Sensitivities of indole-positive klebsiella to various β-lactam antibiotics

Indole-positive strains of Klebsiella are classified into Klebsiella oxytoca and K. planticola in Bergey's Manual (1984 ed.). We studied the sensitivities of clinical isolates of these two Klebsiella species to ampicillin (ABPC), piperacillin (PIPC), cephaloridine (CER), cefoperazone (CPZ), latamoxef (LMOX), and aztreonam (AZT). The results were as follows. 1. Forty-eight strains of 246 indole-positive Klebsiella isolated in eleven general hospitals were identified as K. planticola. 2. The sensitivity distribution of K. planticola to β-lactam antibiotics was similar to that of K. pneumoniae rather than to K. oxytoca. 3. The β-lactamase of K. planticola was identified as penicillinase from its substrate specificity. 4. AZT, a monobactam antibiotic, showed a high degree of antibacterial activity to K. oxytoca as well as to K. pneumoniae and to K. planticola. 5. AZT was not hydrolyzed by either the β-lactamase of K. planticola or that of K. oxytoca. 6. The β-lactamase of K. oxytoca was identified as a cephalosporinase from its substrate specificity. The present results indicate that K. planticola should be carefully differentiated from K. oxytoca in clinical laboratories.