Inhibitory effects of oral Actinomyces on the proliferation, virulence and biofilm formation of Candida albicans

Abstract

ObjectiveThe pathogenesis of Candida-associated stomatitis involves the dysfunction of flora antagonistic to Candida. Oral Actinomyces species play an important role in regulating the oral microecological balance. The objective of this study was to investigate the antagonism of three oral Actinomyces against Candida albicans. DesignSuspensions, culture supernatants and bacterial lysates of Actinomyces viscosus, Actinomyces naeslundii and Actinomyces odontolyticus were investigated for their actions upon C. albicans. In addition to a commercial strain, six clinical strains of C. albicans were also tested. The proliferation of C. albicans was assessed using a liquid co-cultivation assay. The adhesion, acid protease and extracellular phospholipase activity, hyphae growth, and biofilm formation of C. albicans were measured. ResultsThe results showed that the suspensions, culture supernatants and cell lysates of 108 colony forming units/ml oral Actinomyces significantly inhibited the proliferation of C. albicans (all P<0.001). The culture supernatants exhibited significant antagonistic interactions in terms of adhesion (A. viscosus P<0.001, A. naeslundii P=0.016 and A. odontolyticus P=0.009), acid protease (A. viscosus P=0.035, A. naeslundii P=0.022, A. odontolyticus P<0.001) and phospholipase activities (A. viscosus P=0.011, A. naeslundii P=0.042, A. odontolyticus P=0.021) of Candida, as well as its hyphae growth (A. viscosus P=0.002, A. naeslundii P=0.008, A. odontolyticus P=0.006). Inhibition of C. albicans biofilm formation was also observed. ConclusionsThis study provides preliminary evidence that oral Actinomyces have inhibitory effects on the proliferation, adhesion, metabolic enzyme activity, hyphae formation and biofilm development of C. albicans.