Distribution of β-lactamases and phenotype analysis in clinical strains of Acinetobacter calcoaceticus

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Abstract
One hundred clinical strains of Acinetobacter calcoaceticus isolated from 1981 to 1986 were screened for enzymatic resistance to β-lactam antibiotics. Fourteen β-antibiotics were tested and four phenotypes were defined on the basis of enzymatic resistance and of susceptibility to the following β-lactams: ticarcillin, piperacillin, cefotaxime, and ceftazidime. The resistance of A. calcoaceticus to β-lactam antibiotics was predominantly due to β-lactamases, which were produced by 81% of the strains. In most (71%) of the β-lactamase producing strains, a penicillinase of the TEM type was observed; in 9% of the strains, all isolated since 1985, a CARB-type penicillinase with a pI 6·3 was observed. The presence of a cephalosporinase type enzyme was detected in acinetobacter strains isolated since 1981 and its incidence increased in 1986. Multiple β-lactamases (penicillinase plus cephalosporinase) were observed in 32% of the strains.