The minimal inhibitory concentration for sulbactam was not associated with the outcome of infections caused by carbapenem-resistant Acinetobacter sp. treated with ampicillin/sulbactam.

Objective: The objective of this study was to evaluate whether the outcomes of carbapenem-resistant Acinetobacter infections treated with ampicillin/sulbactam were associated with the in vitro susceptibility profiles.

Methods: Twenty-two infections were treated with ampicillin/sulbactam. The median treatment duration was 14 days (range: 3-19 days), and the median daily dose was 9 g (range: 1.5-12 g). The median time between Acinetobacter isolation and treatment was 4 days (range: 0-11 days).

Results: The sulbactam minimal inhibitory concentration (MIC) ranged from 2.0 to 32.0 mg/L, and the MIC was not associated with patient outcome, as 4 of 5 (80%) patients with a resistant infection (MIC≥16), 5 of 10 (50%) patients with intermediate isolates (MIC of 8) and only 1 of 7 (14%) patients with susceptible isolates (MIC ≤4) survived hospitalization.

Conclusion: These findings highlight the need to improve the correlation between in vitro susceptibility tests and clinical outcome.