Korty-eight clinical strains that were tentatively identified as Corynebacterium minutissimum on the basis of standard biochemical reactions (Hollis-Weaver tables) as well as by the use of the API (RAPID) Coryne system were examined further. Two different groups of strains were observed. The first group (including the type strain of C minutissimum) contained 27 strains showing creamy colonies. These strains grew homogeneously in 6.5% NaCl broth, exhibited DNase activity, were susceptible to the vibriocidal compound O/l 29, produced succinic acid, and contained mycolic acids. The second group comprised 21 strains with dry colonies. They grew in clumps at the surface of 6.5% NaCl broth, DNase activity was not detected, they were resistant It is generally believed that the identification of coryneform bacteria (ie, asporogenous, irregular gram-positive rods) is one of the most difficult tasks for the clinical microbiologist. The reason for this is two-fold: (1) the group of coryneform bacteria is extremely heterogeneous; 1 and (2) there are very few identification systems for coryneform bacteria, and their databases cover only a certain proportion of this large group of bacteria.
" 4Corynebacterium minutissimum is considered to be one of the more frequently encountered true Corynebacterium species in clinical specimens. Originally, it was thought that C minutissimum caused erythrasma, but later studies questioned this disease association and revealed that erythrasma is probably a polymicrobial process. ' Since 1990, the Department of Medical Microbiology at the University of Zurich (DMMZ) has isolated or received many clinically significant strains tentatively identified as C minutissimum. As a cursory review of these strains indicated that they were rather heterogeneous we decided to characterize them further. Heterogeneity within C minutisssimum strains was also reported by Hollis and Weaver who divided C minutissimum isolates into two groups corresponding to strains NCTC 10288 (ATCC 23348) (sucrose fermenting) and ATCC 23346 (sucrose nonfermenting).5 By applying phenotypical, chemotaxonomical and molecular methods, we could demonstrate that a large proportion of strains identified as C minutissimum actually correspond to C amycolatum.
MATERIALS AND METHODS
StrainsThe clinical strains used in this study were cultured from clinical materials using standard procedures or were referred to the DMMZ for identification between 1990 and 1995. Some strains were also received from 378 Downloaded from https://academic.oup.