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[Shigella dysenteriae strains possessing a new serovar isolated from imported diarrheal cases in Japan]
S Matsushita1, Y Noguchi, Y Yanagawa
1Department of Microbiology, Tokyo Metropolitan Research Laboratory of Public Health.
Abstract:
Two Shigella strains (93-119 and 95-619) isolated from stool cultures of imported diarrheal cases in Japan, did not react to any antisera of the established SHigella serovars. These strains had the typical biochemical characteristics of Shigella dysenteriae, and were biochemically identical to each other. Both strains were positive in the Serény test and other tests for invasiveness; these indicate that they can cause shigellosis in humans. The results of antigenic analysis showed that they did not belong to any of the recognized or provisional serovars, and were serologically indistinguishable. Strain 93-119 is designated as the test strain for this new serovar.
Insights
Two novel Shigella dysenteriae strains were identified in Japan. These invasive strains represent a new serovar, indicating potential challenges in diagnosing shigellosis.
Area of Science:
- Microbiology
- Infectious Diseases
- Bacteriology
Background:
- Shigella species are a leading cause of bacterial dysentery worldwide.
- Accurate serological classification is crucial for epidemiological surveillance and outbreak investigation.
- Undetermined Shigella serovars can complicate diagnosis and control efforts.
Purpose of the Study:
- To characterize two previously unidentified Shigella strains isolated from imported diarrheal cases in Japan.
- To determine the biochemical and antigenic properties of these novel strains.
- To establish a new serovar for these distinct Shigella isolates.
Main Methods:
- Isolation and culturing of Shigella strains from stool samples.
- Biochemical testing to confirm Shigella dysenteriae characteristics.
- Serological analysis using established antisera.
- Invasiveness testing, including the Serény test.
Main Results:
- Two strains, 93-119 and 95-619, exhibited typical Shigella dysenteriae biochemical profiles.
- Both strains were biochemically identical and invasive, confirmed by the Serény test.
- Antigenic analysis revealed no reactivity with existing Shigella antisera, indicating a new serovar.
- Strain 93-119 was designated as the reference strain for this novel serovar.
Conclusions:
- The identified strains represent a new, previously unrecognized Shigella serovar.
- These findings highlight the ongoing evolution of Shigella and the need for continuous surveillance.
- The discovery of new serovars underscores the importance of comprehensive diagnostic methods for infectious diarrhea.