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R plasmids conferring multiple drug resistance from shigella isolated in Korea
Abstract:
The majority (85%) of shigella isolated in 1980 and 1981 in Korea were Shigella flexneri, the others were Sh. sonnei (14%) with only a small number of Sh. dysenteriae. Only 14 of the 459 strains of shigella isolated were susceptible to all 12 drugs tested, and 445 were resistant to three or more drugs. Strains multiply resistant to the six drugs, chloramphenicol (Cm), tetracycline (Tc), streptomycin (Sm), sulfisomidine (Su), ampicillin (Ap) and trimethoprim (Tp) were most frequently encountered, followed by those resistant to Cm, Tc, Sm, Su and Tp. The complete patterns of resistance to drugs except nalidixic acid and rifampin in approximately 73% of drug-resistant strains were co-transferred to Escherichia coli by conjugation, indicating that the resistance was R plasmid-mediated. Randomly selected R plasmids conferring various patterns of resistance markers were tested for the incompatibility groups, and almost all of them were classified into Inc FII. Two of three R plasmids conferring resistance to Cm, Tc, Sm and Su were classified into Inc B and one to Inc FII. Two R types with resistance markers of Cm, Tc, Sm and Ap were not classified with our standard plasmids used.
Insights
Most Shigella strains in Korea (1980-1981) were drug-resistant Shigella flexneri. Resistance patterns were often R plasmid-mediated, primarily belonging to Inc FII incompatibility groups.
Area of Science:
- Microbiology
- Infectious Diseases
- Genetics
Background:
- Shigella infections remain a significant public health concern globally.
- Understanding antimicrobial resistance patterns is crucial for effective treatment and control.
- Previous studies indicated emerging drug resistance in bacterial pathogens.
Purpose of the Study:
- To characterize the prevalence and antimicrobial resistance profiles of Shigella strains isolated in Korea.
- To investigate the genetic basis of drug resistance, specifically R plasmid mediation.
- To determine the incompatibility groups of the identified R plasmids.
Main Methods:
- Isolation and identification of Shigella strains from clinical samples.
- Antimicrobial susceptibility testing against 12 different drugs.
- Conjugation experiments to assess R plasmid-mediated resistance transfer to Escherichia coli.
- Incompatibility grouping of R plasmids using standard typing methods.
Main Results:
- Shigella flexneri constituted 85% of isolates, followed by Shigella sonnei (14%).
- A high prevalence of multidrug-resistant strains (445/459) was observed, resistant to three or more drugs.
- R plasmid-mediated resistance was confirmed in approximately 73% of drug-resistant strains, with most R plasmids belonging to Inc FII.
- Some R plasmids conferring resistance to chloramphenicol, tetracycline, streptomycin, and sulfisomidine were classified into Inc B or Inc FII.
Conclusions:
- Shigella flexneri is the predominant Shigella species in Korea, exhibiting extensive multidrug resistance.
- R plasmids play a significant role in the dissemination of antimicrobial resistance among Shigella strains.
- The prevalence of Inc FII and Inc B plasmids highlights their importance in mediating resistance in this pathogen.