HSBTE DMLT Medically important fungi Candida and Dermatophytes. Immunology and Mycology. IVth Semester. Unit III.

Medically important fungi - Candida, Dermatophytes.

Candida

Candida is a genus of yeast fungi that has various species. some of them cause infections in humans. Candida albicans is a medically important Candida that causes thrush, vaginitis, and chronic mucocutaneous candidiasis.

General characteristics:

1. Morphology: Candida albicans exist as unicellular yeast cells but can also form multicellular structures such as pseudohyphae and true hyphae. The yeast cells are oval to round in shape, ranging from 2 to 10 micrometers in size.

2. Habitat: Candida albicans is part of the normal microbial flora present on mucous membranes and skin surfaces of humans’ gastrointestinal tract, mouth, and female genital tract.

3. Temperature Sensitivity: Candida albicans shows temperature-dependent growth. An optimal temperature for growth is between 25 to 37 degrees Celsius.

4. Energy: Candida albicans is a facultative anaerobe. It is capable of growing in both aerobic and anaerobic conditions. It obtains energy through the fermentation of glucose.

5. Pathogenicity: Candida albicans is an opportunistic pathogen. It causes infections when host immunity is low or when there are disruptions in the normal microbial flora. It is capable of causing various forms of candidiasis, including oral thrush, vulvovaginal candidiasis, cutaneous candidiasis, and invasive candidiasis.

6. Virulence factor: Candida albicans possesses numerous virulence factors that contribute to its pathogenicity. These are adhesion molecules facilitating attachment to host cells and tissues, secretion of hydrolytic enzymes (e.g., proteases, phospholipases) promoting tissue invasion, and the ability to form biofilms on surfaces.

7. Laboratory diagnosis: Budding yeast and pseudohyphae are visible microscopically in the tissue sample. Inoculation of the sample in culture media and its incubation at 25 to 37 degrees C shows the growth of yeast. Chlamydospores are formed by the Candida albicans but not by the other candida species.

Candida is a genus of fungi that includes various species. Some of these species are medically important due to their ability to cause infections in humans. Candida infections are called candidiasis. It ranges from superficial mucocutaneous infections to more serious systemic infections. It can affect various parts of the body, including the mouth, throat, genitals, and bloodstream. It's important to note that while Candida is a normal part of the body's microbial flora, overgrowth or infection can occur under certain conditions.

Candida Species

· Candida albicans: The most common species responsible for the majority of Candida infections. It naturally resides in the human gastrointestinal and genitourinary tracts. However, overgrowth can lead to infections.

· Other Candida Species (Non Candida albican species): In addition to C. albicans, other species such as Candida glabrata, Candida tropicalis, Candida krusei, and Candida parapsilosis can also cause infections.

Common Infections

· Oral Thrush: It is commonly known as Oropharyngeal Candidiasis (OPC). It affects the mouth and throat. It affects infants, the elderly, or individuals with weakened immune systems.

· Genital Candidiasis: Commonly known as a yeast infection, affecting the genital area in both men and women.

· Invasive Candidiasis: Serious infections that can affect the bloodstream, organs, and other internal tissues. It is often seen in immunocompromised individuals.

Risk Factors

• · Weakened Immune System: Conditions such as HIV/AIDS, cancer, or immunosuppressive medications increase the risk.

• · Diabetes: Poorly controlled diabetes can create an environment conducive to Candida overgrowth.

• · Antibiotic Use: Disruption of the normal microbial balance in the body can lead to Candida overgrowth.

Symptoms

• · Symptoms depend on the type and location of the infection but may include itching, burning, discharge, and discomfort.

• · Invasive candidiasis symptoms can be more severe and include fever, chills, and organ dysfunction.

Prevention

• · Proper hygiene, especially in the genital area, helps to prevent yeast infections.

• · Topical or oral antifungal agents may be prescribed for localized infections.

• · Managing conditions such as diabetes and avoiding the use of unnecessary antibiotics reduce the risk of Candida overgrowth.

Medically important fungi - Dermatophytes

Dermatophytes are a group of fungi that infections of the skin, hair, and nails. These infections are collectively known as dermatophytosis or tinea infections. Dermatophytes can infect and survive on keratinized tissues, such as the skin, hair, and nails, because they can utilize keratin as a nutrient source.

Classification: Dermatophytes belong to three genera: Trichophyton, Microsporum, and Epidermophyton. Each genus includes different species that may cause specific types of infections.

Mode of Infection: Dermatophytes typically infect the outer layers of the skin, nails, and hair. They can be transmitted from person to person, from animals to humans, or through contact with contaminated surfaces like floors in public places such as swimming pools, locker rooms, or showers.

Types of Infections

• 1. Tinea Capitis: Infection of the scalp and hair.

• 2. Tinea Corporis: Infection of the body (excluding the scalp, beard, and groin).

• 3. Tinea Cruris: Infection of the groin area (jock itch).

• 4. Tinea Pedis: Infection of the feet (athlete's foot).

• 5. Tinea Unguium: Infection of the nails.

Symptoms: Dermatophyte infections can cause redness, itching, scaling, and sometimes blistering of the affected area. Discoloration and thickening of the nails may occur in nail infections.

Treatment: Both topical and oral antifungal medications are commonly used to treat dermatophyte infections. Topical creams or ointments are often effective for mild cases, while more severe or widespread infections may require oral antifungal medications.

Prevention: Good hygiene practices, such as keeping the skin clean and dry, wearing breathable clothing, and avoiding sharing personal items like towels and razors, can help prevent dermatophyte infections.

Dr Pramila Singh