In-vitro activity of cephalosporins alone and combined with sulbactam against various strains of Acinetobacter baumannii with different antibiotic resistance profiles.

The beta-lactamases of six strains of Acinetobacter baumannii were investigated using analytical isoelectric focusing, and the MIC values for 16 beta-lactam antibiotics determined against the strains. Three strains produced a chromosomal cephalosporinase (pI > 8.5), one strain a CARB-5 beta-lactamase (pI = 6.35), one strain a TEM-1 penicillinase (pI = 5.4) as well as a cephalosporinase (pI > 8.5), and one carbapenem-resistant strain a beta-lactamase with a pI > 8.5. Ceftazidime, cefepime, cefpirome, imipenem and meropenem were found to be the most effective beta-lactams against five strains. Sulbactam was active against four of the strains at 1-4 mg/L and showed enhanced killing effects with cefpirome.