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United States Department of Agriculture

Agricultural Research Service

Research Project: Molecular Biology of Human Pathogens Associated with Food

Location: Produce Safety and Microbiology Research

Title: Rice hull smoke extract inactivates Salmonella Typhimurium in laboratory media and protects infected mice against mortality

Authors
item Kim, Sung-Phil -
item Kang, Mi Young -
item Park, Jun Cheol -
item Nam, Seok Hyun -
item Friedman, Mendel

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 29, 2011
Publication Date: December 2, 2011
Citation: Kim, S., Kang, M., Park, J., Nam, S., Friedman, M. 2011. Rice hull smoke extract inactivates Salmonella Typhimurium in laboratory media and protects infected mice against mortality. Journal of Agricultural and Food Chemistry. 77:M80-M85. doi: 10.1111/j.750-3841.2011.02478.x.

Interpretive Summary: The inhibitory effect of a previously characterized rice hull smoke extract (Kim, S. P.; Yang, J. Y.; Kang, M. Y.; Park, J. C.; Nam, S. H.; Friedman M. Composition of liquid rice hull smoke and anti-inflammatory effects in mice. J. Agric. Food Chem. 2011, 59, 4570-4581) against Salmonella Typhimurium in laboratory media and in infected mice was determined with the aid of standard bacterial assay and an in vivo mouse model in which the extract was administered both intraperitoneally and orally as part of a standard diet. The results show that antimicrobial effectiveness of the extract approaches that of the widely used medicinal antibiotic vancomycin. The combination of the extract and vancomycin acted synergistically against the foodborne pathogens. Inclusion of rice hull liquid smoke extract as part of a standard mouse diet fed for two weeks decreased mortality of ten mice infected with lethal doses of the Salmonella. Photomicrographs of liver tissues indicate that the liquid smoke also protected the liver against Salmonella-induced pathological lesions. These results suggest that the rice hull derived liquid smoke has the potential to complement widely used wood-derived liquid smokes as antimicrobial flavor formulations for application to foods and feeds.

Technical Abstract: A recently discovered and characterized rice hull liquid smoke extract was tested for bactericidal activity against Salmonella Typhimurium using the disc-agar method. The Minimum Inhibitory Concentration (MIC) value of rice hull smoke extract was found to be 0.822% (v/v). The in vivo antibacterial activity of the smoke extract (1%, v/v) was also examined in an infected Balb/c mouse model. Mice infected with a sub-lethal dose of the pathogens were administered intraperitoneally a 1% solution of rice hull smoke liquid extract at four 12 h intervals during the 48 h experimental period. The results showed that the extract inhibited bacterial growth by 59.4, 51.4, 39.6 and 28.3% compared to 78.7, 64.6, 59.2 and 43.2% with the medicinal antibiotic vancomycin (20 mg/mL). Three consecutive administrations at 12 h intervals elicited the most effective bacterial effect of 75.0% and 85.5% growth reduction by rice hull smoke extract and vancomycin, respectively. The combination of the extract and vancomycin acted synergistically against the bacteria. Inclusion of the rice hull liquid smoke extract (1% v/w) into a standard mouse diet fed for two weeks decreased mortality of ten mice infected with lethal doses of the Salmonella. Photomicrographs of liver tissues indicate that the liquid smoke also protected the liver against Salmonella-induced pathological lesions. These results suggest that the rice hull derived liquid smoke has the potential to complement widely used wood-derived smokes as antimicrobial flavor formulations for application to foods and feeds.

Last Modified: 8/27/2014
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