Date of Graduation

8-2017

Document Type

Thesis

Degree Name

Master of Science in Cell & Molecular Biology (MS)

Degree Level

Graduate

Department

Cell & Molecular Biology

Advisor/Mentor

Gibson, Kristen E.

Committee Member

Barabote, Ravi D.

Second Committee Member

Ricke, Steven C.

Keywords

Fomites; Nonporous; Norovirus; Persistence; Swab

Abstract

Human enteric viruses such as human norovirus (hNoV) and Aichivirus A (AiV) are common foodborne viruses with hNoVs being identified as the leading causative agent of foodborne illnesses in the U.S. Moreover, hNoVs have been identified as the leading cause of nonbacterial acute gastroenteritis in the U.S. and worldwide. Fomite surface contamination is a major transmission route for enteric viruses. The application of an optimized virus recovery method from fomites is essential for better understanding of virus persistence under varying environmental conditions (EC). This study aimed to optimize a surface sampling method for virus recovery from nonporous food contact surfaces (FCS) for further application in environmental persistence studies under varying temperature and relative humidity (RH) combinations. Initially, feline calicivirus (FCV), hNoVs (GI.1; GII.17), AiV, and Tulane virus were selected for FCS sampling optimization. FCS selected for analysis included plastic chopping board, acrylic-based solid surface, and stainless steel. Sampling methods selected for evaluation included 3 implements (cell scraper, macrofoam swab, repeated pipetting) and 2 eluents (1×Phophaste buffered saline solution (PBS), 1×PBS+0.1%Tween80 (PBST; 1:1 v/v)). The repeated pipetting method with PBST eluent was selected for persistence studies though no significant differences were observed compared to other methods. Overall, mean recovery efficiencies using repeated pipetting with PBST ranged from 2.0% ± 0.6% to 82.36% ± 38.6% depending on virus and FCS type. For persistence studies, temperature (22°C, 15°C, 6°C) and RH (60%, 90%) combinations appropriate to food processing and storage were chosen for evaluation. AiV was stable on all FCS with about a 3 log10 titer reduction for 22°C/60% RH and 15°C/60% RH and about a 1 log10 titer reduction for 15°C/90% RH and 6°C/90% RH over 14d. Generally, higher RH (90%) displayed more stability for GI.1 and AiV over time than lower RH (60%), which is consistent with previous studies. However, lower temperatures may not be a major influencing factor of GI.1 and AiV persistence, which differed from previous studies. Furthermore, the impact of surface type was inconsistent which is similar to the variability seen across studies. This is the first study to demonstrate AiV persistence on nonporous FCS under varying EC.

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