Date of Award

5-2014

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Microbiology

Advisor

Jiang, Xiuping

Committee Member

McNealy , Tamara

Committee Member

Pettigrew , Charles

Committee Member

Fraser , Angela

Abstract

Human Noroviruses (HuNoV) are the leading cause of acute gastroenteritis worldwide as well as the leading cause of foodborne disease in the U.S. HuNoV can persist in the environment even after proper disinfection, making preventing HuNoV infections and controlling subsequent outbreaks extremely challenging. Epidemiological evidence suggests that soft surfaces may be a relevant source of HuNoV due to the inability to effectively decontaminate. The objectives of this study were to: 1) review the current published literature on prevalence, transmission, and disinfection pertaining to HuNoV and surrogates with an emphasis on soft surfaces as fomites, 2) optimize a recovery method capable of efficiently recovering microorganisms from cotton fabric, and 3) develop a method for assessing the recovery and disinfection of viruses on soft surfaces using two HuNoV surrogates, Feline Calicivirus (FCV) and Murine Norovirus (MNV). In order to determine the most efficient method for recovery of microorganisms from soft surfaces we evaluated the recovery efficiency (RE) of Escherichia coli from cotton swatches using three elution-agitation methods. We found that RE using stomaching, sonication, and vortexing was not significantly different (p>0.05), resulting in approximately 21-30% RE. The most efficient method of recovery was achieved using a combination of sonication for 5 min at 40 kHz prior to stomaching for 5 min at 260 rpm. This resulted in a RE of 65% of E. coli dried on cotton swatches. To evaluate our proposed method for testing disinfectants against HuNoV on soft surfaces, we compared the recovery efficiency and disinfection efficacy of FCV and MNV bound to glass, polyester, and cotton. FCV and MNV were recovered from glass, cotton and polyester at 35.22, 5.59, 0.15% and 24.27, 14.69, and 0.85%, respectively. Two sanitizers, bleach (5,000 ppm NaOCl) and Oxivir (2,656 ppm H2O2) were able to inactivate FCV (2.5-4.7 reduction) below the limit of detection on all 3 surface types. Only bleach was able to inactivate MNV (2.2-3.8 log reduction) below the limit of detection on all 3 surface types. Inactivation of MNV by Oxivir resulted in a reduction of 1.3, 0.57, and 0.17 log pfu/ml on glass, polyester, and cotton, respectively. Reduction of viral RNA measured by RT-qPCR using bleach resulted in 2.72-4.06 log reduction for FCV and 2.07-3.04 log reduction for MNV on all 3 surface types. Reduction of viral RNA by Oxivir resulted in 1.89-3.4 log reduction for FCV and 0.54-0.85 log reduction for MNV. We found that the virus type had a significant (p<0.001) influence on the recovery and disinfection of soft surfaces. In addition we found that recovery was also significantly different from non-porous, synthetic porous, and natural porous surfaces (P<0.05). The results of our study clearly indicate that both microorganism and surface type influence recovery efficiency and disinfection efficacy. Due to the low recovery observed on soft surfaces, further studies on recovery methods for soft surfaces are needed in order to document the 4 log reduction needed to establish virucidal efficacy. In addition we recommend that the use of FCV as a surrogate be carefully considered, as it may not be the most suitable surrogate for evaluating the efficacy of disinfectants against HuNoV.

Included in

Microbiology Commons

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