Chapter 8.6 : Presumptive Identification Tests for Yeasts Isolated on Primary Culture

Abstract:

All of the tests described in this procedure ( Table 8.6–1 ) are considered presumptive because they do not test a characteristic of a species that is unique to that species. Some of the tests do have high specificity values, which would make the test sufficient for the purpose of medical management of some clinical situations (e.g., intertriginous candidiasis due to Candida albicans) but insufficient for others (e.g., fungemia due to C. albicans). Presumptive tests also are generally restricted in the range of the species they identify. The results of two different physiological tests with high specificity for a particular species may be appropriate for identifying the species presumptively. However, there are instances when two different species elicit identical positive reactions in both tests. Mycologists and clinical microbiologists must be aware of these obfuscations. For example, C. albicans, by far the most frequently encountered Candida sp. in the clinical setting, and Candida dubliniensis are both germ tube positive and positive for the enzymes β-galactosaminidase and L-proline aminopeptidase ( 1 ).