Common Fungal Infections in Humans, Practice Problems and FAQs

You must have seen advertisements for ointments that cure itchy and flaky skin lesions similar to the one shown in the image below.

Fig: Skin lesion

Do you know what causes these lesions? These kinds of lesions are generally caused by pathogenic fungi. Do you know the medical term used for these fungal skin infections? These are generally termed as mycosis. There are several pathogenic species of fungi which cause diseases in humans, other animals and in plants. In humans, fungal infections mostly affect the skin and these fungi are commonly known as dermatophytes as they grow on skin and feed on the keratin present in it. Lack of hygiene results in colonisation of pathogenic fungi on the skin which further leads to skin diseases.

Are there other environmental factors that might also be responsible for aggravating these diseases? Well, yes there are! Fungi prefer to grow in warm and humid places. Thus, most of these fungal infections are triggered due to lack of hygiene in the summer or rainy season when the air is warm and humid.

Different fungal species cause different infections majorly by growing on the epidermis but sometimes they might also invade inside the body as well. Some of the common fungal diseases are candidiasis, athlete’s foot, ringworm, etc. Let us take a peek into how these infections occur, how they can be prevented, identified and cured.

Table of contents

• Ringworm
• Athlete’s foot
• Candidiasis
• Practice problems
• FAQs

Ringworm

Causative organisms

Three different genera of dermatophytes, Trichophyton, Microsporum and Epidermophyton, are responsible for causing ringworm infections in humans.

Fig: Ringworm causing fungi

Trichophyton generally grows on hair, skin and nails. Microsporum grows on hair and skin and Epidermophyton grows on skin and occasionally in nails.

The tiny skin lesions caused during ringworm are called tinea and based on the body part they affect, they are named as Tinea capitis (ringworm of scalp) and Tinea corporis (ringworm of the body).

Mode of Transmission

Ringworm spreads by fungal spores which are either directly acquired from soil or transferred through direct contact with an infected person, animal or inanimate objects like comb, clothes, towels, etc.

Fig: Modes of transmission of ringworm

Symptoms

The fungi causing ringworm mainly infect the toes, neck, armpits, trunk, groin, scalp, and under the nails in particular. Ringworm is identified by the appearance of circular, red, flaky, itchy, and burning lesions. Heat and moisture due to accumulation of sweat in the summer seasons promotes the growth of these fungi in the skin folds of the groin area and in between the toes.

Fig: Symptoms of ringworm

Diagnosis

Ringworm can be identified by the appearance of such as rash or lesions. The presence of specific genus of fungal filaments can further be identified by scraping the affected epidermis followed by staining and observing under the microscope.

Treatment

Patients are advised to use topical creams, antifungal soaps, and shampoos to treat fungal infections. In severe situations, antifungal medicines are given orally to suppress the fungal growth.

Fig: Medications for treatment of ringworm

Prevention

Ringworm can be prevented by maintaining personal hygiene and keeping the skin folds clean and dry. Not sharing personal items can also help to avoid infection.

Athlete’s Foot

Athlete's foot or Tinea pedis is a fungal infection that affects athletes who wear tight-fitting shoes and engage in a lot of physical activity which causes a lot of sweating.

Fig: Athletes wear tigh fitted shoes are prone to have Athlete's foot

Causative organisms

Athlete's foot is caused by the same genera of dermatophytes that cause ringworm, that is, Trichophyton, Microsporum and Epidermophyton.

Mode of Transmission

Athlete's foot is contagious and spreads through direct contact with an infected person or contaminated objects, such as towels, shoes, mats, rugs, clothes, bed linen, etc.

Infected individuals can spread the infection by walking bare-feet in common spaces such as swimming pools, gym locker rooms, saunas, etc. Scratching the infected parts and then touching other parts of the body can also result in spreading of the infection to those parts.

Fig: Athlete’s foot can be transmitted by walking barefoot in common spaces

Symptoms

The disease can affect one or both feet. The infection can affect any part of the foot but is most commonly seen in the skin in between the toes which appears scaly, cracked or peeling and is extremely itchy.

