Differential Susceptibility of Indole-Positive and -Negative Strains of Klebsiella pneumoniae to Cefazolin, Chloramphenicol and Tetracycline

Abstract

Biochemical properties and antibiotic susceptibilities of 168 clinical isolates of K. pneumoniae were tested. On the basis of the indole reaction, 30 isolates (18%) were indole-positive and 138 isolates (82%) were indole-negative. A significant difference to antibiotic susceptibility was found in each of the 2 groups of isolates. Of the indole-negative isolates, 82.6% were susceptible to cefazolin at 6.25 .mu.g/ml or lower, while the indole-positive isolates varied in susceptibility to cefazolin. All of the indole-positive isolates were suceptible to chloramphenicol and tetracycline, but the indole-negative isolates varied in their susceptibility to these antibiotics. Whereas there was no relationship between indole production and susceptibility to cephalothin among the K. pneumoniae isolates studied, it appeared that there was a correlation between the indole reaction and susceptibility to cefazolin, chloramphenicol and tetracycline.