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      Antimicrobial Properties and Mechanism of Action of Some Plant Extracts Against Food Pathogens and Spoilage Microorganisms


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          This work aims to evaluate the antimicrobial potential of ethanolic and water extracts of roselle ( Hibiscus sabdariffa), rosemary ( Rosmarinus officinalis), clove ( Syzygium aromaticum), and thyme ( Thymus vulgaris) on some food pathogens and spoilage microorganisms. Agar well diffusion method has been used to determine the antimicrobial activities and minimum inhibitory concentrations (MIC) of different plant extracts against Gram-positive bacteria ( Bacillus cereus, Staphylococcus aureus), Gram-negative bacteria ( Escherichia coli, Salmonella enteritidis, Vibrio parahaemolyticus, and Pseudomonas aeruginosa), and one fungus ( Candida albicans). The extracts exhibited both antibacterial and antifungal activities against tested microorganisms. Ethanolic roselle extract showed significant antibacterial activity ( P < 0.05) against all tested bacterial strains, while no inhibitory effect on Candida albicans (CA) was observed. Only the ethanolic extracts of clove and thyme showed antifungal effects against CA with inhibition zones ranging from 25.2 ± 1.4 to 15.8 ± 1.2 mm, respectively. Bacillus cereus (BC) appears to be the most sensitive strain to the aqueous extract of clove with a MIC of 0.315%. To enhance our understanding of antimicrobial activity mechanism of plant extracts, the changes in internal pH (pH int), and membrane potential were measured in Staphylococcus aureus (SA) and Escherichia coli (EC) cells after exposure to the plant extracts. The results indicated that the plant extracts significantly affected the cell membrane of Gram-positive and Gram-negative bacteria, as demonstrated by the decline in pH int as well as cell membrane hyperpolarization. In conclusion, plant extracts are of great value as natural antimicrobials and can use safely as food preservatives.

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          Natural products as antimicrobial agents

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            Ultrasound: A clean, green extraction technology

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              Antimicrobial activity of some plant extracts against bacterial strains causing food poisoning diseases

              Prevention of food spoilage and food poisoning pathogens is usually achieved by use of chemical preservatives which have negative impacts including: human health hazards of the chemical applications, chemical residues in food & feed chains and acquisition of microbial resistance to the used chemicals. Because of such concerns, the necessity to find a potentially effective, healthy safer and natural alternative preservatives is increased. Within these texts, Plant extracts have been used to control food poisoning diseases and preserve foodstuff. Antimicrobial activity of five plant extracts were investigated against Bacillus cereus, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Salmonella typhi using agar disc diffusion technique. Ethanolic extracts of Punica granatum, Syzygium aromaticum, Zingiber officinales and Thymus vulgaris were potentially effective with variable efficiency against the tested bacterial strains at concentration of 10 mg/ml while extract of Cuminum cyminum was only effective against S. aureus respectively. P. granatum and S. aromaticum ethanolic extracts were the most effective plant extracts and showed bacteriostatic and bactericidal activities against the highly susceptible strains of food borne pathogenic bacteria (S. aureus and P. aeruginosa) with MIC's ranged from 2.5 to 5.0 mg/ml and MBC of 5.0 and 10 mg/ml except P. aeruginosa which was less sensitive and its MBC reached to 12.5 mg/ml of S. aromaticum respectively. These plant extracts which proved to be potentially effective can be used as natural alternative preventives to control food poisoning diseases and preserve food stuff avoiding healthy hazards of chemically antimicrobial agent applications.

                Author and article information

                Front Microbiol
                Front Microbiol
                Front. Microbiol.
                Frontiers in Microbiology
                Frontiers Media S.A.
                24 July 2018
                : 9
                : 1639
                [1] 1College of Food Science and Pharmaceutics, Zhejiang Ocean University , Zhoushan, China
                [2] 2Department of Food Science and Technology, College of Agricultural Science and Fisheries Technology, University of Dar es Salaam , Dar es Salaam, Tanzania
                [3] 3Zhoushan Institute of Food and Drug Inspection , Zhoushan, China
                [4] 4Faculty of Environmental Agricultural Science, Arish University , North Sinai, Egypt
                Author notes

                Edited by: Fatih Ozogul, Çukurova University, Turkey

                Reviewed by: Abderrahmane Houicher, University of Laghouat, Algeria; Mehmet Tolga Dincer, Ege University, Turkey

                *Correspondence: Meiling Chen, meilingchen@ 123456zjou.edu.cn ; Shaimaa R. Hatab, shaimaa_hatab@ 123456hotmail.com

                These authors have contributed equally to this work.

                This article was submitted to Food Microbiology, a section of the journal Frontiers in Microbiology

                Copyright © 2018 Gonelimali, Lin, Miao, Xuan, Charles, Chen and Hatab.

                This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

                : 25 May 2018
                : 02 July 2018
                Page count
                Figures: 3, Tables: 3, Equations: 1, References: 52, Pages: 9, Words: 0
                Funded by: National Natural Science Foundation of China 10.13039/501100001809
                Award ID: NSFC 31750110471
                Award ID: NSFC 3171101115
                Original Research

                Microbiology & Virology
                plant extract,ultrasound-assisted extraction,antimicrobial properties,internal ph (phint),membrane potential,spoilage,pathogenic microorganism


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