Oral Candidiasis: A Disease of Opportunity

Abstract

Oral candidiasis, commonly referred to as “thrush,” is an opportunistic fungal infection that commonly affects the oral mucosa. The main causative agent, Candida albicans, is a highly versatile commensal organism that is well adapted to its human host; however, changes in the host microenvironment can promote the transition from one of commensalism to pathogen. This transition is heavily reliant on an impressive repertoire of virulence factors, most notably cell surface adhesins, proteolytic enzymes, morphologic switching, and the development of drug resistance. In the oral cavity, the co-adhesion of C. albicans with bacteria is crucial for its persistence, and a wide range of synergistic interactions with various oral species were described to enhance colonization in the host. As a frequent colonizer of the oral mucosa, the host immune response in the oral cavity is oriented toward a more tolerogenic state and, therefore, local innate immune defenses play a central role in maintaining Candida in its commensal state. Specifically, in addition to preventing Candida adherence to epithelial cells, saliva is enriched with anti-candidal peptides, considered to be part of the host innate immunity. The T helper 17 (Th17)-type adaptive immune response is mainly involved in mucosal host defenses, controlling initial growth of Candida and inhibiting subsequent tissue invasion. Animal models, most notably the mouse model of oropharyngeal candidiasis and the rat model of denture stomatitis, are instrumental in our understanding of Candida virulence factors and the factors leading to host susceptibility to infections. Given the continuing rise in development of resistance to the limited number of traditional antifungal agents, novel therapeutic strategies are directed toward identifying bioactive compounds that target pathogenic mechanisms to prevent C. albicans transition from harmless commensal to pathogen.

In Vitro and In Vivo Inhibitory Activity of Limonene against Different Isolates of Candida spp.

“…Candidiasis, caused by the opportunistic fungus Candida albicans , is one of the most prevalent infections that affect humans and can display severe morbidity in immunosuppressed individuals [ 1 ]. In fact, hospitalized patients infected with HIV/AIDS (human immunodeficiency virus/Acquired immunodeficiency syndrome) or chronic obstructive pulmonary disease or undergoing chemotherapy treatments and transplant patients represent the most relevant groups at risk of developing Oropharyngeal Candidiasis (OPC) [ 2 , 3 ].…”

Comparative Evaluations of the Pathogenesis of Candida auris Phenotypes and Candida albicans Using Clinically Relevant Murine Models of Infections

“… C. albicans is a common colonizer of the oral mucosal surfaces and the causative agent of oral candidiasis ( 43 , 44 ); however, the ability of C. auris to adhere and colonize oral mucosal tissue has not been investigated. Using a modification of our established mouse model ( 45 ), we performed comparative time course studies to monitor colonization and disease development over time.…”

Bio- and Nanotechnology as the Key for Clinical Application of Salivary Peptide Histatin: A Necessary Advance

“…Candida albicans is a diploid polymorphic fungus that can switch between the yeast and hyphal growth modes and exists as a common member of the human microflora, asymptomatically colonizing the skin and the gastrointestinal, respiratory and genitourinary tracts as a commensal microorganism [11,12]. The commensal state of C. albicans is maintained by some factors as intact epithelial barriers, innate immune system responses and coexisting microflora, but in situations in which these factors are absent or weakened, C. albicans proliferation is favored and this fungus can become an opportunistic microorganism, progressing from superficial infections to systemic infections that can lead to death [12,13]. Risk factors for Candida spp.…”