Fig: Lesions in the skin between the toes

The skin on the bottom of the feet also becomes dry and scaly. The affected areas might appear reddish due to inflammation and may have a burning or stinging sensation. Blisters might also appear.

Fig: Dry and scaly skin at the bottom of the feet

Diagnosis

The disease is usually diagnosed simply by looking at the skin lesions. Further confirmation can be done by scraping the lesions and observing the scraped skin samples under the microscope for the presence of fungal mycelia.

Treatment

Antifungal ointments containing clotrimazole, econazole or ciclopirox can help reduce the infection but if the condition is severe, oral antifungal pills may be prescribed for treatment.

Prevention

Avoiding closed shoes and letting the feet breathe, washing the feet regularly and keeping them clean, changing the shoes and socks frequently, not walking barefoot in common spaces and not sharing shoes, clothes, towels, etc are some of the ways to prevent athlete’s foot infection.

Candidiasis

Causative organisms

Candidiasis is caused by a type of yeast called Candida. The most common species that causes candidiasis in humans is Candida albicans.

Fig: Candida albicans

Candida is normally found on the skin and in the mouth, throat, gut, and vagina. It is an opportunistic pathogen which causes infection when the normal microflora of these regions are removed or when the individual’s immune system is compromised which allows Candida to flourish and establish infection.

There are several types of candidiasis:

• Thrush or oropharyngeal candidiasis
• Genital Yeast Infection or genital candidiasis
• Invasive Candidiasis

Oropharyngeal candidiasis

When the Candida yeast infects the mouth and throat, the infection is called thrush. It mostly occurs in newborns, old people, and people with compromised immune systems. Adults who are being treated for cancer, are diabetic, or are under medications immunity suppressing medications like corticosteroids or wide-spectrum antibiotics are at a high risk of encountering oropharyngeal candidiasis.

Modes of transmission

The yeast can spread due to mouth-to-mouth contact during kissing but it manifests itself when the immunity of the new host is compromised.

Symptoms

Appearance of white or yellow patches inside the mouth, e.g., on the tongue, lips, gums, roof of mouth and inner cheeks is one of the symptoms of this disease. Other symptoms include cracking at the corners of the mouth, soreness and pain in the throat, etc.

Fig: Symptoms of oral thrush

Treatment

Oropharyngeal candidiasis can be treated with antifungal medicines like nystatin, clotrimazole, and fluconazole. Using chlorhexidine (CHX) mouthwash to rinse the mouth also helps to eliminate infection.

Genital candidiasis

This occurs more commonly in women when the pH balance in the vagina is disturbed which can be due to pregnancy, diabetes, birth control pills, antibiotics, use of vaginal sprays, lubricants, or spermicides, etc. Other factors promoting genital candidiasis are weak immunity, wearing tight underwear, bathing suits or workout outfits, etc.

Modes of transmission

The infection can spread during vaginal intercourse.

Symptoms

Symptoms include unbearable itchiness in the vagina, rashes, redness and swelling in the genitals, discomfort during urination and thick curdy discharge from the vagina.

Fig: Symptoms of genital candidiasis in females

Treatment

Use of antifungal suppositories or a single dose of antifungal medicine such as fluconazole can be effective. Frequently occurring infections can be controlled by administering regular doses of antifungal medication over several months.

Invasive candidiasis

When Candida invades the bloodstream, it can travel to the heart, brain, blood, eyes, and bones, causing serious, life-threatening infection. This condition is known as invasive candidiasis.

Modes of transmission

It mostly spreads through medical devices or equipment at hospitals or health care facilities. Diabetes, other yeast infections, a weakened immune system, kidney failure, being on antibiotics or steroids, are some of the factors that increase the risks of encountering invasive candidiasis.

Symptoms

The symptoms include fever and chills which can often be misinterpreted as symptoms of other diseases.

Treatment

Oral or intravenous doses of antifungal medications can be used to treat invasive candidiasis. People who are at higher risk of getting infected are given a series of antifungal medications if they are to get admitted to the hospital or undergo medical procedures.

