ABSTRACT
INTRODUCTION: The auxanographic carbohydrate assimilation had been an important method for differentiation of yeasts. Prevailing methods described in the literature for carbohydrate assimilation has limited scope for use in large scale yeast identification. AIM: To optimize the large scale auxanographic carbohydrate assimilation method for yeast identification. MATERIALS AND METHODS: A modified auxanographic carbohydrate assimilation method was developed and a total of 35 isolates of Candida species comprising of four ATCC (American Type Culture Collection) Candida strains (Candida albicans ATCC 90028, Candida tropicalis ATCC 90018, Candida parapsilosis ATCC 750, Candida krusei ATCC 6258) and 31 clinical isolates of Candida tropicalis (n=13), Candida krusei (n=7), Candida glabrata (n=3), Candida kefyr (n=3), Candida albicans (n=5) were validated. The carbohydrates tested were Glucose, Sucrose, Maltose, Lactose, Cellubiose, Raffinose, Trehalose, Xylose, Galactose and Dulcitol. RESULTS: A total of 35 Candida species were tested for their carbohydrate assimilative property and the results were consistent with the existing standard protocols. A well circumscribed opaque yeast growth indicated assimilation of the test carbohydrate and translucent to opalescent growth with the outline of initial inoculum alone indicated lack of assimilation. The control plate indicated no growth of the Candida species. CONCLUSION: The carbohydrate assimilation tests finds utility for yeast diversity studies exploring novel ecological niches. The technique described here facilitates testing of an extended range of carbohydrates and yeasts in a cost effective manner.
ABSTRACT
INTRODUCTION: Candida species are normal inhabitants of the skin and mucosa. The importance of epidemiological monitoring of yeasts involved in pathogenic processes is unquestionable due to the increase of these infections over the last decade; MATERIALS AND METHODS: The clinical samples from the respiratory tract (sputum, bronchial wash, tracheal secretions), saliva, blood, urine, middle ear discharge, vitreous fluid, corneal ulcer, and plastic devices (endotracheal tube, catheter tip, suction tip) were collected and cultured. The species of Candida isolated were identified. RESULTS: A total of 111 isolates of Candida species were recovered from 250 diverse clinical sources. C. albicans (39.64%) was the most isolated species, although the Candida non albicans species with 60.36% showed the major prevalence. In blood cultures, C. krusei (38.23%) and C. albicans (20.58%) were isolated frequently. C. albicans (63.27%) was the predominant species in mucosal surface. Urinary tract infections caused by yeasts were more frequent in hospitalized patients, C. krusei (50.0%) being commonly isolated, followed by C. albicans (25.0%). DISCUSSION: Several virulence factors like, biofilm, proteinase, phospholipase, etc. contribute to the pathogenecity. Early detection of virulence factors by Candida is useful in clinical decision making. We therefore have aimed at demonstrating the formation of biofilm using the method proposed by Branchini et al, (1994). The proteinase produced by Candida was estimated as per the method of Staib et al, (1965). Phospholipase assay was carried out as per the method of Samaranayake et al, (2005). CONCLUSIONS: The data suggests that the capacity of Candida species to produce biofilm may be a reflection of the pathogenic potential of the isolates. C. krusei and C. tropicalis showed strong slime production. The non-Candida albicans produced more proteinase than C. albicans. C. albicans produced higher levels of phospholipase than non Candida albicans in this study.
