Access Type

Open Access Thesis

Date of Award

January 2014

Degree Type

Thesis

Degree Name

M.S.

Department

Nutrition and Food Science

First Advisor

Yifan Zhang

Abstract

ABSTRACT

SCREENING OF NATURAL ANTIMICROBIAL AGENTS AND ANTIMICROBIAL - RESISTANT BACTERIA USING A SOLERIS SYSTEM

by

MINGYANG HUANG

May 2014

Advisor: Dr. Yifan Zhang

Major: Food Science and Nutrition

Degree: Master of Science

Traditional broth micro-dilution method is a common assay of measuring Minimum Inhibitory Concentration (MIC) to determine the antimicrobial activity of an antimicrobial agent. However, this method is generally time-consuming and labor intensive. Alternatively, an automated optical method using the Soleris system was applied in this study. The system was compared to the traditional broth micro-dilution 96-well assay to test the antimicrobial activity of 11 essential oils and 2 plant-derived compounds against Escherichia coli and Staphylococcus aureus. We also used the system to differentiate antimicrobial-resistant and -susceptible bacteria based on their antimicrobial resistance phenotypes. MIC values of cefoxitin against 5 strains of methicillin-resistant S. aureus (MRSA) and 8 strains of methicillin-susceptible S. aureus (MSSA) were tested. MIC values were also determined on cefoxitin, ampicilin and tetracycline against 11 ß-lactam-resistant E. coli and 3 susceptible E. coli. Most of the selected essential oils revealed strong antimicrobial effects against the tested microorganisms. Cinnamon oil and carvacrol compound were found to be more active against the test strains than any other selected antimicrobial agents. MICs obtained by Soleris system were comparable to those determined by standard micro-dilution method with respect to susceptibility testing of antimicrobial agents. The advantage of the Soleris system is its time efficiency and ease to perform. It provides a rapid and cost-efficient alternative for screening antimicrobial agents and antimicrobial-resistant bacteria.

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