Fungal Pathogens Flashcards
What are fungi?
- Separate kingdom of organisms - Eukaryotic microorganisms
What are the 2 major fungal growth modes?
- Yeast cells = yeast 2. Hypha (moulds)
Is yeast single or multicellular? Hyphae?
Yeast = single-celled Hyphae = multicellular
How do fungi reproduce?
Reproduce asexually and/or sexually, spore formation
What are the 3 main life styles of fungi?
- Saprophytes 2. Plant pathogens 3. Animal pathogens
What are saprophytes?
a plant, fungus, or microorganism that lives on dead or decaying organic matter.
What are the 3 types of fungal disease?
- Superficial infection 2. Subcutaneous infection 3. Systemic infection
What do superficial infections affect?
skin, hair, nails and mucocutaneous tissue
What do subcutaneous infections affect?
affecting subcutaneous tissue, usually following traumatic implantation
What do systemic infections affect?
Deep-seated organs
Dermatophytes:
- Mould or yeast?
- What type of infections do they cause?
- What do they require for growth?
- Mould
- Superficial (skin, hair, nail)
- Keratin
Where do dermatophytes originate?
Soil, other animals or other humans
How are dermatophytes classified?
In terms of where they originate from
If dermatophytes come from: a) soil b) other animals c) other humans what are they called?
a) geophilic b) zoophilic c) anthropophilic
Disease name (medical AND colloquial) for dermatophyte infections according to their site:
What is the prefix?
a) foot skin
b) nail (toe or finger)
c) groin area skin
d) limbs and torso skin generally
e) scalp skin and hair
Prefix is tinea-
a) tinea pedis –> athletes foot
b) tinea unguium –> fungal nail disease
c) tinea cruris –> jock itch
d) tinea corporis –> ringworm
e) tinea capitis –> scalp ringworm
How common are fungal nail infections?
common in the general adult population, probably 5-25% rate, increasing incidence in elderly people
Who is athletes foot seen mostly in?
more common than onychomycosis, more common in adults (not younger people) and sportsmen
Who is scalp ringworm most common among?
most common among prepubertal children.
Signs and symptoms of atheletes foot
- Uni- or bilateral,
- Itching, flaking, fissuring of skin
- Plantar: Soles of feet dry and scaly, if skin of whole of foot affected “Moccasin foot”
- Hyperhidrosis, secondary to infection may increase severity
- May spread to infect toe nails
Which organism typically causes atheletes foot?
Dermatophyte –> ‘trichophyton rubrum’
What are the 4 main types of fungal nail infection (tinea unguium)?
Thickening, discolouring, dystrophy:
- Lateral/distal subungual
- Superficial white – usually in immunocompromised
- Proximal nail edge
- Total nail dystrophy
Which organisms typically cause tinea unguium (fungal nail infection)?
Trichophyton rubrum and T. interdigitale (both dermatophytes)
Who is tinea cruris (jock itch) seen more in?
More prevalent in men than women
Signs and symptoms of tinea cruris (jock itch)?
- More prevalent in men than women
- Itching, scaling, erythematous plaques with distinct edges
- Satellite lesions sometimes present
- May extend to buttocks, back and lower abdomen
Which organism typically causes tinea cruris (jock itch)?
T. rubrum (dermatophyte)
Signs and symptoms of tinea capitis (scalp ringworm)?
- Signs range from: slight inflammation, scaly patches, with alopecia, “black dots”, “grey patches” to severe inflammation
- In areas of severe inflammation you can get Kerion celsi
What are Kerion celsi? What does it look like? What type of dermatophytes has usually caused this?
- A severe inflammatory form of tinea capitis that is characterised by a T-cell-mediated hypersensitivity reaction against dermatophyte fungi.
- Boggy, inflamed lesions, usually from zoophilic dermatophytes
Typical scalp ringworn in baby
Typical presentation of tinea corporis (ringworm)?
- Circular, single or multiple erythematous plaques
- May extend from e.g. scalp or groin
- Invasion of follicle “Majocci’s granuloma”
Which organisms typically cause tinea corporis (ringworm)?
Typical cause, wide range of dermatophytes, anthropophilic or zoophilic
Investigation of dermatophyte infections?
Microscopy and culture
In non severe cases, how would dermatophyte infections be treated? What medications can be used for this?
- Topical antifungal therapy: mild disease (self diagnosis and treatment)
- Terbinafine, clotrimazole, miconazole
How are severe cases of dermatophyte infection treated?
Systemic antifungal therapy
What should ALL cases of tinea capitis be treated with? Why?
Systemic oral antifungals as topical therapy will NOT be curative (only has role in reducing spread)
Which drugs are used in the treatment of systemic fungal infections?
