Effectiveness and Nephrotoxicity of Loading Dose Colistin–Meropenem versus Loading Dose Colistin–Imipenem in the Treatment of Carbapenem-Resistant Acinetobacter baumannii Infection

Carbapenem-resistant Acinetobacter baumannii (CRAB) is becoming more widely recognized as a serious cause of nosocomial infections, and colistin has been reintroduced in recent years for the treatment of CRAB infection. Combinations of colistin and meropenem or imipenem have been found to be effective against CRAB isolates, whereas clinical investigations have not definitively demonstrated the theoretical benefits of colistin combined therapy in patients with CRAB infections. The objective of this study was to compare the primary outcome (30-day survival rate) and secondary outcomes (clinical response, microbiological response and nephrotoxicity) between patients who received loading dose (LD) colistin−meropenem and LD colistin−imipenem for the treatment of CRAB infection. A retrospective cohort analysis was performed at Chiang Mai University Hospital in patients with CRAB infection who received LD colistin−meropenem or LD colistin−imipenem between 2011 and 2017, and 379 patients fulfilled the requirements for the inclusion criteria. The results of this study showed that patients who received LD colistin−imipenem had a lower 30-day survival rate (adjusted HR = 0.57, 95% CI: 0.37−0.90; p = 0.015) and a lower clinical response (aHR = 0.56, 95% CI: 0.35−0.90; p = 0.017) compared with those who received LD colistin−meropenem. The microbiological response in patients with LD colistin−imipenem was 0.52 times (aHR) lower than that in those who received colistin−meropenem (95% CI: 0.34−0.81; p = 0.004); however, there was no significant difference in nephrotoxicity (aHR = 1.03, 95% CI: 0.67−1.57; p = 0.897) between the two combination regimens. In conclusion, when comparing the combination of LD colistin with imipenem or meropenem, the combination of LD colistin and meropenem provides a better survival rate for treating CRAB. Thus, we suggest that combinations of LD colistin and meropenem should be considered when treating CRAB infections.