New assay for measuring cell surface hydrophobicities of Candida dubliniensis and Candida albicans

Hydrophobic interactions, based on cell surface hydrophobicity (CSH), are a mong the many and varied mechanisms of adherence deployed by the pathogenic yeast Candida albicans, Recently it was shown that, unlike C. albicans, C. dubliniensis is a species that exhibits an outer fibrillar layer consisten t with constant CSH, Previously, C. dubliniensis grown at 25 or 37 degreesC was shown to coaggregate with the oral anaerobic bacterium Fusobacterium n ucleatum, C. albicans, however, demonstrated similar coaggregation only whe n hydrophobic or grown at 25 degreesC. This observation implied that coaggr egation of Candida cells with F. nucleatum is associated with a hydrophobic yeast cell surface. To test this hypothesis, 42 C. albicans and 40 C. dubl iniensis clinical isolates, including a C. albicans hydrophobic variant, we re grown at 25 and 37 degreesC and tested with the established hydrophobici ty microsphere assay, which determines CSH levels based on the number of mi crospheres attached to the yeast cells. The coaggregation assay was perform ed in parallel experiments. All C. dubliniensis isolates grown at either te mperature, hydrophobic 25 degreesC-grown C. albicans isolates, and the C. a lbicans hydrophobic variant, unlike the 37 degreesC-hydrophilic C. albicans isolates, exhibited hydrophobic CSH levels with the microsphere assay and simultaneously showed maximum, 4+, coaggregation with F. nucleatum, The par allel results obtained for C. dubliniensis using both assays support the us e of the CoAg assay both as a rapid assay to determine CSH and to different iate between C. dubliniensis and C. albicans.