- Griseofulvin, terbinafine, itraconazole (depends on causal species)
Malassezia:
a) Mould or yeast?
b) Where is it naturally found?
c) 3 examples?
d) What diseases does it have a role in?
a) Genus of yeats
b) Part of normal skin flora in all humans from shortly after birth - highest levels on head and trunk
c) M. sympodialis, M. restricta and M. globosa
d) Pityriasis versicolor, seborrhoeic dermatitis and atopic eczema
What is Pityriasis versicolor? What is it caused by?
- A common fungal infection that causes small patches of skin to become scaly and discoloured
- Caused by Malassezia.
Typical presentation of pityriasis versicolor?
- Hyper- or hypopigmented lesions (mainly on upper trunk)
- Between puberty and middle age
- More common in tropics
- Relapsing disease
Diagnosis of pityriasis versicolorvia microscopy?
- Yeast cells and hyphal segments “Sphagetti and meatballs”
- Culture difficult and not interpretable
Treatment of pityriasis versicolor?
- Topical antifungals e.g. clotrimazole
- If fails, oral antifungals e.g. fluconazole or itraconazole
Candida:
- Yeast or mould?
- Where is it normally found?
- What type of infections can it cause?
- 4 examples of species?
- Large genus of yeasts
- Often colonises the mucosal sufaces and GI tract in healthy people
- Cause of superficial mucosal (oral and vaginal) disease “thrush”, also occasionally skin disease and keratitis
- Cause of systemic disease, once present in circulatory system, can infect almost any organ in the body
–Candida albicans
–Candida glabrata
–Candida parapsilosis
–Candida krusei
Candida can cause superficial infection of the oral mucosa. What are the 4 types?
- Acute pseudo-membranous
- Chronic atrophic
- Angular cheilitis
- Chronic hypoplastic
What is acute pseudomembranous candidiasis? Who is it typically seen in?
- A classic form of oral candidiasis, commonly referred to as thrush
- Typically seen in:
- those with a low CD4 count (AIDS patients NOT on treatment)
- younger patients
- asthma with steroid inhalers
What is chronic atrophic candidiasis? Who is it typically seen in?
- Erythema (redness of the skin or mucous membranes - seen in infection)
- Typically seen in older patients
What is angular cheilitis?
- Inflammation of corners of mouth
What is chronic hyperplastic candiasis? What is it characterised by?
- A variant of oral candidiasis
- Lesions may undergo malignant transformation
Which patients is oral candidosis most commonly seen in?
- HIV/AIDS
- Antibiotic use
- Head and neck cancer
- General debiliation in hospitalised patients
Why is oral candidosis more commonly seen in HIV/AIDS patients?
Sometimes even with anti-retroviral therapy, T-cell immunity is important to prevent mucosal candidosis
Why can antibiotic use lead to oral candidosis?
Suppresses normal bacterial flora –> less competition for yeasts
Why can head and neck cancer patients lead to oral candidosis?
Radiotherapy and chemotherapy affects salivary secretions which would otherwise suppress candida infection
Why can general debilitation in hospitalised patients lead to oral candidosis?
Increases colonisation and risk of oral disease
What is candida vulvovaginitis?
Candidiasis in the vagina –> vaginal yeast infection
Typical presentation of candida vulvovaginitis?
- Pruritis, burning sensation, +/- discharge
- Inflammation of vaginal epithelium, may extend to labia majora
- Often more florid infections during pregnancy
- Often recurring
Treatment of superficial candidosis?
- Usually oral azoles –> fluconazole highly effective
- Resistance in normally sensitive species (e.g. Candida albicans) or naturally resistant species (Candida krusei) can be problem
Why should you NOT use oral fluconazole or other azoles in pregnant women? What should you use instead?
this increases risk of teratologies (e.g. heart defects), use topical azoles eg clotrimazole
Candida can infect almost any organ in the body. How is it defined?
Usually by site of infection
How is systemic candidosis usually acquired?
From colonised skin or mucosal sites, or from GI tract (usually seem in the compromised host)
Which is the most common species of Candida?
Candida albicans
What is candida oesophagitis? Who is it seen in?
- Candidiasis in the oesophagus
- Mainly in HIV
- In 10-20% patients with oropharyngeal disease
- Pain/difficulty on eating/swallowing
- Diagnosed by endoscopy with biopsy
What is candidaemia? How should it be treated?
- Presence of candida in blood culture
- Start antifungal therapy
- Remove lines (where possible)
- Check eyes and heart
- For endocarditis and endophthalmitis
Candidaemia can lead to occular candidosis. What are the 2 forms of this?
Candida chorioentinitis and endophthalmitis
What is candida endocarditis? Who is it seen in?
