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Flies are a vector for spreading foodborne pathogens pertinent to fresh produce, such as Shiga toxigenic Escherichia coliand Salmonella; however, most studies focus on concentrated animal feeding operations, which do not reflect low-density animal farming practices that often adjoin fruit and vegetable acreage. In this study, we determined the prevalence of Salmonellain flies collected biweekly on an integrated animal and produce operation over two growing seasons. Eleven of 889 pooled samples tested positive for Salmonella. Flies from the Calliphoridae, Muscidae, Sarcophagidae, and Tachinidae families were associated with Salmonellacarriage, but fly family was not a significant factor for isolation of Salmonella(P= 0.303). Fly species were a significant factor (P= 0.026), with five Pentacricia aldrichiipools testing positive for Salmonella. With the exception of single specimen isolation, prevalence ranged from 2.2 to 15.2%. With the exception of the Tachinidae family, these results reflect a strong association of flies that are commonly associated with feces or are pests of animals. Trap location was not significantly associated with isolation of Salmonella-positive flies (P= 0.236). Overall, the population of flies was not as abundant as studies conducted with produce grown close to concentrated animal feeding operations, indicating a reduced risk of transmission; however, similar to these studies, fly families that are commonly isolated from fecal and decaying matter were most frequently associated with Salmonellaisolation. Further work is warranted to elucidate the foodborne pathogen transmission rates to produce and subsequent survival over time.

Listeria monocytogeneshas emerged as a food safety concern for several produce commodities. Although L. monocytogenescontamination 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 L. monocytogenesand other species of Listeriain 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 Listeriaby following the U.S. Food and Drug Administration's Bacteriological Analytical Manualmethods. Presumptive Listeria-positive isolates were confirmed by PCR. Species and allelic type (AT) were identified by sigBsequencing 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 L. monocytogenesonly, Listeriaspp. (excluding L. monocytogenes) only, and both L. monocytogenesand Listeriaspp., respectively. Five species of Listeria(L. monocytogenes, L. innocua, L. seeligeri, L. welshimeri,and L. marthii) were identified, and L. monocytogeneswas the most prevalent species. The 102 Listeria-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 Listeria-positive samples contained two or more ATs. A high AT diversity (0.95 Simpson's diversity index) was observed among Listeriaisolates. There were three cases of L. monocytogenesor Listeriaspp. 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 Listeriawere most prevalent in samples collected from drain, cold storage, and wet nonfood contact surface sites.

•Contact time and sanitizer type influenced STEC and E. coliTVS 353 reductions.•STEC panel was more sensitive to chlorine and peracetic acid than E. coliTVS 353.•All Cl treatments achieved ≥3 log10CFU/100 mL reduction in STEC and E. coliTVS 353.•E. coliTVS 353 is a good surrogate candidate for in-field experiment validations.•Water quality management is important to maintain residual sanitizer concentrations.