilution of 1/10). To our knowledge, this is the first description of the activity of O. glandulosum EOs against resistant uropathogenic strains. Our study suggests that O. glandulosum EO could be used in some clinical situations to treat or prevent infections (e.g., urinary tract infections) with multidrug-resistant strains.

Highlights

Urinary tract infections (UTIs) are ones of the main hospital- and community-acquired bacterial infections [1]
The aims of this study were: (i) to determine the chemical composition of Essential oils (EOs) extracted from five different populations of O. glandulosum growing in Algeria, and (ii) to investigate the potential antibacterial activity of these EOs against MDR-uropathogenic E. coli strains
Since our five EOs were rich in thymol and/or carvacrol, we suggest that the obtained antibacterial activities were related to the high concentration of these two constituents

Summary

Introduction

Urinary tract infections (UTIs) are ones of the main hospital- and community-acquired bacterial infections [1]. Escherichia coli, the microorganism that is the most frequent cause of UTIs, has become resistant to many available antibiotics, including third generation cephalosporins, carbapenems and colistin [1,2]. Infections caused by multidrug-resistant (MDR) bacteria have become a major healthcare problem worldwide [3,4]. Antibiotics 2020, 9, 29 as volatile oils, are one of the main natural bioactive substances extracted from plants, and have been used as alternative medicines, especially as antimicrobial agents [5]. The EOs obtained from the genus Origanum L. have attracted the attention of microbiologists due to their widespread use as natural food preserving agents [6]

Objectives

Results

Discussion

Conclusion