Rapid identification of Enterobacteriaceae. II. Use of a beta-glucuronidase detecting agar medium (PGUA agar) for the identification of E. coli in primary cultures of urine samples

Abstract

beta-glucuronidase activity is an exclusive characteristic of E. Coli and some shigellae among Enterobacteriaceae and Vibrionaceae. An agar medium (PGUA agar) which permits the detection of bacteria with beta-glucuronidase activity in mixed cultures was evaluated as a primary culture medium for clinical samples of urine. The medium was selective for enterobacteria and yielded significantly higher recoveries than MacConkey agar. Based on the examination of 3,460 urine samples, it was found that the use of the PGUA agar has several advantages over conventional methods: 1) 94% of all E. coli cultures could be identified on the basis of their appearance on the primary plates; 2) The use of the PGUA method did not result in any misidentidications as compared to 1% of cultured misidentified by the conventional procedure; 3) Approximately one-half of the urine samples which contained E. coli as the sole organism could be reported following the reading of primary culture plates; 4) The application of the PGUA medium resulted in a 46% reduction in the cost of media employed and a 67% reduction in the time required for the processing of urine samples.