Reproducibility of biotypes using enterotubes

Using both stock and clinical isolates, the Enterotube system was examined for reproducibility of its biotype identification. Fifty stock strains of Enterobacteriaceae were tested on each of 22 separate days (interrun evaluation), and ten Enterotubes per strain were inoculated from one subculture (intrarun evaluation). It was found that 2 of the 50 strains (4 percent) demonstrated reproducibility of biotypes, defined as no variation in the results of the 22 interrun Enterotubes. Twenty-one of the 50 strains (42 percent) demonstrated reproducibility of biotypes, defined as no variation in the results of the ten intrarun Enterotubes. In addition, 20 replicate Enterotube biotype identifications were performed on each of 114 urine cultures which had greater than 10(5) morphologically identical colonies per milliliter of urine. Forty-two of these 114 clinical urine cultures (34 percent) demonstrated no variation in biochemical test results with the 20 replicate Enterotubes. In 47 (44 percent) of the 20 replicate urine cultures, one biochemical test result varied. Two or more biochemical test results were different in the 20 Enterotubes from 25 (22 percent) of the urine cultures.