Though the most well known and written about Candida species is Candida Albicans there are actually around 150 known species of Candida, a group of fungi that live on most humans and can also be picked up from things they touch, foods they eat, and especially hospitals. Most Candida species are commensals which means they are microorganisms that live in the body without causing any harm. They prefer typical places that a fungus likes to live, warm, damp and dark areas and are mostly found in the intestines and respiratory tracts.
Any infection caused by a candida species of fungus is referred to as Candidemia or Candidiasis. For immunocompromised people these infections are life threatening as they can enter the blood stream and cause a systemic infection where internal organs are attacked, but they can also occur in otherwise healthy people as the result of several triggers that lead to an overgrowth of the Candida species such as prolonged use of antibiotics, uncontrolled diabetes and so on.
Here is a summary of 9 of the Candida species.
Candida species 1 – Albicans
The most capable of causing disease are Candida Albicans and are the cause of over half of all cases of Candidiasis. They live on membranes such as the mouth, throat, genitals and intestines. The majority of articles written about yeast infections presume them to be an Albicans based infection.
Candida species 2 – Glabrata
These are the next most pathogenic candida species causing 15 to 20 % of all cases of Candidiasis. Glabrata and Albicans are the cause of 80% of invasive candidiasis cases between them. Glabrata is more resistant to some forms of anti-fungal drugs making it harder to treat than Albicans. For further information see related articles.
Candida species 3 – Parapsilosis
Responsible for 10 to 20% of all candidiasis cases. Parapsilosis is notable for its cause of sepsis and other wound and tissue infections in patients with compromised immune systems. It is not a Candida that sticks with just humans and has been found on animals in the soil and in insects. Out of all fungi this one is often found on human hands. Patients at risk from this candida species are those with compromised immune systems and patients undergoing surgery particularly stomach surgery. Treatment is usually that of a systemic anti-fungal such as Amphotericin B or fluconazole.
Candida species 4 – Tropicalis
This candida species is the cause of 6 to 12 % of all candidiasis cases. Patients with diabetes, lymphoma and leukaemia are more susceptible to septicaemia caused by Candida Tropicalis. It is part of the normal flora a human carries and like Albicans, overgrowth triggers the problems. However unlike Albicans it is not linked to mucosal superficial infections, rather it causes deep infections.
Candida species 5 – Krusei
The cause of 1 to 3% of all cases of candidiasis and resistant to many anti-fungal drugs including fluconazole. It is found mostly in patients with haematological malignancies and patients who are immunocompromised. Mortality is higher with this candida species. Interestingly it is used in chocolate production! It is part of the fermentation process to get rid of the bitter taste of cocoa beans and break them down.
Candida species 6,7,8 – Kefyr, Guilliermondii and Lusitaniae
Together the cause of less than 5% of all candidiasis cases. Lusitaniae is noteworthy as it too is resistant to many anti-fungal treatments including amphotericin B. Between 1979 and 1990 less then 30 cases of Candida Lusitaniae were reported but it is now on the rise with those undertaking bone marrow transplants and cancer patients taking chemotherapy being most at risk. Kefyr was once known as Candida pseudotropicalia and has been isolated from nails. As well as being found on human skin the candida species Guilliermondii can be found in leather, sea water, buttermilk, fish, animal faeces and beer.
Candida species 9 – Dubliniensis
Noted for causing infection in HIV patients. It is very closely related to the Albicans candida species and for some time was often mistaken for Albicans. For example in a European study of 2589 Candida cases, that were all originally labelled as Albicans caused, it was found when re-examined that 52 (2%) were actually Dubliniensis. It can be treated by amphotericin B, itraconazole and ketoconazole. Though initially sensitive to fluconazole further testing has found this candida species seems to be quickly developing a resistance to this anti-fungal treatment, especially in patients taking long term treatment.