Date of Graduation

5-2025

Document Type

Thesis

Degree Name

Master of Science in Food Science (MS)

Degree Level

Graduate

Department

Food Science

Advisor/Mentor

Gibson, Kristen E.

Committee Member

Acuff, Jennifer C.

Second Committee Member

Adams, Richard

Keywords

efficacy; hand hygiene; MS2; phi6; surrogate; Tulane virus

Abstract

Infectious disease transmission due to viruses such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), influenza virus, human noroviruses (HuNoV), and hepatitis A, can occur via person-to-person contact or contaminated surfaces. Effective hand hygiene, including hand washing and use of hand sanitizers, is considered a critical tool for the control of infectious disease transmission, as recommended by the United States Centers for Disease Control and Prevention and the World Health Organization. However, while research on hand washing efficacy is well-documented, research on hand sanitizer efficacy, particularly for foam-based products, remains limited. This research addressed critical gaps in the area of hand sanitizer efficacy, particularly with foam-based hand sanitizers which are widely used but generally underexplored. First, the recovery of bacteriophage phi6 (Φ6; a surrogate for enveloped viruses such as SARS-CoV-2) from the whole hands was optimized. Φ6 was applied on either the palmar surface or the whole hand, recovered based on wet or dry conditions using three eluents [lysogeny broth (LC), tryptic soy broth (TSB), and 1.5% beef extract (BE)] and three recovery methods [glove juice method (GJM), hand rinsing, and modified dish method]. Recovery methods, inoculum application type, and recovery basis significantly impacted Φ6 recovery. Study results revealed that GJM and dry basis recovery are not ideal for Φ6, however, to maximize Φ6f recovery from the hands, inoculum should be applied to the palmar surface and recovered using LC medium while the inoculum is still wet. The study also examined the in vitro efficacy of foam hand sanitizers against enveloped and non-enveloped viruses. The efficacy of one non-alcohol-based hand sanitizer (NABHS) and four alcohol-based hand sanitizers (ABHS) with benzalkonium chloride (BZK) and ethanol as active ingredients, respectively, were explored using Φ6 as a surrogate for enveloped viruses and bacteriophage MS2 (Emesvirus zinderi) and Tulane virus (TuV) as surrogates for non-enveloped viruses (e.g., HuNoV and hepatitis A) with an exposure time of 10 s. While Φ6 was completely inactivated (5.23 ± 1.64 log reduction), MS2 proved resistant to inactivation (0.04 ± 0.08 log reduction). Conversely, efficacy against TuV significantly varied across products, indicating that while 10 s may be sufficient to inactivate enveloped viruses, higher exposure time may be necessary to achieve similar log reductions against non-enveloped viruses such as human norovirus based on the tested surrogates. Finally, the in vivo efficacy of commercially available ABHS and NABHS against enveloped and non-enveloped viruses was evaluated, assessing varying dosing volumes and rubbing time. The findings revealed that the efficacy of the products is significantly affected by virus type, rubbing time, and overall formulation. Employing Φ6 as a surrogate for enveloped viruses yielded a significantly higher log reduction (2.83 ± 1.98) than MS2, the surrogate utilized for non-enveloped viruses (0.50 ± 0.53). Furthermore, when hands were rubbed until dry following hand sanitizer application, a significantly higher log reduction (2.69 ± 2.06) was observed compared to 10 s rubbing time (0.65 ± 0.75), which is typical among users.

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