Browsing by Author "Hamilton, Alexis M."

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    Cyberbiosecurity Importance in Relation to Small Fermentation Businesses and How to Integrate it into Known Hazard Planning Tools
    Knapp, Jordan; Strawn, Laura K.; Wiersema, Brian D.; Eifert, Joseph D.; Hamilton, Alexis M. (Virginia Tech, 2024-08-07)
    Cyberbiosecurity threats are on the rise in many various industries (Drape et al., 2021). With attacks on water treatment plants, medical facilities and more, awareness for what cyberbiosecurity is, what it looks like, and how to implement countermeasures into known hazard planning tools is dire. This project set out to address these issues in the context of small fermentation businesses. A survey was conducted but, due to low response rate, there was no statistical nor quantitative analysis performed on the survey results. The information gleaned from the survey was used to better guide how a factsheet would be created and used to gauge, what the fermentation community in North Carolina and Virginia was aware of in relation to food safety, the Food Safety and Modernization Act, and cyberbiosecurity. A factsheet was designed to guide small fermentation businesses on how to identify cyberbiosecurity is, what hazards exist, how to implement control measures into known hazard planning tools, and what methods exist to better protect their businesses.
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    Effect of pesticide application on Salmonella survival on inoculated tomato leaves
    Gu, Ganyu; Murphy, Claire M.; Hamilton, Alexis M.; Zheng, Jie; Nou, Xiangwu; Rideout, Steven L.; Strawn, Laura K. (Wiley, 2023-02)
    Outbreaks of Salmonellosis have been traced to contaminated tomato. The produce production environment poses a risk for Salmonella contamination; however, little is known about the effects of pest management practices on Salmonella during production. The study objective was to evaluate pesticide application on the inactivation of Salmonella on tomato leaves. Thirty greenhouse-grown tomato plants were inoculated with S. enterica serovars Newport or Typhimurium. Inoculation was performed by dipping tomato leaves in an 8-log CFU/mL Salmonella suspension with 0.025% (vol/vol) Silwet L-77 surfactant for 30 s, for a starting concentration of 6–7 log CFU/mL. Plants were treated with one of four pesticides, each with a different mode of action [acibenzolar- S-methyl, copper-hydroxide, peroxyacetic acid (PAA), and streptomycin]. Pesticides were applied at manufacturers' labeled rate for plant disease management with water as a control treatment. Salmonella was enumerated at 0.125 (3 h), 2, 6, and 9 days post-inoculation (dpi), and counts log-transformed. Growth of Salmonella was not observed. At 2 dpi, PAA and streptomycin significantly reduced surface Salmonella concentrations of inoculated tomato leaves (0.7 and 0.6-log CFU/g, respectively; p ≤ 0.05), while significant Salmonella log reduction occurred in the ground tomato leaves after copper hydroxide treatment (0.8-log CFU/g; p ≤ 0.05), compared to the control. No significant differences in Salmonella populations on tomato leaf surface and in ground leaves were observed from 2 to 9 dpi, regardless of pesticide application. These findings suggest single in-field pesticide applications may not be an effective mitigation strategy in limiting potential Salmonella contamination. Future research, including multiple in-field pesticide applications, or pesticide use in combination with other mitigation strategies, may offer intriguing management practices to limit possible preharvest contamination.
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    Evaluating Risks and Mitigation Measures for Foodborne Pathogens on Harvest Bags
    Ayuk Etaka, Cyril Nsom (Virginia Tech, 2024-06-07)
    Tree fruit growers need information on pathogen dynamics following harvest bags contamination to determine effective sanitation interventions for decontaminating these surfaces. Therefore, the objectives of this research were (i) to determine the survival of generic E. coli, Salmonella, and L. monocytogenes on different harvest bag materials (ii) to quantify the transfer of generic E. coli, Salmonella, and L. monocytogenes from different harvest bag materials to fresh unwaxed apples and (iii) to determine the efficacy of different sanitizers for decontaminating different harvest bag materials. For Obj. 1, harvest bag materials were inoculated with rifampicin-resistant (80ppm; R) E. coli (TVS353) or Salmonella strain cocktail or L. monocytogenes strain cocktail. All surfaces were air-dried and held at 22 °C and either 30 or 80% relative humidity for 90 d (E. coli), or at 22 °C and 55% relative humidity (RH) for 21 d (L. monocytogenes and Salmonella). For Obj. 2, harvest bag materials were inoculated with E. coli (TVS353) or Salmonella strain cocktail or L. monocytogenes strain cocktail and air dried as previously mentioned. For E. coli trials, bacterial transfer to unwaxed 'Red Delicious' apples was assessed for 2 inoculum dry times (1 or 4 h), 2 contact times (5 or 25 minutes), and 2 pressure scenarios (0.0 or 0.1kg/cm2). For Salmonella or L. monocytogenes trials, transfer was assessed for 1 inoculum dry time (1 h), and 1 contact time (5 minutes). For Obj. 3, coupons were inoculated with L. monocytogenes or Salmonella cocktails and were air-dried. Following inoculation, coupons were exposed to different sanitizer treatments: chlorine, peroxyacetic acid (PAA), isopropyl alcohol with quaternary ammonium compounds (IPAQuats), steam, and water. Regression models were fitted, and Tukey's post hoc test was performed at P<0.05. E. coli exhibited survival for extended durations at 30 % than at 80% RH. In addition, E. coli survived at higher concentrations on canvas surfaces than on cordura and nylon surfaces. Generally, E. coli survived for more than 21 d across all surfaces and exhibited a triphasic die-off pattern. Similarly, L. monocytogenes and Salmonella exhibited die-off in phases with an initial rapid die-off followed by more gradual die-off rates up to 21 d. Canvas materials also promoted better L. monocytogenes and Salmonella survival than cordura surfaces. Contact time did not significantly impact the transfer of E. coli from harvest bag surfaces to apples (P=0.55). However, pressure, inoculum dry time and material type significantly impacted the transfer of E. coli to 'Red Delicious' apples (P≤0.03). The transfer rates of Salmonella did not differ between canvas and cordura surfaces (P=0.46). However, cordura transferred L. monocytogenes at significantly higher rates than canvas surfaces (P<0.001). Of the sanitizer treatments that were used on L. monocytogenes or Salmonella inoculated surfaces, IPAQuats was the most effective achieving over 4.5 log CFU/coupon reduction on both canvas and cordura surfaces. Our studies demonstrated that bacteria could survive for over 21 d under different conditions and could transfer from contaminated harvest bag surfaces to apples underlining the importance of cleaning and sanitizing harvest bags with sanitizers like IPAQuats.
