Evaluation of germ tube test and in-house biochemical tests against the biomeureux api 20c for speciation of candida

Abstract

Background: Candida species are one of the causers of lower genital tract infections of women. Although Candida albicans is the commonest, other species have emerged yet they are less susceptible to azole antifungals and in addition, their clinical manifestations are the same. Germ tube and In-house biochemical methods have long been used as a reliable method for speciating Candida in resource limited settings. Data on their technical performance is limited and it’s unclear if these methods provide accurate speciation of Candida. This calls for a need for an accurate method in detection of Candida infections given that the clinical manifestation is the same for the implicated species. Aim: To evaluate the technical performance of Germ Tube tests and In-house biochemical methods in identifying Candida species against API 20C (Analytical Profile Index 20 Candida, bioMérieux, Marcy l'Etoile, France). Methods: This was cross sectional study using frozen Candida species previously isolated from HVS specimens from women with suspected Vulvo Vaginal Candidiasis (VVC). 175 isolates were removed from the freezer, sub-cultured and re-identified using In-house Biochemical tests (sugar assimilation and Urease tests), Germ tube and API 20C AUX. The performance of the two tests was analyzed using data analysis software (SPSS) Statistical Package for Social Sciences. Results: Of the 175 isolates recovered at subculture, 136 were Candida species while the 39 isolates were non-Candida species. Of the 136 Candida spp, Candida albicans had 62 isolates while the rest were other Candida species. Sensitivity and specificity of Germ tube test was 66.1% and 46.9% respectively while that of In-house biochemical tests was 66.7% and 61.9% respectively. The overall sensitivity and specificity of individual sugars was 87.9% and 70.8% respectively with a moderate kappa agreement of 0.5898. Conclusion and recommendations: Germ tube test should be performed with other tests and a complete battery of sugars should be used when performing In-house biochemical tests.