Coaggregation of Candida dubliniensis with Fusobacterium nucleatum

The binding of microorganisms to each other and oral surfaces contributes t o the progression of microbial infections in the oral cavity.. Candida dubl iniensis, a newly characterized species, has been identified in human immun odeficiency virus-seropositive patients and other immunocompromised individ uals. C, dubliniensis phenotypically resembles Candida albicans in many res pects yet can be identified and differentiated as a unique Candida species by phenotypic and genetic profiles. The purpose of this study was to determ ine oral coaggregation (CoAg) partners of C. dubliniensis and to compare th ese findings with CoAg of C, albicans under the same environmental conditio ns. Fifteen isolates of C. dubliniensis and 40 isolates of C. albicans were tested for their ability to coaggregate with strains of Fusobacterium nucl eatum, Peptostreptococcus micros, Peptostreptococcus magnus, Peptostreptoco ccus anaerobius, Porphromonas gingivalis, and Prevotella intermedia. When C . dubliniensis and C. albicans strains were grown at 37 degrees C on Sabour aud dextrose agar, only C. dubliniensis strains coaggregated with F. nuclea tum ATCC 49256 and no C. albicans strains showed CoAg. However, when the C. dubliniensis and C. albicans strains were grown at 25 or 45 degrees C, bot h C, dubliniensis and C,albicans strains demonstrated CoAg with F. nucleatu m. Heating the C. albicans strains (grown at 37 degrees C) at 85 degrees C for 30 min or treating them with dithiothreitol allowed the C. albicans str ains grown at 37 degrees C to coaggregate with F. nucleatum. CoAg at all gr owth temperatures was inhibited by mannose and alpha-methyl mannoside but n ot by EDTA. or arginine, The CoAg reaction between F. nucleatum and the Can dida species involved a heat-labile component on F. nucleatum and a mannan- containing heat-stable receptor on the Candida species. The CoAg reactions between F. nucleatum and the Candida species may. be important in the colon ization of the yeast in the oral cavity, and the CoAg of C. dubliniensis by F. nucleatum when grown at 37 degrees C provides a rapid, specific, and in expensive means to differentiate C. dubliniensis from C. albicans isolates in the clinical laboratory.