Evaluation of 36 Minitek tests and a new approach for identification of nonfermenters

Abstract

Thirty-six Minitek (BBL Microbiology Systems, Cockeysville, Md.) tests were evaluated with 625 Kansai Medical University stock strains of 22 species and one group of nonfermentative gram-negative rods able to grow on ordinary peptone media. Among the 36 tests, 15 were selected because a clear-cut reaction was shown by all 625 Kansai Medical University strains. Of these 15 tests, 12 were further selected for routine use because they were regarded as useful for the identification of nonfermenters. The 12 tests were arranged into the following four groups: (i) lysine-arginine-ornithine, (ii) urea-ortho-nitrophenyl-beta-D-galactopyranoside-dextrose aerobic, (iii) maltose-xylose-starch, and (iv) esculin-nitrate reduction-indole. A new profile system for four digits, the Minitek Y-Y (Yabuuchi and Yamanaka) system, consisting of 64 numbers which represent each single species and 11 numbers which give two to four species, is herein proposed. The system was designed primarily for a less expensive identification of gram-negative rods already confirmed in a butt of either triple sugar iron or Kligler iron agar for their lack of ability to ferment dextrose. Among the 539 clinical isolates obtained from 3 hospitals, 511 strains identifiable by classical methods were also identified by the Minitek Y-Y system.