Naturally Occurring Virucidal Agents

March 2015

Plant extracts and juices that have antimicrobial properties could be useful alternatives to harsh chemicals for disinfecting food-contact surfaces. Natural antimicrobials have been recently shown to have antiviral properties, including activity against hepatitis A virus and human norovirus surrogates.

The purpose of this study was to determine the efficacy of several natural antimicrobials, alone and in combination with surfactants, against hepatitis A virus (HAV) and murine norovirus (MNV-1), a surrogate for human norovirus.

Grape seed extract, white vinegar, pycogenol, pomegranate juice, cranberry juice, and sodium bicarbonate were evaluated for their efficacy in killing MNV-1 and HAV. A combination of sodium dodecyl sulfate (SDS) and potential antimicrobials with a pH below 4 was tested; basic compounds combined with benzalkonium chloride were tested. Following a 1-minute contact time at 23ºC±2ºC, antimicrobials were neutralized using 10% fetal bovine serum in phosphate buffered saline and an acid/base neutralizer. Virucidal activity was quantified using plaque assays (n=3).

MNV-1 (average inoculum titer was 6.17 log PFU/ml) was reduced by 2.33 and 2.65 log PFU/ml when treated with 0.01% or 0.1% grape seed extract, respectively, and by 1.59 log PFU/ml in 0.1% pycogenol. Undiluted cranberry juice, pomegranate juice, and white vinegar without SDS were ineffective (< 1 log PFU/ml reduction). Combined with 0.1% SDS, reductions of 1.48 and 1.38 log PFU/ml were observed for cranberry juice and white vinegar, respectively. Infectious MNV-1 was reduced by < 0.5 log PFU/ml by treatment with 0.1% SDS.

Reductions of HAV (average inoculum titer was 5.98 log PFU/ml) in 0.01% grape seed extract, 0.1% grape seed extract and 1% pycogenol were 0.75, 2.00 and 1.33 log PFU/ml, respectively. Sodium bicarbonate (5%) without benzalkonium chloride did not inactivate HAV; however, combined with benzalkonium chloride, a 1.22-log PFU/ml reduction was observed. Treatment in benzalkonium chloride treatment reduced infectious HAV by < 0.5 log PFU/ml.

Results suggest that lethal properties of some natural antimicrobials against foodborne MNV-1 and HAV can be enhanced by pairing with surfactants. Combinations of these antimicrobials and SDS show promise for use as food-contact surface disinfectants, thereby preventing transmission of foodborne viruses.