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Modified peptidoglycan transpeptidase activity in a carbenicillin-resistant mutant of Pseudomonas aeruginosa 18s
Abstract:
A carbenicillin-resistant mutant of Pseudomonas aeruginosa 18s was found to possess peptidoglycan transpeptidase activity significantly more resistant to inhibition by benzyl penicillin, ampicillin, carbenicillin, and cephaloridine than that of the parent strain. The mutant was more resistant than the parent strain to all of the beta-lactam antibiotics tested, and 50% inhibition values for these compounds against membrane-bound model transpeptidase activity paralleled this increase. The resistance of the mutant to kanamycin, streptomycin, and chloramphenicol was unchanged.
Insights
A carbenicillin-resistant Pseudomonas aeruginosa mutant showed increased resistance to beta-lactam antibiotics, including penicillin and ampicillin. This enhanced resistance in peptidoglycan transpeptidase activity did not affect other antibiotic classes.
Area of Science:
- Microbiology
- Biochemistry
- Pharmacology
Background:
- Pseudomonas aeruginosa is an opportunistic pathogen known for its intrinsic and acquired resistance to antibiotics.
- Beta-lactam antibiotics, including penicillin and ampicillin, are crucial for treating bacterial infections.
- Understanding the mechanisms of antibiotic resistance is vital for developing effective therapeutic strategies.
Purpose of the Study:
- To investigate the characteristics of a carbenicillin-resistant mutant of Pseudomonas aeruginosa.
- To determine the effect of carbenicillin resistance on peptidoglycan transpeptidase activity.
- To assess the cross-resistance profile of the mutant to various classes of antibiotics.
Main Methods:
- Isolation and characterization of a carbenicillin-resistant Pseudomonas aeruginosa mutant (strain 18s).
- Assay of peptidoglycan transpeptidase activity in both the parent and mutant strains.
- Determination of 50% inhibition (IC50) values for various beta-lactam antibiotics against the transpeptidase activity.
- Testing the susceptibility of the mutant to other antibiotic classes, including aminoglycosides and chloramphenicol.
Main Results:
- The carbenicillin-resistant mutant exhibited significantly higher resistance to inhibition of peptidoglycan transpeptidase activity by benzyl penicillin, ampicillin, carbenicillin, and cephaloridine compared to the parent strain.
- The mutant displayed increased resistance to all tested beta-lactam antibiotics, with IC50 values for membrane-bound transpeptidase activity correlating with this resistance.
- No change in resistance was observed for kanamycin, streptomycin, or chloramphenicol, indicating specific resistance mechanisms.
Conclusions:
- Carbenicillin resistance in Pseudomonas aeruginosa is associated with altered peptidoglycan transpeptidase activity.
- The observed resistance is specific to beta-lactam antibiotics and does not confer broad-spectrum cross-resistance.
- These findings contribute to understanding beta-lactam resistance mechanisms in Pseudomonas aeruginosa.