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

Objective: The 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 Actinornyces against Candida albicans. Design: Suspensions, culture supernatants and bacterial lysates of Actinornyces viscosus, Actinomyces naeslundii and Actinomyces odontolyticus were investigated for their actions upon 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. Results: The results showed that the suspensions, culture supernatants and cell lysates of 10(8) 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. Conclusions: This 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. (C) 2015 Elsevier Ltd. All rights reserved.