Synergistic activities between carbapenems and other antimicrobial agents against Acinetobacter baumannii including multidrug-resistant and extensively drug-resistant isolates

Treatment options for multidrug-resistant (MDR) and extensively drug-resistant (XDR) Acinetobacter baumannii have been seriously limited and may require combination antimicrobial therapy. In this study, we searched for synergistic activity between carbapenems (doripenem, imipenem and meropenem) and various non-traditional agents (cefoperazone/sulbactam, doxycycline, rifampicin, netilmicin and moxifloxacin) against 40 A. baumannii clinical isolates, including MDR and XDR isolates. The results showed that combination of each carbapenem with cefoperazone/sulbactam, based on the Etest method, demonstrated synergy more frequently (17.5–32.5%) than the other tested agents, which may suggest a role in combination therapy against highly resistant A. baumannii.