[Comparative activity in vitro of ceftizoxime, ceftazidime and imipenem against Acinetobacter calcoaceticus]

Acinetobacter calcoaceticus, a nosocomial pathogenic agent, is isolated with increasing frequency from hospitalized patients. Acinetobacter is one of the most resistant pathogens to currently available antibiotics, particularly beta-lactam antibiotics. Beta-lactamases (TEM penicillinase and cephalosporinase) and problems of permeability are the most frequent mechanisms of resistance. The authors compared the in vitro activity of ceftizoxim, ceftazidim and imipenem against 82 clinical isolates of Acinetobacter calcoaceticus. Ceftizoxim, structurally similar to cefotaxim, was highly active in vitro; MIC 50%, 90% and geometric mean were respectively 6.28, 15 and 6.9 micrograms/ml. A significant difference was observed between the anitratum and lwoffi varieties. The lwoffi variety was more susceptible to tested drugs than the anitratum variety. Ceftazidim activity was comparable with MIC 50 of 6.5 micrograms/ml and MIC 90 of 26.2 micrograms/ml. A good bactericidal activity was observed against susceptible strains (MIC less than or equal to 4 micrograms/ml). Imipenem showed the greatest activity since 0.47 microgram/ml of the drug inhibited 90% of Acinetobacter calcoaceticus.