Determination of Carbapenem Resistance and Mutant Prevention Concentration Escherichia Coli and Klebsiella Pneumoniae Strains Producing Extended Spectrum Beta Lactamases and Plasmid Mediated Ampc Beta Lactamases

Objective: To determine mutant prevention concentrations of carbapenems and resistance development during carbapenem treatment of infections due to extended spectrum beta lactamase (ESBL) and/or pAmpC beta-lactamase producing bacteria. Method: Escherichia coli and Klebsiella pneumoniae isolates having imipenem and meropenem MIC= 256 µg/ml). In ESBL(+) strains, imipenem and meropenem even in very low MICs (0,015-0,06 µg/ml) have selected carbapenem resistant mutants in a rate of 50%. Conclusion: According to the results, i) ESBL and pAmpC production bring about selection of carbapenem resistant mutants even though strains are carbapenem susceptible in routine tests, ii) Infections caused by strains with carbapenem MICs in susceptible range but producing carbapenemase may have high probability of treatment failure, iii) Among carbapenems, doripenem and ertapenem have the lowest imipenem and meropenem have the highest potential for mutant selection