Methodological aspects of a microidentification technique for the differentiation of coagulase-negative staphylococci...

The increasing number of coagulase-negative staphylococci (CNS) obtained from clinical material requires a biochemical identification on a broad basis in order to get a better determination of the clinical relevance of the single species. The method of differentiation presented is based on an inoculated microtiter plate provided with reagents and indicators which is evaluated by means of a coding system including most variations of the typical enzyme patterns. As a result of 7040 test series with 55 defined strains, a high degree of plausibility and reproducibility of the single reactions was found in 1320 tests under the recommended conditions. The biochemical patterns of 1380 strains taken from the diagnostic routine were established by means of this method. Comparisons with a commercially available system showed a large congruence of the single reactions and the results of identification.