Laboratory of Veterinary Microbiology

run by Drs. Okamura and Aikawa

Section of Applied Veterinary Sciences, Division of Veterinary Sciences
Department of Veterinary Medicine
Obihiro University of Agriculture and Veterinary Medicine

Toward control of bacterial infections...

Our laboratory conducts research to elucidate the host-specific infection and pathogenesis mechanisms exhibited by pathogenic bacteria in order to control and eradicate bacterial infections in livestock and poultry. Through this research, we also aim to understand the history of co-evolution between pathogenic bacteria and host animals, and to contribute to "stable food supply," "food safety," and "control of zoonosis," which are issues to be solved in the 21st century, as well as to deliver results that will lead to control of related bacterial infections in humans.

What’s new

2024.03.19 An undergrad graduated. 
2024.02.02 Two JICA trainees joined from Nigeria and Palestin.
2023.09.01 Dr. Aikawa joined as an associate professor.
2023.08.26 Mr. Suzuki (6th-year undergrad) received the Branch Meeting Aword of Excellence at the 88th Annual Conference of the Japanese Society for Bacteriology Hokkaido Branch.
2023.03.17 Okamura gave a talk at Workshop #5 in the 96th Annual Meeting of Japanese Society for Bacteriology.
2023.02.10 A JICA trainee joined from Ethiopia.
2022.10.29 Okamura chaired the 2nd Seminar of the Japan Livestock Infection Control Network (JLIC).
2022.03.05 Okamura chaired the 1st Seminar of the Japan Livestock Infection Control Network (JLIC).
2021.12.01 A 4th year undergrad joined.
2021.10.11 The website launched.
2021.01.01 Okamura newly appointed.


Our research focuses primarily on salmonellosis in livestock and poultry.

Salmonella spp. are commonly known as the causative agents of food poisoning and have been classified into up to 2,700 serotypes (serovars) according to the combination of somatic and 2 flagellar antigens. Most serovars are so-called generalists and cause gastrointestinal symptoms in a variety of animals (food poisoning in humans and diarrhea in livestock, mainly in young animals), but rarely cause death. On the other hand, less than 10 serotypes are highly host-specific, infecting only certain animals and causing systemic infection and septicemia, resulting in death of infected animals in an acute phase. Pregnant animals infected with these serovars can also cause abortions, and offspring infected in utero or ova by vertical transmission can become carriers of the organism and cause further horizontal transmission. However, the mechanism that causes this strong host-specific pathogensis and tissue tropism to the reproductive organs has not yet been elucidated.
Using Salmonella as a model, we are conducting research to elucidate the mechanisms that cause host-specific pathogensis and tissue tropism. We believe that clarifying these mysteries will not only help us understand the history of co-evolution of pathogens with their host animals, but also provide insight into the transmission mechanisms of zoonotic diseases that affect a wide variety of animals.
Elucidation of the mechanisms of host specificity and tissue tropism in the infection and pathogenesis of pathogens

Fowl typhoid is an acute fatal septicemic disease of chickens caused by infection with serovar Gallinarum biovar Gallinarum. Because of the economic damage posed worldwide, it is included on the World Organisation for Animal Health (WOAH) list of diseases, and in Japan, it is designated as a legally contagious disease under the Livestock Infectious Disease Prevention Law. Currently, a live vaccine against fowl typhoid is used in endemic countries, but its efficacy is unstable, and the development of an effective new vaccine or alternative prophylactic method is desired. However, the virulence factors of the pathogen and the mechanism of fowl typhoid pathogenesis involving these factors are still poorly understood. We have identified 50 genes that are thought to be important in the pathogenesis of fowl typhoid and the virulence of the bacteria. Based on these results, we are trying to elucidate the whole picture of host-specific pathogenic mechanisms. We are also working to elucidate the mechanism of transovarian infection by analyzing the tissue tropism of biovar Pullorum to the ovary.

Establishment of monitoring and preventive measures for bovine salmonellosis

Bovine salmonellosis is known to occur frequently in Hokkaido. Those caused by serovars Typhimurium and Dublin are designated as notifiable infectious diseases, and have become a major problem because of the economic damage caused to affected farms. In particular, Dublin can cause abortions in pregnant cows and is often not excreted in the feces, making it difficult to detect infected cows by fecal examination. Therefore, we are conducting combined bacterial and serological monitoring on several farms to determine at what stage the herd becomes infected with Salmonella and to establish measures to prevent outbreaks of salmonellosis, including encouraging vaccination.

Elucidation of pathogenic mechanisms of equine paratyphoid

Equine paratyphoid caused by serovar Abortusequi has historically occurred sporadically in Hokkaido. This disease is characterized by contagious abortions and multifocal abscesses, and is designated as a notifiable infectious disease. Because of the sharp decline in outbreaks in developed countries and its exclusion from the WOAH list of diseases, the exact status of outbreaks worldwide is not known, but outbreaks are still occurring in South America, Europe, and Asia. Detailed research on this serotype and equine paratyphoid has made little progress worldwide. In response to the recent outbreaks of equine paratyphoid in the Tokachi region of Hokkaido, we are now analyzing the pathogenicity and pathogenesis of this organism.

Establishment of the countermeasures to reduce contamination of chicken flocks and poultry meat by food-borne pathogens

Foodborne diseases caused by contaminated poultry are increasing constantly. The main causative agents are Salmonella and Campylobacter. The risk of foodborne diseases cannot be reduced only by measures taken at the consumption stage, such as cooking the meat thoroughly before consumption. Therefore, we have been investigating the contamination status of poultry flocks and meat at farms and poultry slaughterhouses to establish measures to reduce foodborne bacterial contamination of poultry flocks, going back to the poultry slaughtering stage, which is upstream of the poultry food chain, and even to the production stage on farms. The future challenge is to elucidate the route of introduction of Salmonella and Campylobacter into the farm.


This laboratory has 2 faculty members, Okamura and Aikawa, and one supporting stuff, Dr. Nahid RAHMAN. We are now recruiting new 4th-year undergrads and graduate students. We hope to enjoy research with young people who have enthusiasm for both study and fun.

Masashi OKAMURA, D.V.M, Ph.D.



Chihiro AIKAWA,

Associate professor

Main classes

V2 Microbiology I
V3 Microbiology II
V3 Practical training in Microbiology
V3 Infectious Disease
V3 Practical training in Infectious diseases
V3 Practical training in Animal health 
V4 Practical training in Food hygiene 
M Veterinary Life Science
M Pathobiology, Etiology and Control of Animal Diseases I


Okamura’s office and lab: Rm# S2102, Research Bldg 1
Obihiro University of Agriculture and Veterinary Medicine
Obihiro, Hokkaido 080-8555, Japan
Okamura:+81-155-49-5389; okamuram[at]obihiro.ac.jp
Aikawa:+81-155-49-5515; caikawa[at]obihiro.ac.jp

Last updated April 01, 2024

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