C albicans Commensal and Pathogen

Candida albicans is commonly found in the gastrointestinal tract, oral cavity, and genital area as a harmless commensal. Based on recent studies in healthy individuals, asymptomatic oral carriage of Candida species is estimated to occur in 24-70% of children and adults, with a reduced frequency in babies less than 1 year of age (Table 5.1). Of isolates identified, the majority are C. albicans (38-76% in adults and children). Again, the frequency of C. albicans differs across different age groups, with a far greater proportion of isolates identified as C. albicans in young babies and in the elderly (Table 5.1). Higher oral carriage rates are found in HIV positive patients (Sanchez-Vargas et al., 2005a; Liu et al., 2006) and diabetics (Belazi et al., 2005).

Asymptomatic vaginal carriage of Candida species is estimated to occur in 21-32% of healthy women, with C. albicans representing 20-98% of identified isolates (Agatensi et al., 1991; Holland et al., 2003; Beigi et al., 2004; Beltrame et al., 2006; Pirotta & Garland, 2006). One recent study found that within a group of women repeatedly screened over 12 months 30% were never colonised, 70% were colonised on at least 1 occasion, and 4% were persistently colonised (Beigi et al., 2004). Higher rates of vaginal carriage have been found in pregnant women, women colonised by Lactobacillus species (Cotch et al., 1998; Beigi et al., 2004), Type I diabetics (de Leon et al., 2002), and post-antibiotic treatment (Pirotta & Garland, 2006).

It is important, however, to note that as well as being a harmless commensal C. albicans, and some other Candida species, are opportunistic pathogens and cause a range of different infections. These cover a spectrum ranging from irritating superficial mucosal lesions to disseminated blood infections, which have an associated high mortality rate.

K. Kavanagh (ed.), New Insights in Medical Mycology. © Springer 2007

Table 5.1 Oral carriage of Candida, and specifically C. albicans, in the general population. Carriage frequency of yeasts in the oral cavity of asymptomatic individuals are mean values calculated from the percentage carriage rates reported in recent studies. The range of reported values is shown below the mean value

% Carriage Age group (year) (range)

% Isolates C. albicans (range)

Source references

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Kleinegger et al. (1996),

Qi et al. (2005) Kleinegger et al. (1996), Qi et al. (2005), Sanchez-Vargas et al. (2005a, b) Kleinegger et al. (1996), Fanello et al. (2001), Qi et al. (2005), Sanchez-Vargas et al., (2005a, b) Kleinegger et al. (1996), Wang et al. (2006b)

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