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Plasmid-mediated beta-lactamase production in Neisseria gonorrhoeae
Abstract:
Several beta-lactamase-producing, penicillin-resistant strains of Neisseria gonorrhoeae were examined for R plasmids. Penicillin-resistant strains isolated from men returning from the Far East and their contacts contained a 4.4 x 10(6)-dalton plasmid in common. Transformation studies and the isolation of a spontaneous penicillin-susceptible segregant showed that the structural gene for beta-lactamase was part of the 4.4 x 10(6)-dalton plasmid. An additional penicillin-resistant gonococcal strain isolated in London was found to harbor a 3.2 x 10(6)-dalton R plasmid. Deoxyribonucleic acid (DNA)-DNA duplex studies revealed that the penicillin-resistant gonococcal isolates contained a significant portion (about 40%) of the transposable DNA sequence, TnA, which includes the beta-lactamase gene commonly found on R plasmids of the Enterobacteriaceae and Haemophilus influenzae.
Insights
Penicillin-resistant Neisseria gonorrhoeae strains carry R plasmids encoding beta-lactamase. These plasmids, particularly a 4.4 x 10(6)-dalton one, are linked to beta-lactamase production and contain the transposable DNA sequence TnA.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Neisseria gonorrhoeae is a significant cause of sexually transmitted infections.
- Emergence of antibiotic resistance, particularly penicillin resistance, poses a major public health threat.
- Beta-lactamase production is a key mechanism of penicillin resistance in Neisseria gonorrhoeae.
Purpose of the Study:
- To investigate the role of R plasmids in beta-lactamase-producing, penicillin-resistant Neisseria gonorrhoeae strains.
- To characterize the plasmids found in resistant gonococcal isolates.
- To determine the genetic basis of beta-lactamase production in these strains.
Main Methods:
- Isolation and characterization of R plasmids from Neisseria gonorrhoeae strains.
- Plasmid transformation studies.
- Isolation of penicillin-susceptible segregants.
- DNA-DNA hybridization (duplex studies) to analyze DNA sequences.
- Identification of the transposable DNA sequence TnA.
Main Results:
- Penicillin-resistant strains from the Far East and contacts shared a common 4.4 x 10(6)-dalton plasmid.
- Transformation studies confirmed the 4.4 x 10(6)-dalton plasmid carries the beta-lactamase structural gene.
- A distinct penicillin-resistant strain from London harbored a 3.2 x 10(6)-dalton R plasmid.
- Resistant isolates contained approximately 40% of the TnA transposable DNA sequence, including the beta-lactamase gene.
Conclusions:
- R plasmids play a crucial role in the penicillin resistance of Neisseria gonorrhoeae.
- The 4.4 x 10(6)-dalton plasmid is a common vehicle for the beta-lactamase gene in certain resistant strains.
- The presence of the TnA sequence highlights the genetic mobility of the beta-lactamase gene within Neisseria gonorrhoeae and its similarity to resistance mechanisms in other bacteria.