1. A.M. Freydiere 1 and R. Robert 2 1 Hôpital Debrousse, Hospices Civils de Lyon, 2 Parasitologie-Mycologie, Angers, France Rapid Candida glabrata identification with a commercial trehalase-maltase detection test Increasing numbers of immuno-compromised patients and certain current medical and surgical management practices have favoured the emergence of normally commensal yeast species as life-threatening pathogens. These yeasts differ in their antifungal drug susceptibilities, so that rapid species-level identification of yeasts isolated from clinical material is imperative for prompt institution of appropriate antifungal therapy (12), since susceptibility data for the isolate may not be immediately available. Candida glabrata, one of these emerging pathogens (3, 11, 13), is the second-most-commonly-isolated yeast species in clinical laboratories (2, 10) and some strains readily show a reduced susceptibility to several azole antifungal agents and notably to fluconazole. Thus because of its frequency of isolation and decreased susceptibility, laboratories should be able to identify this Candida species rapidly. The GLABRATA RTT ® test (Fumouze Diagnostics, France) based on the ability of C. glabrata to hydrolyse trehalose but not maltose allows the identification within 20 minutes. It uses a glucose-oxidase reaction for the detection of glucose and requires only 4 to 6 colonies. The purpose of this work was (i) to assess the performance of this rapid trehalase test for C. glabrata identification applied to colonies grown on four different mycological isolation media (ii) to compare these performance to those of the strip test previously described by Parant et al. (5, 8, 9) Introduction Material and methods Strains: 125 stock isolates, most commonly encountered in clinical samples and representing a total of 14 yeast species were kept on glass beads at –20°C and passaged through one subculture on Sabouraud agar (bioMerieux) to check for purity. Then they were streaked to single colonies on the four different media including chromogenic and non-chromogenic media and incubated at 32 °C for 24 h. Confirmation of the identification of all isolates tested was done with ID 32C identification strips (bioMérieux Marcy l'Etoile, France). The GLABRATA RTT ® test: Principle, description, methodology and interpretation. Conclusion The GLABRATA RTT ® has been shown to be simple, rapid, and reliable. Due to the low inoculum density required (4 to 6 colonies), it should allow the identification directly from the primary isolation medium. An ideal approach to efficient identification of clinical yeast isolates is the use of preliminary presumptive identifications from a polyvalent chromogenic medium that reduces the need for trehalase testing only to those colonies that did not form the characteristic colours. The GLABRATA RTT is a useful adjunct to the work of the routine medical mycology laboratory. Chromogen C. glabrata colonies H2O2H2O2 H2OH2O O2O2 Oxided chromogen (brown-orange) Glucose Rapid hydrolysis (10 min)) Glucose oxidase Peroxidase REAGENTREAGENT Trehalase Trehalose 1- Principle We thank our technicians for their assitance and A. Frangin for her valuable help in producing this poster. The slightly lower specificity of CandiSelect versus Candida ID concerns mainly Candida famata. As a matter of fact, C. famata strains yield pink colonies on Candida ID, and due to this pink coloration, these strains were excluded as C. glabrata. The GLABRATA RTT ® showed higher sensitivity and specificity than the strip tests described by Parant and al. (5, 9) using commercially supplied glucose oxidase strips moistened with trehalose or maltose solutions and smeared with material taken from a yeast colony with an inoculating loop, for strains grown on CHROMagar Candida. Two reasons might be hypothesised (i) the longer contact time with trehalose with the GLABRATA RTT ® (ii) the formulation of CHROMagar Candida since this medium has recently been reformulated by Becton Dickinson (6). For yeasts isolated on chromogenic media, because some Candida species can be recognised directly, only the non-identifiable colonies need to be tested, reducing handling, reagent consumption, time and cost. For strains grown on Candida ID, CandiSelect and Sabouraud gentamicin chloramphenicol, the results of the GLABRATA RTT ® test were similar to those of the strip test. Table 1. Results of the GLABRATA RTT ® test for 125 yeast strains subcultured on 3 chromogenic media and 1 Sabouraud gentamicin chloramphenicol agar. Table 2. Comparaison of the results GLABRATA RTT ® test with those of the Strip trehalase- maltase test with 107 yeast strains subcultured on Candida ID, CandiSelect and one Sabouraud agar. Results - Discussion 1. Chang H.C., S.N. Leaw, A.H. Huang, T.L. 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References 2 - Description Only Candida glabrata should give positive trehalase and negative maltase results. 1 2 3 4 1 2 34 TREALOSETREALOSE MALTOSEMALTOSE CONTROLCONTROL Four tests per panel and three wells per test * 16 C. tropicalis, 13 C. parapsilosis, 5 C. guilliermondii, 4 C. kruseï, 4 C. inconspicua, 3 C. norvegensis, 3 C. lipolytica, 2 Saccharomyces cerevisiae, 2 C. pelliculosa, 2 C. kefyr 4- Interpretation A brown/orange coloration corresponds to a positive reaction while no coloration corresponds to a negative result. +- Of the 125 isolates tested with the GLABRATA RTT ® test, 107 had been previously tested with the one minute strip trehalase and maltase tests described by Parant and al. (5, 9). The comparison of the results of the GLABRATA RTT ® test and the strip trehalase/maltase test is reported in Table 2. In terms of sensitivity and specificity, the GLABRATA RTT ® gives performance similar to those achieved with longer-duration (i) C. glabrata screening tests (2, 7, 10) and (ii) widely used commercial yeast identification systems such as API20CAUX and Vitek YBC (4). Multiplex PCR methods offers 100% sensitivity and specificity for identification of C. glabrata (1), but are less rapid and more expensive than the GLABRATA RTT ® test. The performance of the GLABRATA RTT ® test for C. glabrata identification applied to colonies grown on four mycological isolation media are reported in Table 1. Acknowledgements * 17 C. tropicalis, 13 C. parapsilosis, 5 C. guilliermondii, 4 C. kruseï, 4 C. inconspicua, 3 C. norvegensis, 3 C. lipolytica, 2 Saccharomyces cerevisiae, 2 C. pelliculosa, 2 C. kefyr, 1 C. utilis 8th ECMM Budapest 25 -27 August 2002 4 to 6 colonies in 100 µl of distilled water CHROMagar CandidaCandida IDCandiSelect Pink colonies White colonies 3- Methodology 25 µl of suspension  12 3 4  10 mn 5 to 10 min 25 µl of reagent am.freydiere@chu-lyon.fr Sabouraud White colonies