Bacterial Identification by Microcalorimetry

Abstract

FORREST¹ and other workers have shown that interesting data regarding bacterial metabolism can be obtained by microcalorimetry of growing cultures. In our investigations into the use of microcalorimetry as a means of differentiating one microbial species from another, we have obtained characteristic profiles for different members of the family Enterobacteriaceae by observing the heat produced during their growth in liquid media. The microcalorimeter (Instrumentation Laboratory, Inc.) used is of an experimental design operating at 37° C and having a response time of approximately 10 min. The long term baseline stability is 2% full scale or 0.8 µcal s⁻¹ ml.⁻¹ over a 14 h measuring period. The profiles are recorded on a conventional 10 inch strip chart recorder with a paper feed of 1 inch h⁻¹. The inocula for the temperature equilibrated test vessel consisted of approximately 500 cells obtained by dilution of a logarithmically growing broth culture.