Efeitos da 1,10-fenantrolina-5,6-diona e seus derivados metálicos sobre amostras clínicas de Klebsiella pneumoniae produtoras de carbapenemase KPC : potencial sinérgico com carbapenêmicos

Abstract

Infections caused by carbapenemase-producing Klebsiella pneumoniae KPC (KpKPC) pose a major threat to clinical practice as they are associated with high mortality rates and have scarce therapeutic options available. Currently, isolates resistant to all known antimicrobials have been described, reinforcing the urgent need for new effective treatments. The present study aimed to evaluate the effects of fendiona and its derivatives, Cu-fendiona and Ag-fendiona, alone and combined with the carbapenems meropenem (MPM) and imipenem (IMP) in different Kp-KPC strains, in vitro and in the model of Galleria mellonella. For this purpose, we investigated: (i) the minimum inhibitory concentrations (MIC) and minimum bacterial concentrations (MBC) of the compounds; (ii) the effects of combining the compounds with MPM and IMP by checkerboard assay and time-kill method; and (iii) the effect of synergistic combinations on the in vivo model of G. mellonella. The results obtained by MIC and MBC determination demonstrated good antimicrobial activity by the three compounds against all 46 strains. The mean MIC values of fendione, Cu-fendione and Ag-fendione were 42.06, 9.88, and 10.10μg/mL, respectively. Combinations of the compounds with MPM and IMP were tested by checkerboard assay on 9 nonclonally related strains, and no indifferent or antagonistic effects were observed in any of the six combinations tested. Higher synergism rates were obtained by the combinations containing MPM, being this effect detected in 66.67%, 77.78%, and 33.33% of the strains when in association with fendione, Cu-fendione and Agfendione, respectively. Combinations of MPM with Cu-fendione and Ag-fendione were tested by time-kill method on 2 non-clonally related strains. Combinations containing ½ x MIC of each agent have been demonstrate to produce synergistic effect, verified between 9 and 12 hours of activity. It was observed that the combination of MPM with the compound Ag-fendione was able to eradicate the inoculum (106 CFU/mL) applied in the test. Acute toxicity levels of fendione and its derivatives have been evaluated in the G. mellonella model, and the results was considered satisfactory with respect to the use of these compounds alone or in combination. The efficacy of the combinations was also evaluated in vivo in G. mellonella infection model with the same 2 strains used in time-kill method. A statistically significant superiority of the treatment with the combinations over the administration of the agents alone was found. Thus, the results obtained in our study demonstrate the potential of fendione, Cu-fendione and Ag-fendione as drug candidates alone or in combination with carbapenem antimicrobials.