Assessment of technique for rapid detection of Escherichia coli and Proteus species in urine by head-space gas-liquid chromatography

Abstract

A test depending on the production of ethanol by Escherichia coli from lactose and dimethyl disulfide by Proteus spp. from methionine in the early exponential phase of growth and the detection of these products by head-space gas-liquid chromatography has been applied to 75 specimens of urine selected to provide the most stringent trial of the test. The test was found to be rapid and reliable for the commonest findings in the microbiological examination of urine. In 3 to 4 h it detected "significant" numbers (greater than 10(5)/ml) of E. coli or of Proteus mirabilis or P. inconstans A, identified as Proteus spp., in 23 urines. It recorded the absence of infection from 32 urines containing borderline or "not significant" numbers of any organism. Significant numbers of other organisms in 13 urines were not mistaken for E. coli or Proteus spp. However, the test was less successful for some less common findings. Klebsiella ozenae in significant numbers in one urine was mistaken for E. coli. P. morganii in significant numbers in one urine was not detected. E. coli or P. mirabilis mixed with significant numbers of another organism were not detected in four out of five urines. The technique is simple and could be automated. It appears to merit more extensive trial in a hospital laboratory and further development to detect and correctly identify more species that cause urinary tract infections.