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Plasmid profiles of drug resistant Shigella boydii types 1-5, 8, 10, 12-14 from Ethiopia (1974-85)
1Department of Microbiology, National Research Institute of Health, Addis Ababa, Ethiopia.
Abstract:
Plasmid profile analysis by agarose gel electrophoresis was performed on 42 drug resistant strains of Shigella boydii serotypes 1-5, 8, 10, 12-14, collected between 1974 and 1985 from endemic cases of shigellosis in Ethiopia, and their Escherichia coli K12 transconjugants. Resistance factors (R factors) were further characterized by incompatibility testing. Patterns of small plasmids, less than 15 kb, were similar within each of the individual S. boydii serotypes. Plasmids of about 3.3-3.7 kb were found in all strains of serotypes 2 and 4. Plasmids of about 4.3-4.6 kb were found in about 86% of strains. Serotypes 1, 2 and 3 were characterized by plasmids of about 5.6-5.7 kb. The 6.4-6.7 kb plasmid was found consistently in serotypes 1, 2, 3, 5, 8, 12 and 13 which were resistant to SSu or had an SSu resistance component in their phenotypes. Large plasmids (155-186 kb) were found in most S. boydii strains. Conjugative drug resistance plasmids, most often coding for three or less drugs, were found in about 26% of drug resistant strains. R-factors, coding for AT resistance (in types 2 and 8), and ASSuT resistance (in type 4), were compatible with all reference plasmids tested. Plasmids belonging to incompatibility groups X and N were found in serotypes 5 and 10, respectively.
Insights
Plasmid analysis of Shigella boydii revealed serotype-specific small plasmids and large plasmids in most strains. Conjugative resistance plasmids were identified in a quarter of drug-resistant isolates.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Shigella boydii is a significant cause of shigellosis.
- Drug resistance in bacterial pathogens is a growing public health concern.
- Understanding plasmid-mediated resistance is crucial for combating infectious diseases.
Purpose of the Study:
- To characterize plasmid profiles of drug-resistant Shigella boydii strains.
- To investigate the association between specific plasmids and serotypes.
- To analyze the characteristics of resistance factors (R factors) in these strains.
Main Methods:
- Agarose gel electrophoresis was used for plasmid profile analysis.
- Escherichia coli K12 was used for conjugation experiments.
- Incompatibility testing was performed to characterize R factors.
Main Results:
- Serotype-specific patterns of small plasmids (<15 kb) were observed.
- Plasmids of specific sizes (3.3-3.7 kb, 4.3-4.6 kb, 5.6-5.7 kb, 6.4-6.7 kb) were associated with particular S. boydii serotypes.
- Large plasmids (155-186 kb) were prevalent in most strains.
- Conjugative drug resistance plasmids were found in 26% of resistant strains.
- R-factors conferring resistance to AT and ASSuT were compatible with reference plasmids.
- Plasmids from incompatibility groups X and N were identified in serotypes 5 and 10, respectively.
Conclusions:
- Plasmid profiles exhibit diversity and serotype specificity in Shigella boydii.
- Specific plasmids may play a role in the resistance patterns observed in different serotypes.
- The characterization of R factors provides insights into the genetic basis of drug resistance in Shigella.
- Further research is needed to understand the functional role of these plasmids in virulence and resistance.