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Imipenem and meropenem induced resistance to beta-lactam antibiotics in Pseudomonas aeruginosa
A Giacometti1, F M Siquini, O Cirioni
1Clinica delle Malattie Infettive, Ospedale Umberto I, Ancona, Italy.
Abstract:
The ability of imipenem and meropenem in subinhibitory concentrations to influence the results of disk diffusion susceptibility tests was assessed. Selection of stably derepressed mutants resistant to beta-lactam antibiotics other than carbapenems was also investigated. Beta-lactams were shown to be subject to carbapenem-mediated antagonism in the disk diffusion test. On the other hand in vitro selection of stably derepressed mutants resistant to other beta-lactams could not be demonstrated.
Insights
Subinhibitory concentrations of imipenem and meropenem can interfere with disk diffusion tests for beta-lactam antibiotics. However, these carbapenems did not promote the in vitro selection of resistant mutants to other beta-lactams.
Area of Science:
- Microbiology
- Antimicrobial Resistance
- Clinical Diagnostics
Background:
- Disk diffusion susceptibility testing is a common method for determining bacterial susceptibility to antibiotics.
- Carbapenems like imipenem and meropenem are broad-spectrum beta-lactam antibiotics.
- Subinhibitory antibiotic concentrations can sometimes influence test results or promote resistance development.
Purpose of the Study:
- To investigate the effect of subinhibitory concentrations of imipenem and meropenem on disk diffusion susceptibility tests.
- To determine if these carbapenems could select for stably derepressed mutants resistant to other beta-lactam antibiotics.
Main Methods:
- Disk diffusion susceptibility tests were performed using imipenem and meropenem at subinhibitory concentrations.
- Bacterial cultures were challenged to assess the in vitro selection of stably derepressed mutants resistant to other beta-lactams.
Main Results:
- Carbapenem-mediated antagonism was observed in disk diffusion tests, indicating interference with the susceptibility results for other beta-lactams.
- In vitro selection of stably derepressed mutants resistant to beta-lactams other than carbapenems was not demonstrated.
Conclusions:
- Subinhibitory carbapenem concentrations can negatively impact the accuracy of disk diffusion susceptibility testing for other beta-lactams.
- The study did not find evidence that imipenem or meropenem promote the emergence of resistance to other beta-lactams through stable mutant selection.