[In vitro activity of ceftazidime compared with five beta-lactamase stable compounds against clinical strains of Acinetobacter calcoaceticus ].

Acinetobacter calcoaceticus is recognized as one of the most resistant nosocomial pathogens. Clinical isolates of Acinetobacter are usually resistant to most beta-lactam antibiotics. The objective of this study was to evaluate the in vitro activity of ceftazidime, a new broad spectrum highly potent beta-lactam antibiotic, able to inhibit especially Pseudomonas and Providencia. Its activity against 96 clinical strains of Acinetobacter was compared with the activity of 5 recent beta-lactam antibiotics which are resistant to beta-lactamase degradation (cefoxitine, Cefotaxime, moxalactam, cefotiam, cefamandole). The results of this comparative study of the in vitro activity of the 6 beta-lactam antibiotics exhibit a higher activity of ceftazidime: 50 p. cent of the strains were inhibited at a concentration of 4 micrograms/ml while the other drugs inhibited 50 p. cent of the strains at concentrations superior to 10 micrograms/ml; the geometric mean was 7 micrograms/ml for ceftazidime while for the other drugs it was more than 10 micrograms/ml and for 3 of them, the geometric mean was more than 40 micrograms/ml. Otherwise one could notice a bimodal distribution of the strains which suggests the presence of 2 populations of Acinetobacter, respectively inhibited with 4 micrograms/ml (susceptible) and 64 or 128 micrograms/ml (resistant). Finally this study shows that ceftazidime is one of the most active compounds against clinical isolates of Acinetobacter calcoaceticus among the 3rd generation of cephalosporins.