Pathogenesis and treatment of oral candidosis

REVIEW ARTICLE æ

Pathogenesis and treatment of oral candidosis
David Williams* and Michael Lewis
School of Dentistry, Cardiff University, United Kingdom

Oral infections caused by yeast of the genus Candida and particularly Candida albicans (oral candidoses) have been recognised throughout recorded history. However, since the 1980s a clear surge of interest and associated research intothese infections have occurred. This has largely been due to an increased incidence of oral candidosis over this period, primarily because of the escalation in HIV-infection and the AIDS epidemic. In addition, changes in medical practice leading to a greater use of invasive clinical procedures and a more widespread use of immunosuppressive therapies have also contributed to the problem. Whilst oralcandidosis has previously been considered to be a disease mainly of the elderly and very young, its occurrence throughout the general population is now recognised. Candida are true ‘opportunistic pathogens’ and only instigate oral infection when there is an underlying predisposing condition in the host. Treatment of these infections has continued (and in some regards continues) to be problematicbecause of the potential toxicity of traditional antifungal agents against host cells. The problem has been compounded by the emergence of Candida species other than C. albicans that have inherent resistance against traditional antifungals. The aim of this review is to give the reader a contemporary overview of oral candidosis, the organisms involved, and the management strategies that are currentlyemployed or could be utilised in the future.
Keywords: oral candidosis; Candida

Received: 3 November 2010; Revised: 3 January 2011; Accepted: 4 January 2011; Published: 28 January 2011

he Candida genus is comprised of over 150 species of asporogenous ‘yeast-like’ fungi. Members of this genus are ubiquitously distributed, persisting as saprophytes in soil and aquatic environments, as wellas colonising several animal reservoirs (1Á3). The majority of Candida species are unable to grow at 378C and are, therefore, not normally associated with human colonisation (4). However several species do persist as commensal microorganisms within humans and these can act as opportunistic pathogens in debilitated individuals (Table 1). Candida albicans is the species most frequently associatedwith normal oral carriage in humans, occurring in the mouths of up to 80% of healthy individuals (13). A change from the harmless commensal existence of Candida to a pathogenic state can occur following alteration of the oral cavity environment to one that favours the growth of Candida. The causes of such changes are the so-called predisposing factors for Candida infection (candidosis) and most oftenthese relate to a weakening of host immune defences (Table 2). Infections caused by Candida are most frequently superficial, occurring on moist mucosal surfaces in individuals suffering with a mild debilitation. In severely immunocompromised patients, infections can be systemic

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and are significant because of their associated high mortality. To highlight this, in intensive care unitpatients the mortality rate for individuals with systemic candidosis is approximately 30Á50% (24). Recent decades have seen a significant increase in the incidence of all forms of candidosis and this reflects changes in medical practice with a greater use of invasive surgical procedures, a more widespread use of immunosuppressive therapies as well as broad-spectrum antibiotics. Key to the increase inoral candidosis has, however, been the escalation of HIV-infection and AIDs (25). The most prevalent Candida species involved in human infection is C. albicans. In oral candidosis, C. albicans generally accounts for around 50% of cases (26, 27) and whilst a similar prevalence of C. albicans occurs in systemic candidosis, in recent years higher incidences of non-C. albicans Candida (NCAC) species...