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Plasmid-coded ampicillin resistance in Haemophilus ducreyi
Abstract:
Seven of the 96 ampicillin-resistant isolates of Haemophilus ducreyi reported in the preceding article (Bilgeri et al., Antimicrob. Agents Chemother. 22:686-688, 1982) were investigated and found to harbor plasmids of 3.95, 5.2, 5.8, and 6.4 megadaltons. All except the 5.8-megadalton plasmid have been shown to code for beta-lactamase. The 6.4- and 5.2-megadalton plasmids of three isolates were conjugally transferable to a streptomycin-resistant mutant of H. ducreyi at high frequencies, perhaps due to the presence in these strains of a high-molecular-weight plasmid.
Insights
Seven ampicillin-resistant Haemophilus ducreyi isolates harbor plasmids, with most coding for beta-lactamase. Some plasmids were transferable, indicating potential for antibiotic resistance spread in this bacterium.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Ampicillin resistance is a growing concern in Haemophilus ducreyi infections.
- Previous studies identified ampicillin-resistant isolates of H. ducreyi.
Purpose of the Study:
- To investigate the genetic basis of ampicillin resistance in H. ducreyi.
- To characterize the plasmids harbored by ampicillin-resistant H. ducreyi isolates.
- To determine the transferability of these plasmids.
Main Methods:
- Plasmid DNA isolation and characterization from H. ducreyi isolates.
- Conjugation experiments to assess plasmid transferability.
- Detection of beta-lactamase activity associated with plasmids.
Main Results:
- Seven ampicillin-resistant H. ducreyi isolates harbored plasmids of varying sizes (3.95, 5.2, 5.8, and 6.4 megadaltons).
- All plasmids, except the 5.8-megadalton one, were associated with beta-lactamase production.
- The 6.4- and 5.2-megadalton plasmids were efficiently transferred to a streptomycin-resistant H. ducreyi mutant via conjugation.
Conclusions:
- Plasmids play a significant role in ampicillin resistance in H. ducreyi.
- Beta-lactamase production is a key mechanism of resistance mediated by these plasmids.
- The conjugal transferability of certain plasmids suggests a mechanism for the dissemination of antibiotic resistance within H. ducreyi populations.