Practice Problems

Q1. You noticed that your friend has a scaly and dry ring-like patch on his neck which causes intense itching. Can you identify this disease based on this symptom? Also, what treatment would you suggest to your friend for this.
Solution: Scaly and dry ring-like patches are a common symptom of fungal disease such as ringworm. It can be treated by applying topical antifungal creams or oral antifungal medicines.

Q2. Select the wrong statement about ringworm.

A. It spreads through sharing objects such as combs or clothes with affected individuals.
B. It is caused by Trichophyton fungi.
C. It results in the secretion of allergic chemicals such as serotonin.
D. Lesion gets worse with constant scraping.

Solution: Ringworm is caused by three fungal genus Epidermophyton, Trihophyton and Microsporum whose spores spread through sharing things such as clothes, combs or towels with infected individuals. It is characterised by dry and scaly lesions which get worse with itching.

It does not result in the secretion of serotonin. Serotonin is secreted by basophils, a type of white blood cell and is associated with inflammatory reactions. Hence, option c is correct.

Q3. Consider the following statements, and find the ones which are correct?

i) Candidiasis is a fungal infection caused by Candida species, often seen in patients whose immune system is compromised, such as patients with autoimmune diseases, in case of transplants, malignancies or the use of catheters

ii) Most of the infections are hospital-acquired, especially in ICU settings.

a. Only i,
b. Only ii,
c. Both i and ii
d. Neither i nor ii

Solution: Candidiasis is a fungal infection caused by a yeast, Candida albicans, that normally lives on the skin and inside the body like mouth, throat, gut, and vagina. It is an opportunistic pathogen which causes infection when the normal microflora of these regions are removed or when the individual’s immune system is compromised which allows Candida to flourish and establish infection.

People with weak immune systems are more likely to get the infection which may include :

• People living with HIV/AIDS
• Organ transplant patients (E.g., Kidney transplant cases)
• Cancer patients
• Hospitalised patients
• Stem cell transplant patients (E.g., bone marrow transplants)
• People taking medications that weaken the immune system (in autoimmune diseases like rheumatoid arthritis)

Even people staying in hospitals for an injury or an illness can acquire a fungal infection through cuts and wounds in the body, through the burns on the skin, etc. Patients staying in the intensive care unit (ICU) are critically ill or injured and are likely to undergo life-saving procedures that can put them at risk for fungal infections such as candidiasis.

Thus, the correct option is c.

Q4. What are the different ways to prevent an athlete's foot?
Answer: Some of the preventative measures against Athlete’s foot are -

• Avoiding closed shoes and letting the feet breathe
• Washing the feet regularly and keeping them clean
• Changing the shoes and socks frequently
• Not walking barefoot in common spaces
• Not sharing shoes, clothes, towels, etc.

FAQs

Q1. Can pets get a ringworm infection?
Answer: Microsporum canis commonly causes ringworm in pets such as cats and dogs but cats are considered to be more vulnerable. Long-haired breeds of cats and dogs are generally more susceptible to the infection.

Q2. Name a multidrug-resistant type of Candida.
Answer: Candida auris is a multidrug-resistant Candida strain that poses a severe global health risk, notably in the United States. It has the potential to cause serious infections and is easily distributed in healthcare facilities.

Q3. Can other skin conditions be misdiagnosed as ringworm?
Answer: Nummular eczema and granuloma annulare are two skin conditions which develop symptoms similar to that of ringworm and can often be mistaken as the latter. Like ringworm, nummular eczema causes circular patches of dry and scaly skin which is often triggered by bug bites or allergies. Granuloma annulare also causes red ring-like bumps on the skin which can be mistaken for ringworm.

Q4. What is a home remedy for an athlete's foot?
Answer: Pouring hydrogen peroxide or rubbing alcohol over the affected area, using tea tree oil, neem oil, topical application of garlic, taking sea salt baths are some of the commonly used home remedies against athlete’s foot.

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