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    Evaluating the Cross-Contamination Risks of Salmonella and Generic Escherichia coli on Agricultural Ground Covers in Produce Pre-Harvest Production
    Rosenbaum, Alyssa Anne (Virginia Tech, 2024-05-16)
    The US Food and Drug Administration Food Safety Modernization Act (FSMA) Produce Safety Rule (PSR) prohibits the harvest of dropped fruits and vegetables due to potential microbial contamination. Under the FSMA PSR dropped produce includes (i) produce that has detached from the parent plant and unintentionally contacts the ground and (ii) produce that is attached to the parent plant and unintentionally contacts the ground. Due to the benefits of plant growth and pest management, agricultural ground covers are a common horticultural practice implemented in the fresh produce production environment and produce may come into contact with these ground covers. Thus, this thesis aims to (i) quantify the survival of bacteria on different agricultural ground cover types and in different production environments and (ii) evaluate the cross-contamination risk of mulch to fresh produce from different drop heights and contact times. A seven-strain Salmonella cocktail was spot inoculated on coupons of biodegradable mulch, landscape fabric, and plastic mulch, and held in a growth chamber (23°C, 55% RH). At 0, 0.06, 0.17, 1, 2, 3, 5, 7, 30, 60, 90, and 140 days post-inoculation (dpi), coupons were enumerated for Salmonella. Coupons of plastic mulch were also spot inoculated with a green-fluorescent protein-tagged generic Escherichia coli and held in a growth chamber, greenhouse, and field environment for enumeration at 0, 0.06, 0.17, 0.41, 1, 2, 3, 5, and 7 dpi. Fresh cucumber, jalapeño, and tomato were dropped from 0, 1, 2, 4, and 6 ft using height-modified PVC (polyvinyl chloride) pipes onto generic E. coli inoculated plastic mulch, as well as tomato onto inoculated biodegradable mulch. Produce samples were enumerated after 3 s of mulch contact. Fresh cucumber, jalapeño, and tomato were also grown in contact with generic E. coli inoculated plastic mulch for 0, 1, 3, 5, and 7 days post-placement in the field. Salmonella survived on all ground covers for up to 140 dpi in the growth chamber. From 0 to 30 dpi, biodegradable mulch had the lowest Salmonella reduction, followed by landscape fabric and then plastic mulch (P < 0.05). No significant differences in ground cover type and Salmonella reduction were observed at 90 dpi (P > 0.05). Plastic mulch had the highest reduction of generic E. coli in the field followed by the greenhouse and growth chamber over 7 dpi (P < 0.05) with field and greenhouse coupons achieving approximately a 6-log reduction by 0.17 and 7 dpi, respectively. Ground cover type and environment impacted bacterial survival and highlighted the importance of growing location in risk management. Cucumber and tomato samples dropped from 4 (33%; 17%) and 6 (100%; 43%) ft were damaged, respectively. In general, generic E. coli transferred to the tested commodities regardless of drop height or contact time. These findings support that dropped produce should not be harvested due to potential damage and when surfaces were contaminated, transfer was likely to occur. Similarly, if surfaces were contaminated, regardless of contact time (0, 1, 3, 5, and 7 d), transfer was likely to occur indicating cross-contamination poses a food safety risk despite unintentional or intentional ground contact. Food safety efforts should focus on minimizing visible contamination, as outlined in the FSMA PSR, that may contaminate fresh produce in the production environment. Growing produce in contact with the ground alone may not be the sole factor in the contamination of fresh produce, as a contamination event is needed.
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    Food Manufacturing Environmental Air Quality Monitoring Programs: A Literature Review and Best Practice Recommendations
    Murphy, Benjamin (Virginia Tech, 2024-04-29)
    Poor air quality in food production environments can pose food safety and quality risks if not properly monitored and managed. With little regulatory guidance, it is up to manufacturers and processors to define if air will be tested, organisms to test for, how sampling will be performed and how often. There is a variety of testing equipment and methods available, and it is difficult to find an unbiased guide to help set up a new program or improve current air quality monitoring practices. This literature review investigated the availability of easy to understand guidance materials and sought to create unbiased guidance to food industry professionals seeking to understand the key components of microbiological air quality monitoring programs and some of the options currently available. Relevant research is presented to help readers understand why it is important to monitor microbiological air quality, testing equipment available, organisms to monitor for, sampling location considerations, budget and staffing considerations and more. Furthermore, the project referenced throughout this paper provides additional insight into how these best practices may be applied as food safety and quality professionals seek to create or improve the microbiological air quality portion of an environmental monitoring plan.