Food Protection Trends - September/October 2016 - 357

PEER-REVIEWED ARTICLE Dongryeoul Bae,1 Ronald D. Smiley,2 Ezat H. Mezal3 and Ashraf A. Khan1* Food Protection Trends, Vol 36, No. 5, p.357-361 Copyright© 2016, International Association for Food Protection 6200 Aurora Ave., Suite 200W, Des Moines, IA 50322-2864 Division of Microbiology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR 72079, USA 1* Arkansas Regional Laboratory, Office of Regulatory Affairs, U.S. Food and Drug Administration, Jefferson, AR 72079, USA 2 Dept. of Biology, University of Thi-Qar, Thi-Qar, Iraq 3 Food Products and Processing Facilities Linked to Recent Outbreaks of Listeriosis in the US Frozen Vegetables (2016, WA) Cheeses (2013, WI) Raw Milk (2016, PA) Soy Products (2014, IL) Packaged Salads Dairy Products (2016, OH) (2014, DE) Caramel Apples (2014 - 2015, CA) Caramel Apples (2014 - 2015, MO) Ice Cream (2015, OK) Soft Cheese (2015, CA) Ice Cream (2015, AL) Ice Cream Product (2015, TX) Soft Cheese (2014, FL) Data source: Centers for Disease Control and Prevention www.cdc.gov/listeria/outbreaks/index,html Characterization and Antimicrobial Resistance of Listeria monocytogenes Isolated from Food-related Environments ABSTRACT The purpose of this study was to determine the diversity and antimicrobial resistance of Listeria monocytogenes strains isolated from food-related environments in the United States. Nineteen unrelated strains of L. monocytogenes were recovered from approximately 1300 food and food processing environmental samples collected from 2007 to 2011 as part of the U.S. Food and Drug Administration pathogen surveillance program. The L. monocytogenes environmental isolates were characterized by serotyping, subtyping, and identification of antimicrobial resistance determinants. The serovars of L. monocytogenes were 1/2a, 4b, and 1/2b. PFGE using AscI digested total DNA showed genetic diversity; there were 10 PFGE pulse-types and 5 PFGE groups. All strains except one strain were susceptible to ampicillin, erythromycin, vancomycin, ciprofloxacin, and chloramphenicol but resistant to extended-spectrum cephalosporins (ESC). The environmental strains were predominantly resistant to streptomycin and tetracycline. No strain was resistant to 3 or more antimicrobial classes. All tetracycline-resistant strains were serotype 1/2a, and only tetM was amplified from the chromosomal DNA. This study, which reports the genetic diversity and antimicrobial resistance of foodborne L. monocytogenes, may be useful in food safety control programs to reduce the risk of transmission of L. monocytogenes to food products. INTRODUCTION Listeria monocytogenes, a Gram-positive, facultatively intracellular foodborne bacterial pathogen that causes human listeriosis (6, 13), is widely distributed in the natural environment and foods. L. monocytogenes has been recognized as a major human foodborne pathogen ever since a large Listeria outbreak occurred in 1983 in the United States (U.S.) from improperly pasteurized milk (13). The hospitalization (91.0%) and mortality (19.5%) rates due to listeriosis are estimated to be the highest among those caused by foodborne pathogens in the U.S. *Corresponding author: Phone: +1 870.543.7601; Fax: +1 870.543.7307; E-mail: Ashraf.Khan@fda.hhs.gov September/October Food Protection Trends 357 http://www.foodprotection.org/files/food-protection-trends/sep-oct-16-bae.pdf http://www.cdc.gov/listeria/outbreaks/index.html

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