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Angela has taught college Microbiology and has a doctoral degree in Microbiology.
I was born and grew up during the '80s and I remember the Cold War. It seemed like every nightly news report had a segment about U.S. / Soviet relations. I never really paid much attention to the reports, as I was far more occupied playing with my toys or bugging my older sisters. As a child, I never really grasped the long history and tension that existed between the two superpowers. It didn't sink in how the arms race kept escalating, but no one, thankfully, ever gained the upper hand. The United States and the Soviet Union were able to coexist on Earth precisely because neither could get far enough ahead to take over.
This might seem like an odd intro for a lesson about fungal infections, but the parallels are actually quite appropriate. Simmering on the surface and deep inside your body, a cold war is occurring between your microbes, also known as your microbial flora. Fungi, bacteria, viruses, and protozoa are living on and in you in perfect balance. If you're feeling well, it means no one group has gained the upper hand. But, enjoy the stalemate while it lasts. At any time, conditions can shift, thrusting your flora to the brink of full-scale war.
One major player in this cold war is Candida albicans, a dimorphic fungus capable of causing a variety of diseases in susceptible individuals. Usually referred to as simply Candida, this fungus is normally present in the skin, mouth, vagina, and gastrointestinal tract of healthy people. While colonizing your body, which should be a stable 37 degrees Celsius, Candida exists as a single-celled yeast. When Candida is cultured in a lab setting below body temperature, it grows in filaments, similar to the classic bread mold fungus. This fascinating ability to grow in two different forms is what makes Candida a dimorphic fungus.
Candida doesn't normally cause disease despite it being so widespread within the body, because the other members of the normal flora and your immune system keep it from overgrowing. Candida also plays its own part in the cold war by preventing other microbes from getting ahead. As long as everything remains healthy and conditions don't change, this delicate peace can be maintained.
Most people will never get sick from their resident Candida, but there are several things that can lead to outbreaks. Any illness that impairs the immune system can leave the body in a weakened state, unable to successfully control the growth of Candida and resulting in disease. AIDS patients, cancer patients undergoing chemotherapy, and patients on high doses of corticosteroids are the classic examples of people with chronically suppressed immune systems. Also, anything that disrupts the normal microbial community can lead to illnesses associated with Candida. Antibiotics can disrupt or reduce the bacterial populations in the body, allowing the fungal Candida to overgrow and cause disease.
Candidiasis is any disease caused by the fungus Candida. Causes and symptoms are dependent on the part of the body infected. There are three major body systems impacted by Candidiasis, so we will examine each individually.
Probably the most common place for Candidiasis is in the vagina, causing vulvovaginitis, or inflammation of the vulva and vagina. This is commonly known as a yeast infection. In the U.S. alone, it is estimated that 20 million women will suffer from a Candida-caused yeast infection every year. Anything that disrupts the normal vaginal flora has the potential to lead to a yeast infection. Antibiotics, pregnancy, birth control, tight fitting undergarments, sexual contact, and diabetes are just a few of the possible causes.
There is a diverse, normal, and healthy microbial flora associated with the vagina. One of the most abundant and important members of the vaginal flora is Lactobacillus. Lactobacillus is what is called a lactic acid bacteria, so called because it is able to ferment organic substrates and produce lactic acid.
The lactic acid is released into the vaginal environment, and contributes to keeping the pH of the vagina low. This low pH slows the growth of yeasts, like Candida, protecting against infection. Using antibiotics or otherwise disrupting the normal vaginal flora can decrease the number of Lactobacillus. As the production of lactic acid decreases, the pH increases, allowing Candida populations to explode.
The most common symptoms of vulvovaginitis include itchiness, internal burning pain, redness, swelling, and white, cheesy discharge. Usually these symptoms are sufficient for diagnosis. Attempting to positively identify Candida can be difficult because it is a member of the normal flora and is expected to be present. Treatment is usually considered safe and effective enough that it is employed even if the infection is just suspected to be Candida. There are many over-the-counter medicines, as well as prescriptions, like the antifungal Nystatin, that have been shown to be 80-90% effective at eliminating infections.
Thrush is the illness caused by Candida in the oral cavity. Thrush is characterized by small, white flecks on the mucous membranes of the mouth. These flecks eventually form soft masses that resemble milk curds. The mouth can be painful and it can become difficult to swallow. Thrush is common among newborns, who acquire it from their mother while passing through the vagina during birth.
It is also one of the earliest signs of the development of AIDS in adults. The compromised immune system allows the Candida to flourish in the mouths of HIV patients. Treatment of thrush usually only requires a swish and swallow of a preparation of liquid Nystatin. In patients with compromised immune systems, Chlorhexidine mouthwashes are often used to prevent Candida from causing thrush before symptoms develop.
The last major infection point of Candida is in the gastrointestinal tract. This infection is common with long-term antibiotic use. Antibiotics destroy the normal bacteria in the gut, allowing Candida to overgrow. Stomach pain and diarrhea are the most common symptoms. As far back as the 1950s, doctors have been touting the benefits of eating yogurt containing live bacterial cultures when on antibiotics or before gastrointestinal surgeries to help prevent these Candida infections.
A final thing to mention, on rare occasions, immunocompromised patients can get systemic Candidiasis. The fungus invades the bloodstream, usually during surgeries, spreading to the internal organs. These full body infections are very dangerous, life-threatening, and difficult to treat. Intravenous Amphotericin B is the best treatment option, but when combined with poor immune function, treatment is rarely effective.
Let's review the basics of Candida.
Candida albicans is a dimorphic fungus that is a member of the normal human microbial flora, but can cause disease in susceptible hosts. People with compromised immune function or those on long-term antibiotics can develop Candidiasis. Healthy immune function, and the growth of normal flora, usually keeps Candida populations in balance, preventing illnesses.
When Candidiasis does develop, it usually impacts one of three body systems. Most common is vulvovaginitis, also known as a yeast infection. This usually results from disruption of the normal vaginal microbial flora, due to things like antibiotic usage. Candida overgrowth in the vagina can cause itchiness, redness, and discharge. Over-the-counter medications are usually all that is required to cure most yeast infections.
Candidiasis of the mouth is called thrush. AIDS patients and newborns are the most common groups affected and develop the white, milk-curd-like masses in the mouth, typical of thrush infections. Mouthwashes are the most effective method for preventing and eliminating these infections.
Gastrointestinal candidiasis occurs when antibiotics eliminate the normal gut bacteria, allowing Candida to flourish. The infection can cause stomach pain and diarrhea. Eating yogurt can help maintain the bacterial populations and prevent this infection. More rarely, in patients with compromised immune systems, Candida can enter the bloodstream and affect organs. These infections are notoriously difficult to treat and can be life-threatening.
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Biology 103: Microbiology16 chapters | 156 lessons | 12 flashcard sets
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