- A rare consequence of candidaemia
- IV drug users
- Valve surgery –> vegetations seen on heart valves
Typical presentation of candida endocarditis?
Fever, weight loss, fatigue, heart murmur
How are urinary tract Candida infections caused?
Ascending from genital tract infection/colonisation or from catheterisation
Who are urinary tract Candida infections more common in?
Women, diabetics, damaged/abnormal urinary tracts, ICU patients
What is candida peritonitis?
- Complication of peritoneal dialysis
- Can be caused by perforation of bowl during surgery
- Fever, abdominal pain, nausea, vomiting
Treatment of systemic candidosis?
–Depends on Candida sp. sensitivity, severity, need for oral agent
–Echinocandins, e.g. Anidulafungin (IV)
–Azoles, e.g. Fluconazole (oral)
–Liposomal Amphotericin B (IV)
Aspergillus:
- yeast or mould?
- common form of exposure?
- Genus of moulds - filamentous fungi producing airborne spores
- Exposure to Aspergillus spores universal by inhalation
- Airways may be colonised by Aspergillus sp. (doesn’t always mean infection)
What are 4 medically important species of Aspergillus?
–Aspergillus fumigatus (most common)
–Aspergillus niger
–Aspergillus flavus
–Aspergillus terreus
What is aspergillosis?
- Reaction to inhaled Aspergillus
- Infection usually affect the respiratory system
In cavities (e.g. lungs), what can aspergillus cause?
An aspergilloma is a clump of mold which exists in a body cavity such as a paranasal sinus or an organ such as the lung. By definition, it is caused by fungi of the genus Aspergillus.
In patients with asthma or CF, what can aspergillus cause?
Allergic reaction:
- Allergic bronchopulmonary aspergillosis
- allergic sinus disease
Aspergillosis can become a chronic infection. What lung disease can this cause?
Chronic pulmonary aspergillosis
Aspergillosis can lead to an invasive infections especially in immunocompromised patients. What can this lead to?
Invasive pulmonary aspergillosis, invasive aspergillus sinusitis
Which patients can develop cavities in their lungs which can, in turn, lead to aspergilloma?
Patients with cavities from previous tuberculosis, sarcoid, surgery
Aspergillomas are often indolent, but what can they cause if they break up?
Haemoptysis and are potentially fatal
What is the most common form of allergic aspergillosis?
Allergic Bronchopulmonary aspergillosis
How does allergic Bronchopulmonary aspergillosis typically present? How is IgE affected?
- Wheezing
- breathlessness
- loss of lung function
- bronchiectasis
- Airways inflammation
Raised total IgE
Specific IgE and G reaction to Aspergillus
How is allergic Bronchopulmonary aspergillosis treated?
Responds to steroids, sometimes antifungal therapy added
Who is most prone to developing chronic pulmonary aspergillosis?
Patients with COPD
How does chronic pulmonary aspergillosis typically present?
Chronic respiratory symptoms, cough, wheezing, breathlessness, chest pain
Who is invasive aspergillosis most commonly seen in?
Patients with haematological malignancy, stem cell and solid organ transplant –> low neutrophil counts
How does invasive aspergillosis spread?
- Angioinvasion of lung tissue
- Dissemination in c. 25% of cases to extrapulmonary sites
What is present in chest CT of invasive aspergillosis?
Halo and air crescent signs on chest CT
What is the prognosis for invasive aspergillosis?
Moderate to poor prognosis, even with aggressive antifungal therapy
Treatment for aspergilloma?
Resection
Treatment for allergic aspergillosis?
Steroids +/- antifungals
Treatment for chronic pulmonary aspergillosis and invasive aspergillosis?
Antifungals; itraconazole, amphotercin B
What does this picture show?
Pityriasis versicolor –> characteristic small round yeast cells combined with short sections of hyphae (grapes + bananas)
This is an aspergilloma (cavity filled with fungal ball). What is most likely to have formed the original cavity?
tuberculosis
Who is most likely to present with tinea capitis?
Prepubescent children
Which kinds of patients present with this form of oral candidosis? What is this form?
- Erythematous form
- Mainly seen in older patients
Which is the best antifungal for urinary tract candidosis?
a) itraconazole
b) terbinafine
c) fluconazole
d) caspofungin
e) voriconazole
Fluconazole
5 yr old male, background of CF, raised total IgE, Aspergillus specific IgE and IgG, mucous plugging in lungs, wheeze.
Diagnosis?
Allergic bronchopulmonary aspergillosis
In what context is the following sign seen?
Candidaemia –> can lead to occular candidosis
Where might this tinea cruris lesion have spread from?
Feet - tinea pedis
Name this fungus
Aspergillus fumigatus (the spores shedding off the head are what we inhale)
