Differentiation of Klebsiella-Enterobacter (Aerobacter)-Serratia by biochemical tests and antibiotic susceptibility.

Studies were undertaken for the differentiation of members of the Klebsiella-Enterobacter (Aerobacter)-Serratia division by biochemical tests and antibiotic susceptibility. A total of 67 cultures were tested. Strain identification was readily accomplished with the use of motility tests and arabinose fermentation. In addition, a practical schema, based on sensitivity pattern, proved valuable in the classification of the different strains. Most (if not all) Klebsiella strains were susceptible to cephalothin, and all were sensitive to colistin. Enterobacter strains were resistant to cephalothin but susceptible to colistin. In contrast to those other members of the group, all Serratia strains were resistant to both cephalothin and colistin. The combination of a limited number of biochemical reactions and single-disc sensitivity tests appears to be a logical approach for the tentative identification of Klebsiella-Enterobacter (Aerobacter)-Serratia strains.