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Chromosomally integrated conjugative plasmids are common in antibiotic-resistant Haemophilus influenzae
Abstract:
Twenty-three highly antibiotic-resistant strains of Haemophilus influenzae and two of Haemophilus parainfluenzae without detectable large plasmids were examined for conjugative transfer of their resistance to H. influenzae strain Rd or to other strains. Very inefficient transfer was observed for 18 H. influenzae strains and 1 H. parainfluenzae strain. All H. influenzae transcipients carried a large plasmid, and they were in turn efficient donors of their resistances in standard conjugation crosses with isogenic recipients. This was not seen for the H. parainfluenzae transcipients. It is concluded that most of the original antibiotic-resistant cultures carried an integrated conjugative R plasmid which had been excised in a few cells in each population. It was these cells which transferred resistance in the primary crosses.
Insights
Antibiotic resistance transfer in Haemophilus bacteria was inefficient, suggesting integrated R plasmids were responsible. Excised plasmids in a few cells facilitated resistance transfer in these strains.
Area of Science:
- Microbiology
- Genetics
- Molecular Biology
Background:
- Antibiotic resistance in Haemophilus species poses a significant public health threat.
- Understanding the mechanisms of resistance transfer is crucial for developing effective treatment strategies.
Purpose of the Study:
- To investigate the conjugative transfer of antibiotic resistance in Haemophilus influenzae and Haemophilus parainfluenzae strains.
- To identify the role of plasmids in the dissemination of antibiotic resistance.
Main Methods:
- Conjugation experiments were performed using antibiotic-resistant Haemophilus strains and susceptible recipient strains (H. influenzae strain Rd).
- Transconjugants were analyzed for the presence of plasmids and their ability to donate resistance.
Main Results:
- Inefficient transfer of antibiotic resistance was observed in most tested strains.
- H. influenzae transconjugants acquired large plasmids and became efficient donors of resistance.
- H. parainfluenzae transconjugants did not exhibit similar plasmid acquisition or enhanced donation capabilities.
Conclusions:
- The findings suggest that antibiotic resistance in most of the studied H. influenzae strains is mediated by integrated conjugative R plasmids.
- Plasmid excision in a subset of cells appears to be the mechanism enabling primary resistance transfer.
- The distinct behavior of H. parainfluenzae suggests different resistance mechanisms or plasmid dynamics in this species.