Related Experiment Videos
Penicillin-binding proteins and ampicillin resistance in Haemophilus influenzae
P M Mendelman1, D O Chaffin, G Kalaitzoglou
1Division of Infectious Diseases, Children's Hospital and Medical Center, Seattle, WA.
Abstract:
Ampicillin-resistant, non-beta-lactamase-producing isolates of Haemophilus influenzae contain a variety of penicillin-binding protein (PBP) patterns that differ from the single pattern of eight PBPs characteristic of susceptible strains. During genetic transformation of resistance, only some of the anomalies in PBP pattern were transformed, specifically those relating to the penicillin-binding capacities of PBPs 4 (Mr of 62,000) and 5 (Mr of 59,000) and, in some transformations, PBP 3 (Mr of 71,000). Comparison of the binding of penicillin by PBPs 4 and 5 of three resistant transformants (derived with DNA from different donors) revealed a decrease in the rate of PBP acylation and no appreciable change in the rate of deacylation as compared to the susceptible recipient. Thus, rapid turnover of these PBPs does not play a role. Retransformation studies confirm that altered PBPs 3, 4, and 5 are associated with resistance and suggest that these PBPs are major targets for the beta-lactam antibiotics in H. influenzae.
Insights
Ampicillin resistance in Haemophilus influenzae involves altered penicillin-binding proteins (PBPs). Genetic transformation studies reveal specific PBP changes linked to resistance, identifying PBPs 3, 4, and 5 as key targets for beta-lactam antibiotics.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Ampicillin-resistant Haemophilus influenzae strains exhibit diverse penicillin-binding protein (PBP) patterns compared to susceptible strains.
- Non-beta-lactamase-producing resistant isolates show unique PBP profiles.
Purpose of the Study:
- To investigate the specific penicillin-binding protein (PBP) alterations associated with ampicillin resistance in Haemophilus influenzae.
- To determine which PBP anomalies are transferable during genetic transformation and linked to resistance.
Main Methods:
- Genetic transformation experiments using DNA from resistant H. influenzae strains.
- Analysis of penicillin-binding capacities of PBPs in resistant transformants and susceptible recipients.
- Comparison of PBP acylation and deacylation rates.
Main Results:
- Specific PBP pattern anomalies, particularly in PBPs 4 and 5, were transformed during genetic transfer.
- Altered PBPs 3, 4, and 5 were confirmed to be associated with ampicillin resistance.
- A decreased rate of PBP acylation, not deacylation, was observed in resistant transformants.
Conclusions:
- Altered penicillin-binding proteins (PBPs) 3, 4, and 5 are crucial for ampicillin resistance in Haemophilus influenzae.
- These specific PBPs are identified as major targets for beta-lactam antibiotics in this bacterium.
- Rapid PBP turnover is not a mechanism contributing to ampicillin resistance.