Some problems associated with the identification of Corynebacterium equi

Characterization of human clinical isolates of Dietzia species previously misidentified as Rhodococcus equi

“…It is also recognized as an opportunistic pathogen of humans, particularly in human immunodeficiency virus (HIV)-infected immunocompromised persons [1,2]. The traditional identification of R. equi in clinical laboratories is usually performed by the characterization of colony and microscopic morphology, and biochemical tests using a commercial kit such as the API Coryne [3][4][5]. However, the battery of traditional tests is not always sufficient for the accurate identification of R. equi because of its potential variation of colony and microscopic morphology or biochemical inactivity [3,4].…”

“…The traditional identification of R. equi in clinical laboratories is usually performed by the characterization of colony and microscopic morphology, and biochemical tests using a commercial kit such as the API Coryne [3][4][5]. However, the battery of traditional tests is not always sufficient for the accurate identification of R. equi because of its potential variation of colony and microscopic morphology or biochemical inactivity [3,4]. For instance, Bemer-Melchior et al [6] reported that API Coryne gave an identification of R. equi for a Dietzia maris isolate obtained from an immunocompromised patient.…”

Equi factors in the identification of Corynebacterium equi Magnusson

“…The organism is usually identified on the basis of the source of isolation, the characteristic mucoid-teardrop colony, the delicate salmon-pink color which often develops with time, catalase activity, urea hydrolysis, and failure to produce acid from carbohydrates (1, 8), but some isolates sent to our laboratory as C. equi by these criteria have not been C. equi. A recent report on variation in C. equi colony morphology showed that a small proportion of isolates did not develop the classical mucoid appearance and consequently might not be recognized as C. equi (8).…”

“…The finding that all isolates produced catalase and failed to ferment dextrose and xylose was consistent with the results of most other workers (1, 8). Other investigators have also found that a few strains hydrolyze esculin and that the majority of strains hydrolyze urea (8). There is disagreement as to the hydrolysis of hippurate.…”

“…The other 79 isolates came from the collection of J. B. Woolcock and M. D. Mutimer, University of Queensland, Australia (8). They belonged to the following serotypes: 1 (41), 2 (16), 3 (1), 5 (5), 6 (15), and 7 (1).…”