What is a Yeast Infection and Candida?

Yeast infection is a fungus infection of the skin or mucous membranes caused by a group of yeast-like fungi called Candida. Yeast are organisms that multiply by budding. Candida is one of the normal organisms that live in the body and it frequently colonizes the skin and mucous membranes of the respiratory, intestinal, genital and urinary tracts without causing harm. Colonization in the mouth and pharynx is found in 30-55% of healthy young adults, and Candida species may be detected in 40-65% of feces.

When the body changes its normal bacterial makeup (normal flora), or its defense system does not function properly, Candida can begin to multiply more and become harmful to certain areas of the body, creating an infection. If the infection travels to the blood stream, a Systemic Yeast Infection can result.

Who can get a Candida Infection?

Three of every 4 women have at least 1 bout of Vulvovaginal Candidiasis (VVC) during their lifetime. In addition, Candida are frequently recovered from the hospital environment, including foods, countertops, air-conditiong vents, floors, respirators, and medical personnel.

Increasing amounts of critically ill people are being treated for chronic conditions in the hospital, making them susceptible to a yeast infection caused by Candida. High-risk areas for Candida infection include neonatal, pediatric, and adult ICUs, both medical and surgical. Candida species are the most common cause of fungal infection affecting immunocompromised patients.

In HIV-positive persons who are not receiving Antiretroviral therapy, more than 90% experience Oropharyngeal Candidiasis and 10% have at least 1 episode of esophageal candidiasis. In persons with systemic infections, Candida species are now the fourth most commonly isolated pathogens from blood cultures.

How Candida manifests itself?

Clinical and autopsy studies have confirmed the marked increase in the incidence of disseminated Candidiasis, reflecting a parallel increase in the frequency of Candidemia. This increase is due to an increased recognition of the fungus, a growing population of patients at risk (ie, patients undergoing complex surgical procedures, patients with indwelling vascular devices), and the improved survival of patients with underlying neoplasms or collagen-vascular disease and patients who are immunosuppressed.

Similar rates of Mucocutaneous and Systemic Candidiasis have been observed worldwide. In fact, throughout the world, Candida species have replaced Cryptococcus species as the most common fungal pathogens affecting immunocompromised hosts.

The most common species that affect humans is Candida albicans (C. albicans). About 50-60% of yeast infections are caused by C. albicans.

C. glabrata is the second most common species, causing 15-20% of infections; followed by and C. parapsilosis (10-20%), C. tropicalis (6-12%) C. krusei accounts for 1-3%.

C. glabrata and C. albicans account for approximately 70-80% of yeast isolated from patients with invasive candidiasis.

C. glabrata and C. krusei are important because they are resistant to some antifungal medicines.

C tropicalis has been considered an important cause of Candidemia in patients with cancer (leukemia) and in those who have undergone bone marrow transplantation.Our body has the natural ability to fight against organisms, including Candida.

However, when these host defense mechanisms become defected, yeast infections can result. For example:

(1) Intact Mucocutaneous barriers : Skin is the body's largest organ and the first line of defense against organisms such as bacteria, fungi, and viruses. Wounds, intravenous catheters, burns, and ulcerations are breaks in the skin's barrier to allow infections to quickly gain access to the body.

(2) Protection from other bacterial flora : Candida is not the only species that is naturally found in the body. There are some species that colonize the mouth and help to keep the numbers of Candida at a manageable level. These are what are sometimes called the "good" bacteria. However when the population numbers change through antibiotics, and kill the "good bacteria". This set is favorable for Candida, which can take over and multiply rapidly, creating a yeast infection.

(3) Cellular response : The body normally has specialized cells that make up the immunity system. A few of them are phagocytes, monocytes, complement cells, immunoglobulins, T cells and white cells (leukocytes). Diabetes mellitus, HIV, cancer, leukemia are are all conditions where the cellular response is malfunctioned and the risk is increased for a yeast infection

Candida species also contain their own set of well-recognized virulence factors. Although not well characterized, several virulence factors may contribute to their ability to cause infection.

The main virulence factors are surface molecules that permit adherence of the organism to other structures (eg, human cells, extracellular matrix, prosthetic devices), acid proteases, and the ability to convert to a hyphal form.

What does an Yeast Infection look like?

A yeast infection can have several appearances:

• Candida infection of the mouth (Thrush, or Oral Candidiasis) has an appearance of white flecks on the tongue, upper roof of the mouth, or the pharynx.
  
• Vaginal candidasis has a white, thick, curd-like appearance.
  
• On the skin, in some cases, a Candida infection appears as itchy, red lesions with pustules and a distinct border with surrounding satellite lesions.