Research with his own approach on norovirus as well as various other pathogens causing food poisoning
 
 
Dr. Shimamoto specializes in food hygienics, a discipline that deals with food safety. His main research interest focuses on microorganisms that cause food poisoning, such as E. coli O157, Salmonella, Vibrio parahaemolyticus, Campylobacter and norovirus. In Japan, norovirus is responsible for more than half of the total number of food poisoning patients.

“In terms of preventing food poisoning, how to disinfect norovirus is an important issue. Our laboratory conducts research related to norovirus as one of a number of pathogens and has achieved some results,” says Dr. Shimamoto.

Norovirus is a virus that is particularly difficult to study. “Norovirus only infects humans and can proliferate only in human intestines. Unlike other viruses, therefore, it is not possible to grow norovirus using cultured cells or to infect animals with it. The virus cannot be proliferated evien by human cultured cells. For these reasons, research has not been well advanced.”
In recent years, outbreaks of norovirus are often reported in winter. According to Dr. Shimamoto, the reasons are as follows: “One reason is that norovirus is ‘highly infectious.’ There are about 10 billion noroviruses in one gram of feces from a norovirus infected patient. The oral ingestion of 10 to dozens of noroviruses will cause infection. Infection is generally contracted orally but there are cases of air-borne infection caused by particles of dried vomit floating in the air.

Another reason is that norovirus is ‘highly resistant to various kinds of disinfectants.’ Viruses can usually be killed by alcohol but norovirus cannot. Special disinfection measures need to be used.”

  

 
Making efforts with the hope of developing a disinfectant that is safe and comfortable to use, what we finally came up with was “persimmon tannin.”
 
 
“Because of little progress in norovirus research, there is no treatment available even in the case of infection with norovirus. So, what is most important is to prevent food poisoning and prevent people from being infected,” says Dr. Shimamoto.

From a perspective of preventing food poisoning, his laboratory has long been engaged in developing a disinfectant that is effective against norovirus, through carrying out a joint research project with Altan Co. Ltd., which develops disinfectants.

“The Ministry of Health, Labor and Welfare recommends two methods for disinfecting norovirus: (1) application of chlorine bleach and (2) heating at 85°C or higher for one minute. In humans, (2) cannot be applied and (1) may cause rough skin and, if mixed with acid, may generate chlorine gas and, due to its toxicity, it cannot be used in cooking settings.
Our concept therefore has been ‘to develop a human-friendly disinfectant that is safe and comfortable to use’ from the very beginning.”
What he discovered in the process of his research was “persimmon tannin,” an extract from astringent persimmons. Persimmon tannin, a plant-derived ingredient with high protein aggregation ability, is safe when taken by mouth or applied to hands.

After successfully identifying the strong anti-noroviral effects of persimmon tannin, his laboratory acquired a patent for a new method of disinfection using persimmon tannin, which has already been commercialized. “There are no other disinfectants in the world that use persimmon tannin. In the five years after filing the patent application, we obtained patents in Japan, China and the United States.

In April 2013, Hiroshima University and Altan Co. Ltd. jointly received the Industry-Academia-Government Collaboration Award for small and medium-sized enterprises in the field of excellent new technology and products. The product we developed has been proven to be effective not only against norovirus but also against about 20 different kinds of viruses, including influenza virus and viral pathogens causing measles and polio. This is a truly a very widely effective and powerful disinfectant,” says Dr. Shimamoto.

  
 
Contribution to society by supplying disinfectants against norovirus and developing its detection methods. Continuing efforts into the future to produce more results.
 

  Dr. Shimamoto was initially interested in human health. After graduating from the School of Pharmacy, he engaged in research on the transport of nutrients into bacterial cells. In the research process, he became involved in research on pathogens, when he started realizing the importance of research on microorganisms causing diseases in humans. “I thought research on how to control such microorganisms would be directly useful to people, and interesting, so I switched my research interest.”

“And now I enjoy the challenge of launching out products useful to people and feel satisfaction of contributing to society,” says Dr. Shimamoto. Despite the fact that it is still difficult to conduct research related to norovirus, he has also developed a new detection method for norovirus using human intestinal cells, which is one of the reasons why his research is regarded as advanced. “In Japan we cannot perform experiments in humans by oral ingestion. So, we use a method for detecting genes in a virus to prove the efficacy of disinfectants. The method itself is popular but I think our team is the only one that uses this method to evaluate disinfectants,” says Dr. Shimamoto.
He has received many offers to conduct various kinds of research projects jointly with his laboratory based on his cutting-edge research. “I hope to continue doing more influential research. At the same time, I also hope to develop outstanding researchers who will play a useful role for society.”
 
Tadashi Shimamoto
Professor
Laboratory of Food Microbiology and Hygiene

April 1, 1986 to December 31, 1997: Research Associate, Okayama University
June 15, 1991 to June 30, 1994: Postdoctoral Fellow, the University of Medicine and Dentistry of New Jersey (UMDNJ)
January 1, 1998 to March 31, 2007: Associate Professor, Hiroshima University
April 1, 2004 to September 30, 2004: Part-Time Lecturer, Suzugamine Women’s College
April 1, 2007 to February 28, 2009: Associate Professor, Hiroshima University
March 1, 2009 to present: Professor, Hiroshima University

Posted on Jan 28, 2014