title: Prevalence, Level, and Types of Salmonella Isolated from North American In-Shell Pecans over Four Harvest Years.
abstract: In-shell pecan samples (500 g) were collected over four harvest seasons (2010 to 2014) from seven pecan shelling facilities located in five U.S. states. Four varieties of pecans were analyzed: Mexican Improved, Native Seedlings, Southern Improved, and Western Improved. Pecan samples (100 g) were sent to a third party laboratory for initial Salmonella screening. When a sample was positive for Salmonella, the pathogen level was determined by the most-probable-number (MPN) method (25, 2.5, and 0.25 g). Two sample preparation strategies were used for the MPN analysis, and both strategies were combined for the reported MPN values. Forty-four (0.95%) of 4,641 in-shell pecan samples were positive for Salmonella during initial screening; prevalence by year was 0.47 to 1.4%. Prevalence was not significantly different between varieties: Mexican Improved, 1.2%; Native/Seedling, 0.99%; Southern Improved, 0.97%; and Western Improved, 0.75%. Salmonella was not isolated from 31 of 44 samples upon retesting during MPN analysis (<0.47 MPN/100 g). When Salmonella was detected, the levels were 0.47 to 39 MPN/100 g, with a mean of 2.4 MPN/100 g. Thirty-one Salmonella serotypes were obtained from 42 Salmonella-positive pecan samples; Enteritidis was the most common (12% of samples) followed by Javiana (9%) and Braenderup (7%). All Salmonella Enteritidis isolates were phage type 8. Pulsed-field gel electrophoresis analysis (XbaI) revealed within-serotype diversity, indicating introduction of contamination from a variety of sources. Most (64%) of the isolates were resistant to streptomycin or tetracycline, and 13% were resistant to three or more antibiotics. Salmonella prevalence and level on in-shell pecans is comparable to that on other nuts.
authors.affiliation: Department of Food Science and Human Nutrition, Citrus Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, 700 Experiment Station Road, Lake Alfred, Florida 33850, USA.
authors.forename: Pardeepinder K
authors.initials: PK
authors.lastname: Brar
authors.affiliation: Department of Food Science and Technology, Agricultural Research and Extension Center, Virginia Polytechnic Institute and State University, 33446 Research Drive, Painter, Virginia 23420, USA.
authors.forename: Laura K
authors.initials: LK
authors.lastname: Strawn
authors.affiliation: Department of Food Science and Human Nutrition, Citrus Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, 700 Experiment Station Road, Lake Alfred, Florida 33850, USA.mddanyluk@ufl.edu.
authors.forename: Michelle D
authors.initials: MD
authors.lastname: Danyluk
mesh_terms: D031325:Carya / Q000382:microbiology*; D015169:Colony Count, Microbial; D016172:DNA Fingerprinting; D004269:DNA, Bacterial / Q000302:isolation & purification; D024901:Drug Resistance, Multiple, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D005506:Food Contamination; D005516:Food Microbiology; D012477:Salmonella enteritidis / Q000302:isolation & purification*; D012703:Serotyping; D014481:United States
chemical_list: D004269:DNA, Bacterial