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Access Type

WSU Access

Date of Award

January 2020

Degree Type

Thesis

Degree Name

M.S.

Department

Nutrition and Food Science

First Advisor

Dr. Yifan Zhang

Abstract

ABSTRACT

ISOLATION AND CHARACTERIZATION OF LISTERIA SPECIES FROM LOCALLY- GROWN FRESH PRODUCE

by

AMRITA SUBRAMANYA SWAMY

May 2020

Advisor: Dr. Yifan Zhang

Major: Nutrition and Food Science

Degree: Master of Science

Urban farming has been growing by more than 30% in the United States in the past 30 years. It has been estimated that urban agriculture can meet 15- 20% of global food demand; however, there is limited data available on microbial safety on the Listeria contamination in locally- grown fresh produce. The objective of the present study was to examine the prevalence and distribution of Listeria species and their ability to form biofilms at different temperatures. A total of 109 samples of leafy (86) and root (23) vegetables were pooled, followed by Listeria isolation and characterization, and biofilm determination. Clonal relatedness among bacteria was determined using PFGE. Common species such as L. innocua, L. welshimeri, and L. monocytogenes were recovered from fresh produce. Five L. monocytogenes isolates including P 52.1b (potato, 1/2a), P 43.1a (Radish, 4b), and three isolates of 4b from romaine lettuce (WV 11 a, WV 11 b and WV 11 c) were chosen for the determination of biofilm formation. Overall, biofilm formation was found to be high in all isolates except forWV11a that was a weak to moderate biofilm former. This study suggests that presence of Listeria species, including L. monocytogenes, in locally- grown fresh produce may pose public health concern to local consumers.

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