Candida albicans (Pathogenesis)

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University of Oklahoma Study Abroad Microbiology in Arezzo, Italy[1]

Scanning electron microscope image of Candida albicans yeast cell. From: Science Photo Library [2]

Etiology/Bacteriology

Taxonomy

| Domain = Eukaryota | Phylum = Ascomycota | Class = Saccharomycetes | Order = Saccharomycetales | Family = Saccharomycetaceae | Genus = Candida | species = albicans

NCBI: Taxonomy Genome: Candida albicans

Description

Candida albicans is an opportunistic fungal pathogen that is responsible for candidiasis in human hosts. C. albicans grow in several different morphological forms, ranging from unicellular budding yeast to true hyphae with parallel-side wall [1]. Typically, C. albicanslive as harmless commensals in the gastrointestinal and genitourinary tract and are found in over 70% of the population. Overgrowth of these organisms, however, will lead to disease, and it usually occurs in immunocompromised individuals, such as HIV-infected victims, transplant recipients, chemotherapy patients, and low birth-weight babies [2]. There are three major forms of disease: oropharyngeal candidiasis, vulvovaginal candidiasis, and invasive candidiasis. Over 75% of women will suffer from a C. albicans infection, usually vulvovaginal candidiasis, in their lifetimes, and 40-50% of them will have additional occurrences(s). Interestingly, C. albicans are the 4th leading cause for nosocomial infections in patients’ bloodstreams. This could result in an extremely life-threatening, systemic infection in hospital patients with a mortality rate of 30% [3]. For oropharyngeal candidiasis, infection occurs in the mouth or throat, and is identified by white plaque growth on oral mucous membranes. Vulvovaginal candidiasis or a “yeast infection” is the overgrowth of C. albicans in the vagina, and results in rash, itchiness, and discharge from the genital region. Lastly, invasive candidiasis occurs when the fungal pathogen enters the bloodstream and can easily spread to organs throughout the body. Invasive candidiasis is best identified when antibiotics fail to cure a patient’s fever [4]. C. albicans infections are usually treatable with fluconazole, while severe infections require amphotericin B.

Pathogenesis

Transmission

Candida albicans is usually transmitted from mother to infant through childbirth, and remains as part of a normal human’s microflora. The overgrowth of C. albicans leads to symptoms of disease, and it occurs when there are imbalances – for example, changes in the normal acidity of the vagina. C. albican infections very rarely spread through sexual intercourse. The typical reservoir for C. albicans is in the normal human microflora, and is not found in animal vectors [5]. People-to-people acquired infections mostly happen in hospital settings where immunocompromised patients acquire the yeast from healthcare workers; studies show about a 40% incident rate [6].

References

1. Sudbery P, Gow N, Berman J. 2004. The distinct morphogenic states of Candida albicans. Trends in Microbiology. 12(7):317-24.

2. Kabir MA, Hussain MA, Ahmad Z. 2012. Candida albicans: A Model Organism for Studying Fungal Pathogens. ISRN Microbiology. 2012: 538694.

3. Pfaller MA, Diekema DJ. 2007. Epidemiology of Invasive Candidiasis: a Persistent Public Health Problem. Virulence. (2): 119–128.

4. Centers for Disease Control and Prevention. Candidiasis. [<http://www.cdc.gov/fungal/diseases/candidiasis/index.html/>].

5. Public Health Agency of Canada. Candida albicans - Material Safety Data Sheets. [<http://www.phac-aspc.gc.ca/lab-bio/res/psds-ftss/msds30e-eng.php>].

6. Fanelloa s, Boucharab JP, Jousseta N, Delbosa V, LeFlohicc AM. 2001. Nosocomial Candida albicans acquisition in a geriatric unit: epidemiology and evidence for person-to-person transmission. Journal of Hospital Infection. 47(1):46-52.

Created by Johnson Ong, a student of Tyrrell Conway at the University of Oklahoma.