Variation in induction of chromosomal beta-lactamase expression in strains of Enterobacter cloacae.

Eight strains of Enterobacter cloacae with varying patterns of susceptibility to beta-lactam antibiotics were studied to compare the inducibility and expression of their beta-lactamase genes. These strains included two isolates from one patient, which differed in their susceptibility to cefamandole. A resistant strain constitutively produced large amounts of beta-lactamase; a sensitive strain produced an inducible beta-lactamase. Study of induction and growth characteristics of all strains revealed that the induction and the expression of inducible beta-lactamase genes may vary considerably among strains of E. cloacae.