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Published on: November 7, 2018
Molecular epidemiology of Shigella sonnei in Pima County, Arizona: evidence for a Mexico-related plasmid
C M Litwin1, K J Ryan, S Chipowsky
1Department of Pathology, University of Arizona College of Medicine, Tucson 85724.
Abstract:
In 1984, the incidence of shigellosis was 32.4 per 100,000 population in Pima County, Arizona. To investigate sources, Shigella isolates and epidemiologic data were collected for 79 cases of infection with Shigella sonnei, the most common species. Since S. sonnei has a single serotype, plasmid isolation was attempted to refine the epidemiologic analysis. There were seven plasmid patterns containing 17, 13, 4, 22, 9, 2, and 3 isolates. Twelve of 17 isolates associated with recent travel to Mexico were in a group distinguished by a 5.1-kilobase (kb) plasmid. This plasmid was used to probe Southern blots of plasmids from strains of all groups. The Mexico-related plasmid probe hybridized to all the 5.1-kb plasmids and to 5.5- and 7.4-kb plasmids from three other groups. Of the 79 isolates, 50 contained plasmids homologous to the Mexico-related plasmid probe, suggesting association with travel to Mexico.
Insights
Travel to Mexico was linked to Shigella sonnei infections in Pima County, Arizona. A specific 5.1-kilobase plasmid found in isolates from travelers suggests a common source for these Shigella sonnei infections.
Area of Science:
- Microbiology
- Epidemiology
- Infectious Diseases
Background:
- Shigellosis incidence in Pima County, Arizona was 32.4 per 100,000 population in 1984.
- Shigella sonnei was the most common species identified.
- Traditional serotyping is limited for S. sonnei due to its single serotype.
Purpose of the Study:
- To investigate the sources of Shigella sonnei infections.
- To refine epidemiologic analysis using plasmid profiles.
- To identify potential links between travel and infection.
Main Methods:
- Collected Shigella isolates and epidemiologic data from 79 cases.
- Performed plasmid isolation to differentiate strains.
- Utilized Southern blot hybridization with a 5.1-kb plasmid probe.
Main Results:
- Seven distinct plasmid patterns were identified among the isolates.
- A 5.1-kilobase (kb) plasmid distinguished isolates associated with travel to Mexico.
- The Mexico-related plasmid probe hybridized to 50 of 79 isolates, including those with 5.1-kb, 5.5-kb, and 7.4-kb plasmids.
Conclusions:
- Plasmid analysis revealed potential common sources for Shigella sonnei infections.
- A significant association was found between travel to Mexico and specific plasmid types.
- This suggests travel as a contributing factor to shigellosis outbreaks.
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