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Mutant prevention concentrations of imipenem and meropenem against Pseudomonas aeruginosa and Acinetobacter baumannii

E Dahdouh1, S H Shoucair1, S E Salem1

  • 1Clinical Microbiology Laboratory, Faculty of Medicine & Medical Science, University of Balamand, P.O. Box 100, Tripoli, Lebanon.

Thescientificworldjournal
|January 23, 2015
PubMed

Insights

The mutant prevention concentration (MPC) of carbapenems is useful against resistant Pseudomonas and Acinetobacter. MPC values correlate with resistance levels, not specific resistance mechanisms, guiding optimal antibiotic therapy.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Pharmacology

Background:

  • Carbapenem resistance in Pseudomonas spp. and Acinetobacter spp. poses a significant clinical challenge.
  • Understanding resistance mechanisms is crucial for effective antimicrobial stewardship.

Purpose of the Study:

  • To evaluate the utility of the mutant prevention concentration (MPC) of carbapenems against clinical isolates of Pseudomonas and Acinetobacter.
  • To investigate the relationship between MPC and carbapenem resistance mechanisms.

Main Methods:

  • Antibiotic Susceptibility Testing, Double Disk Synergy, and various phenotypic tests were used to detect resistance mechanisms.
  • Minimum Inhibitory Concentration (MIC) and MPC were determined via broth macrodilution and plate dilution.
  • Tested 10 clinical isolates of Pseudomonas spp. and Acinetobacter baumannii.

Main Results:

  • Four Acinetobacter baumannii strains produced MBL, two Oxacillinase, and one ESBL. Two Pseudomonas spp. isolates produced both KPC and MBL.
  • Resistant strains exhibited higher MPC values compared to susceptible strains.
  • Mutant Selection Window (MSW) depended on the degree of resistance, not specific mechanisms.

Conclusions:

  • The usefulness of MPC is value-dependent and recommended for individual isolate assessment before treatment.
  • Therapeutic strategies should consider T>MSW (time above mutant selection window) over T>MIC (time above minimum inhibitory concentration).

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