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Characterization and mobilization of nonconjugative plasmids encoding resistance to streptomycin and sulfanilamide
Y Araki1, M Inoue, H Hashimoto
1Laboratory of Drug Resistance in Bacteria, Gunma University School of Medicine.
Abstract:
Most of nonconjugative streptomycin (Sm)- and sulfanilamide (Su)- resistance of clinical isolates belonging to various species of Enterobacteriaceae and Pseudomonas were encoded by an Inc Q plasmid, molecular size of which was 5.5 Md. The SmSu plasmids were efficiently mobilized by Inc P plasmids between E. coli strains. Inc I group and Inc F group plasmids could mobilize the Inc Q plasmids at lower efficiencies. The Inc Q plasmid was also mobilized to various species of Enterobacteriaceae at high frequencies without accompanying the conjugative Inc P plasmid; as a result, most of the SmSu-resistant transconjugants were nontransferable. The above results may explain the wide distribution of nonconjugative SmSu strains among clinical isolates.
Insights
Most clinical streptomycin (Sm) and sulfanilamide (Su) resistance in Enterobacteriaceae and Pseudomonas is linked to nonconjugative Inc Q plasmids. These plasmids are mobilized by other plasmids, explaining the widespread occurrence of resistant strains.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Antibiotic resistance is a growing global health concern.
- Nonconjugative plasmids play a significant role in the dissemination of antibiotic resistance genes.
- Understanding plasmid mobility is crucial for controlling the spread of resistance.
Purpose of the Study:
- To investigate the genetic basis of streptomycin (Sm) and sulfanilamide (Su) resistance in clinical isolates.
- To determine the role of Inc Q plasmids in encoding SmSu resistance.
- To analyze the mobilization and transferability of Inc Q plasmids within Enterobacteriaceae and Pseudomonas.
Main Methods:
- Plasmid analysis of clinical isolates.
- Conjugation experiments using various Inc P, Inc I, and Inc F group plasmids.
- Mobilization assays to assess Inc Q plasmid transfer frequencies.
- Characterization of transconjugant resistance and transferability.
Main Results:
- Most nonconjugative Sm and Su resistance in clinical Enterobacteriaceae and Pseudomonas isolates was encoded by a 5.5 Md Inc Q plasmid.
- Inc P plasmids efficiently mobilized the Inc Q plasmids between E. coli strains.
- Inc I and Inc F plasmids showed lower efficiencies in mobilizing Inc Q plasmids.
- High-frequency mobilization of Inc Q plasmids to Enterobacteriaceae occurred without the conjugative Inc P plasmid, resulting in nontransferable SmSu-resistant transconjugants.
Conclusions:
- Inc Q plasmids are a major vehicle for nonconjugative SmSu resistance in clinical settings.
- The efficient mobilization of Inc Q plasmids by other plasmid groups facilitates their spread.
- The generation of nontransferable resistant strains through mobilization can explain their wide distribution among clinical isolates.