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Germs that infect humans

Candida albicans

Candida albicans

© Dennis Kunkel Microscopy, Inc.

Microorganism: the yeast Candida albicans.

Disease: thrush.

Occurrence of the disease

History: descriptions of mouth lesions resembling thrush date back as far as the 1800s. In 1839, Bernard Langenbeck described the microorganism responsible for thrush, the yeast we know today as Candida albicans. The prevalence of candidiases (infections caused by C. albicans) increased once antibiotics began to be widely used for other conditions. This phenomenon is thought to be due to the antibiotics' ability to kill the bacteria that normally inhibit the growth of Candida. Freed from the inhibiting effect of the bacteria, the yeast grows unfettered.

Mechanism of action of the microorganism: Thrush is rather common among newborns, as they have not yet developed a balanced natural microbial flora. Candida albicans may cause many other candidiases, depending on the organ it infects. Vaginitis, for example, is a C. albicans infection.

C. albicans is naturally present in the respiratory tract and mouth of most people, and the vagina of most women. The yeast causes no problem in healthy individuals, as its numbers are controlled by naturally occurring microorganisms. If the natural balance between these microorganisms and Candida is perturbed, the virus may multiply, producing a candidiasis such as thrush.

Symptoms of the disease: small white plaques, usually observed on the tongue and in the mouth.

Incubation period: two to five days.

Contagious period: as long as lesions are present.

Hosts: humans.

Transmission: direct contact with oral, dermal or vaginal secretions or excretions from infected individuals. Transmission may also occur from mother to infant during birth.

Treatment of the disease: nystatin and azole, both taken orally.

Geographical distribution of the microorganism: worldwide.

Prevention: disinfection of beds in nurseries, in order to avoid transmission of thrush from one infant to another.

Vaccine: none.