Rhodococcus equi: are phenotypic tests the best method for accurate identification?

Excerpt

Heidari Sureshjani and colleagues recently reported Isolation of Rhodococcus equi from a mule with cutaneous wound (Sureshjani et al. 2014). In this article, they describe the use of phenotypic testing for identification of species. The genus Rhodococcus is one of the actinomycete families and the name of this genus first used by Zopf. Rhodococcus are Gram-positive, partially acid fast, aerobic, and non-motile bacteria (Bell et al. 1998). Identification of Rhodococcus species using conventional methods is difficult, and the results of these methods are not suitable for accurate identification. There is some published evidence that the identification of Rhodococcus and Gordonia from each other is impossible with phenotypic tests (Blanc et al. 2007). CAMP (Christie-Atkins-Munch-Petersen) test is actually a rapid identification phenotypic marker for R. equi, although this test is also positive in other bacteria such as Rhodococcus erythropolis, Rhodococcus rhodochrous, Dietzia spp., and Mycobacterium spp. (Pd et al. 2012). The use of conventional methods with molecular technique such as polymerase chain reaction (using choE gene) is very important and necessary for accurate identification of R. equi (Pd et al. 2012; Krewer et al. 2008; Ladrón et al. 2003). …