Jen Cihlar, DO, Vanderbilt University Medical Center
In vitro and in animal model studies demonstrate synergistic bactericidal activity of amoxicillin and cefdinir without rise in resistance of either agent when used together. An interesting finding, but this combination needs significantly more research before clinical application.
The authors identified the synergistic potential of amoxicillin and cefdinir as part of drug screening process for FDA-approved drugs in part of a process to identify agents capable of reversing MRSA beta-lactam resistance. In vitro studies found the fractional inhibitory concentration index (FICI) for 14 representative prevalent MRSA strains to be 0.5 indicating synergistic effect across multiple strains. Time-kill assays of a community acquired MRSA strain (CA-MRSA) and a hospital acquired MRSA strain (HA-MRSA) found bactericidal activity with >3 log10 reduction after 24hrs and found no increase in MIC of either antibiotic when used in combination. In vivo Galleria mellonella larvae infection model using pediatric dosing concentration equivalents, demonstrated a 67% survival rate for the CA-MRSA strain and an 82% survival rate for the HA-MRSA strain after 7 days from a dual single dose, which was comparable to the efficacy of vancomycin used in this model. Overall, these are some promising findings warranting much further investigation as a viable treatment option for MRSA.
Reference: Altarawneh H, Alhomra T, Alharbi M, Fan Y, Derrick JP, Xia G. Synergistic bactericidal activity of a novel dual β-lactam combination against methicillin-resistant Staphylococcus aureus. J Antimicrob Chemother. 2024;79(7):1677-1682. doi:10.1093/jac/dkae165