Treatment of pan-drug resistant Acinetobacter baumannii

The objective of this study was to investigate the role of sulbactam in the treatment of pan-drug resistant Acinetobacter baumannii (PDRAB). We studied 89 patients with PDRAB infection treated with different antibiotic regimens. Group A (n = 39) were treated with carbapenem with sulbactam and group B (n = 30) with second and third generation cephalosporins, antipseudomonas penicillins, or fluoroquinolones with aminoglycosides. We also studied the MICs for 48 PDRAB strains by using antimicrobial agents with and without sulbactam. The clinical outcomes of the 2 groups did not differ significantly, either in terms of resolution of infection (25/59, 42% in group A vs 12/30, 40% in group B) or survival (35/59, 59% vs 17/30, 57%). However, the MICs indicated that 16 of the 48 strains were sensitive to imipenem/sulbactam, compared with only 2 of the 48 to imipenem alone. The addition of sulbactam thus reversed the response in 30% (14/46) of strains initially resistant or only intermediate sensitive to imipenem. The MICs for meropenem/sulbactam were in the sensitive range for 8 of 48 strains compared to only 3 of the meropenem alone, indicating an 11% (5/45) reversal rate when sulbactam was added to meropenem. For the 38 isolates initially resistant to both carbapenems alone, imipenem/sulbactam reversed the resistance in 16% (6/38), while meropenem/sulbactam did so in only 3% (1/38). Thus, the carbapenem-sulbactam combinations did not clearly improve clinical outcome, but they did demonstrate lower MICs for the PDRAB strains tested. It may be that aggressive, early treatment of A. baumannii infections with these agents might prevent the emergence of PDRAB strains.