T1-L3: Fungal Pathogens

Question 1

How can we categorise fungal disease?

Answer 1

• Superficial infections - affecting skin, hair, nails and mucocutaneous ( skin and mucous membrane) tissue.
  
  • Subcutaneous infection - affecting subcutaneous tissue, usually following traumatic implantation. These are rare.
  • Systemic infection - affecting deep-seated organs

Question 2

What pathogen causes Tinea unguium?

Answer 2

Fungal Nail Disease (Onychomycosis) - Most commonly caused by Trichophyton rubric and T. interdigital.

It leads to a thickening, discolouring and dystrophy of the nail.

Question 3

What is the cause of Tinea Pedis? How does it present clinically?

Answer 3

Most commonly caused by T. rubric. It is more common that fungal nail disease. It presents with itching, flaking and fissuring of the skin. There is not a lot of inflammation. The plantar surface can become dry and scaly - Moccasin foot. Hyperhidrosis can also become secondary to the infection increasing severity. It can present uni-laterally or bilaterally.

Question 4

Give details of Tinea capitis.

Answer 4

Scalp worm. This is mainly seen in pre-pubescent children with the signs ranging from slight inflammation, scallywag’s patches with alopecia to grey/black dots. It usually arises from zoophilic dermatophytes.

Question 5

What is Tinea cruis?

Answer 5

Jock Itch. Typical cause is T. rubric. It can lead to itching, burning, irritation, scaling and erythematous plaques with distinct edges on the groin, buttocks, lower back and abdomen. It is more prevalent in men than women.

Question 6

What is Tinea corpis?

Answer 6

Ring worm. This is caused by a wide range of dermatophytes both anthrophillic or zoophilic. It leads to circular, single out multiple erythematous plaques and can extend e.g. from the face, neck to the groin (Tinea cruis).

Question 7

How are dermatopathic infections:

(a) Investigated?
(b) Treated?

Answer 7

(a) Microscopy and Culture (or self-diagnosis)
(b) Topical anti-fungals in mild therapy - Terbinafine, Clotrimazole and Micronazole.

In all cases of Tinea capitis treatment with systemic anti-fungals topical therapy is not curative. The anti fungal depends on the causal species. Examples include Griseofulvin, Terbinafine and Itraconazole.

Question 8

Sally aged 7, has recently travelled from the tropics. She presents with hyper-pigmented lesions on her trunk. The diagnosis cannot be done with culture but instead microscopy. She is given topical anti-fungals and discharged. What is the likely pathogen?

Answer 8

Pityrialsis versicolor (tinea versicolor) - harmless fungal infection that causes patches of discoloured skin

Question 9

What is the name of a large genus of fungi that colonise the mucosal surfaces and GI tract if healthy people?

Answer 9

Candida. Translocation can lead to superficial mucosal (oral or vaginal) disease known as thrush. It can also cause skin disease and keratitis; once in the circulatory system it can cause systemic disease and infect any organ.

Question 10

In what group are superficial candida infections common in?

Answer 10

Acute pseudomembranous infection - seen in those with AIDS, younger patients and those on steroid inhalers for asthma.

It is seen in patients with HIV/AIDS sometimes even with anti-retroviral therapy due to the low CD4 count. T-cell immunity is important to prevent mucosal candidiosis. It is also seen in those with frequent antibiotic use as there is less competition for yeast.

Question 11

Give species of common Candida?

Answer 11

• Candida albicans
• Candida glabrata
• Candida parapsilosis
• Candida krusei

Question 12

What fungal infection affects 70-80% of all women at lead once during child rearing years with approximately 10% suffering from recurrent infection?

Answer 12

Candida Vulvovaginitis. It can lead to pain, burning sensation and discharge. There is inflammation of vaginal epithelium which may extend to the labia major. It is often more florid during pregnancy.

Question 13

How are superficial candidiasis infections:

(a) Investigated?
(b) Treated? - Give a contraindication

Answer 13

(a) Clinical diagnosis and empirical therapy (particularly candida vulvovaginitis. Also culture with identification and anti fungal sensitivity testing where appropriate particularly in recurrent disease.

(b) Oral azoles particularly fluconazole which is highly affective. Some species are resistant which can become a problem.
Do not use oral fluconazole or other azoles in pregnant women as this increases the reuse of teratologies. Instead treat with topical azoles such as clotrorimazole.

Question 14

What is the most common cause of systemic candidiasis?

Answer 14

Candida albicans.

Can infect almost any part of the body. Defined by the site of infection. Usually acquired from colonised skin or mucosal sites of from GI tract. This is can occur via lines inserted. Usually seen in a compromised host, but not always.

Question 15

Give examples of systemic candidiasis.

Answer 15

• Candida oesphagitis - They present with a difficulty/pain on eating and swallowing and diagnosed with biopsy. This is mainly seen in patients with HIV.
• Candidaemia
• Candida chorioretinitis and endophthalmitis
• Candida endocarditis - leads to vegetations on the heart valves, fever, weight loss, fatigue and heart murmur. It is seen in 2-3% of candidaemia cases. Also in IV drug users and valves surely patients.
• UTI Candida Infection - Treated with fluconazole
• Candida peritonitis - Complication of peritoneal dialysis. It can also arise as a result of perforation of the bowel during surgery (mixed bacterial/yeast infection).

Question 16

How is systemic candidosis:

(a) Diagnosed?
(b) Treated?

Answer 16

(a) Culture, ideally from a sterile site such a blood or peritoneal fluid. It is also investigated using imaging.
(b) Treatment depends on the candida species used and the severity. they may be a need for an oral agent. Treatments may be echinocandins, azoles or liposomal amphotericin.

Question 17

How does exposure to Apergillus occur?

Answer 17

Inhalation. This means that if you grow if from a respiratory sample, it may not necessarily mean you have an infection. Airways may be colonised by Aspergillus sp., for this reason.

Examples include:
• Aspergillus fumigatus (most common)
• Aspergillus niger
• Aspergillus flavus
• Aspergillus terreus

Question 18

Give an account of Aspergillosis.

Answer 18

This is a reaction to inhalation of Aspergillus. If we are healthy we will dispose of the spores. If you have a cavity in the lungs you can get formation of an Aspergilloma (fungal ball).

Aspergilloma occurs when patients have cavities in their lungs. The fungus then gets in the cavity and grows into a ball. Cavities can grow as a result of:
- Previous tuberculosis
- Sarcoid
- Surgery
Aspergillomas are often indolent (often picked up in passing), but may break up causing haemoptysis and potentially fatal.

Question 19

Give complications of Aspergillosis?

Answer 19

• Asthma or CF can lead to an allergic reaction causing Allergic bronchopulmonary aspergillosis or allergic sinus disease. Due to inflammation you see a high total IgE and specific IgE and IgG reaction to Aspergillus Responds to steroids sometimes antifungals are added.
• If you have a chronic lung infection it can lead to chronic pulmonary aspergillosis.
• An invasive infection, seen in those immunocompromised (such as leukaemia) can get invasive pulmonary aspergillosis or invasive aspergillus sinusitis. Low neutrophil count and this allows the fungus to invade into the blood tissue and disseminate into other areas of the body such as the brain, kidney skin. This occurs in 25% of patients. Prognosis is moderate to poor and it needs to be treated quite aggressively.

Question 20

How is Aspergillosis:

(a) Investigated?
(b) Treated?

Answer 20

(a) Culture, Serology and Imaging

(b) Resection. Allergic aspergillosis is treated with steroids and antifungals.