Degree

Doctor of Philosophy (PhD)

Department

School of Nutrition and Food Sciences

Document Type

Dissertation

Abstract

Salmonella enterica and human norovirus (HuNoV) are the leading cause of bacterial and viral gastroenteritis worldwide, respectively. One of the most important transmission routes of these pathogens is contaminated surfaces. In this study, we investigated the survival and the disinfection of Salmonella enterica serovar Typhimurium (S. Typhimurium) and HuNoV on selected consumer contact surfaces.

In the case of S. Typhimurium, formica laminate, stainless steel, and plastic cutting board surfaces were inoculated with different microbial loads of cells collected at log (6 h), stationary (24 h), or LTS (14 days) phases. The disinfection efficacy of two disinfectants (sodium hypochlorite or hydrogen peroxide) against Salmonella at log, stationary, and LTS phases on those surfaces was also studied. Factors such as initial microbial load and time waited before disinfection were considered. Results showed that, LTS phase cells survived better than stationary and log phase cells with the greatest survivor population (5.8 log10 CFU/cm2) recorded on laminate surface at 2 h after inoculation. Also, hydrogen peroxide was totally successful at eliminating Salmonella from all surfaces regardless of all factors. At 24 h prior to disinfection, LTS cells were the most resilient ones to sodium hypochlorite where disinfection efficacy ranged from 26 to 35% at a microbial load of 6 log10 CFU/cm2.

In the case of HuNoV, the survival of strain GII.4 Sydney on three commonly touched airplane cabinet surfaces (seat leather, plastic tray table, and seatbelt) was investigated for 30 days, with and without additional organic load. Moreover, the anti-viral efficacy of three anti-norovirus EPA registered disinfectants was examined under the same conditions. Results showed that HuNoV was highly stable on all surfaces where it was detected at high titers (>4 log10 genomic copies) for up to 30 days on all three surfaces when additional organic load was present.

The EPA-registered disinfectants used at manufacturer’s recommended contact time failed to inactivate HuNoV beyond 4 log10, a reduction value required by the EPA for a product to claim antiviral activity on non-porous surfaces.

These finding emphasize the environmental stability of these pathogens, and that multiples factors must be considered in order to achieve adequate sanitation.

Date

6-2-2018

Committee Chair

Xu, Wenqing

Available for download on Wednesday, May 28, 2025

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