Prevalence, Persistence, and Diversity of and Species in Produce Packinghouses in Three U.S. States.

has emerged as a food safety concern for several produce commodities. Although contamination can occur throughout the supply chain, contamination from the packinghouse environment represents a particular challenge and has been linked to outbreaks and recalls. This study aimed to investigate the prevalence, persistence, and diversity of and other species of in produce packinghouses. A longitudinal study was performed in 11 packinghouses (whose commodities included microgreen, peach, apple, tomato, broccoli, cauliflower, and cucumber) in three U.S. states. In each packinghouse, 34 to 47 sites representing zones 2 to 4 were selected and swabbed. Packinghouses were visited four times over the packing season, and samples were tested for by following the U.S. Food and Drug Administration's methods. Presumptive -positive isolates were confirmed by PCR. Species and allelic type (AT) were identified by sequencing for up to eight isolates per sample. Among 1,588 samples tested, 50 (3.2%), 42 (2.7%), and 10 (0.6%) samples were positive for only, spp. (excluding ) only, and both and spp., respectively. Five species of ( and ) were identified, and was the most prevalent species. The 102 -positive samples yielded 128 representative isolates (i.e., defined as isolates from a given sample with a different AT). Approximately 21% (21 of 102) of the -positive samples contained two or more ATs. A high AT diversity (0.95 Simpson's diversity index) was observed among isolates. There were three cases of or spp. repeated isolation (site testing positive at least twice) based on AT data. Data from this study also support the importance of drain and moisture management, because were most prevalent in samples collected from drain, cold storage, and wet nonfood contact surface sites.