Fungal Organisms Flashcards
What are the characteristics of fungi?
How do they reproduce?
- eukaryotic organisms
- they range from single-celled to macroscopic (multicellular)
- growth forms are mainly hyphal or yeast
- they have a glucan-chitin cell wall
- they reproduce asexually and/or sexually through spore formation
What are the 3 types of lifestyle of a fungus?
- saprophytes - decay organic matter
- plant pathogens
- animal pathogens (small number)
What are the 3 types of fungal disease?
- superficial infection
- subcutaneous infection
- systemic infection
What is meant by a superficial infection?
What 3 types of organism cause this?
it affects skin, hair, nails and mucosal surfaces
it is caused by:
- dermatophytes
- Malassezia
- Candida
What is meant by subcutaneous infection?
this affects subcutaneous tissue, usually following traumatic implantation
it is common in tropical countries
What is meant by a systemic infection?
What types of organisms cause this?
it affects deep-seated organs
it is caused by:
- Candida
- Aspergillus
What are dermatophytes?
a group of slow growing moulds seen as causes of disease in skin, hair and nails
What are the 3 types of dermatophytes and where do they originate?
geophilic - originate in soil
zoophilic - originate in other animals
anthropophilic - originate in other humans
What is shown in the images?
Trichophyton interdigitale
This is a dermatophyte that occurs between the toes
What are the following dermatophyte infections?
What is the % rate of fungal nail infections?
In which group are they more common?
they are common in the general adult population - probably 5-25% rate
there is an increasing incidence in elderly people
What types of people are most commonly affected by Athlete’s foot?
it is more common in adults (not younger people) and sportsmen as it is acquired from communal changing areas
In which group is scalp ringworm more common?
prepubertal children
What are the typical signs of tinea pedis (Athlete’s foot)?
it is unilateral or bilateral
it features itching, flaking or fisuring of the skin
the soles of the feet are dry and scaly
What is it called if Athlete’s foot affects the whole of the foot?
Moccasin foot
there is a fine scale over the plantar surface of the foot
What symptom may increase the severity of Athlete’s foot?
hyperhidrosis (secondary to infection)
this is excess sweating which may increase severity of infection
What may tinea pedis lead to?
- secondary bacterial infection
- it may spread to infect the toe nails
What organism typically causes Tinea pedis?
Trichopyton rubrum
What characterises tinea unguium?
What is an alternative name for it?
Thickening, discolouring and dystrophy of the nails
It is also known as onychomycosis
What are the 4 types of tinea unguium?
the type depends on where on the nail the infection starts
- lateral/distal subungual
- superficial white (usually in immunocompromised)
- proximal
- total nail dystrophy (takes over the whole nail)
What organisms typically cause tinea unguium?
Trichophyton rubrum
Trichophyton interdigitale
What is tinea cruris?
What are the typical features of it?
itching, scaling, erythematous plaques with distinct edges
the active fungus is present at the edges of the plaque
satellite lesions are sometimes present
What are the typical causes of tinea cruris?
Where is it usually found?
T. rubrum
This can spread from the nails or foot
It is found in the groin region but may extend to the buttocks, back and lower abdomen
Where is tinea capitis usually seen?
What does it look like?
it is mainly seen in pre-pubescent children
it ranges from slight inflammation, scaly patches with alopecia, “black dots”, “grey patches” to severe inflammation
What does severe inflammation in tinea capitis lead to?
Kerion celsi
these are boggy inflamed lesions with hair loss and permanent scarring
usually from zoophilic dermatopytes
What is a more rare result of tinea capitis?
Favus
this is the presence of cup shaped crusts or scutula
What is an alternative name for tinea corporis?
What does it look like?
Ringworm
It involves circular, single or multiple erythematous plaques
It may extend from the scalp or groin
What is it called when tinea corporis invades a hair follicle?
Majocci’s granuloma
What is the typical cause of tinea corporis?
a wide range of dermatophytes
either anthropophilic or zoophilic
What is involved in the investigation of dermatophyte infection?
microscopy and culture
sample can come from a hair follicle, piece of nail or skin scraping etc.
What are the 2 types of treatment for a dermatophyte infection?
Mild disease:
- topical antifungal therapy with terbinafine or clotrimazole
- usually self-diagnosis and treatment
Severe disease:
- systemic antifungal therapy
What should all cases of tinea capitis be treated with?
Why?
systemic antifungals
e.g. griseofulvin, terbinafine, itraconazole
topical therapy has a role in reducing spread but will NOT be curative
What are Malassezia?
Where are they found?
they are a genus of yeasts
they are part of normal skin flora in all humans from shortly after birth
they are most frequent on the head and trunk
What diseases are caused by Malassezia?
- pityriasis versicolor
- they have a role in seborrhoeic dermatitis and atopic eczema
What does pityriasis versicolor look like?
What types of people are usually affected?
hyper- or hypopigmented lesions on the upper trunk
it affects people between puberty and middle age
it is more common in the tropics
Why is pityriasis versicolor relapsing?
it is caused by a commensal organism which is always present on the skin
How is pityriasis versicolor diagnosed?
microscopy
it is a dimorphic fungi so yeast cells and hyphal segments are seen (“spaghetti and meatballs”)
culture is difficult and not interpretable
What is the treatment for pityriasis versicolor?
topical antifungals e.g. clotrimazole
if this fails then oral fluconazole or itraconazole is given
What are Candida?
Where are they usually found?
large genus of yeasts
they often colonise the mucosal surfaces and GI tract in healthy people
What types of diseases can Candida cause?
superficial infections:
- mucosal disease (“thrush”) of the mouth and vagina
- skin disease
- keratitis of the cornea
systemic infections:
- once present in the circulatory system, they can infect almost any organ in the body
What are the 4 types of Candida species?
- candida albicans
- candida glabrata
- candida parapsilosis
- candida krusei
What is shown in this image?
Candida albicans
They are dimorphic fungi
The hyphal form is often seen in infected tissues
What are the 3 types of oral candidiosis?
this is a superficial candida infection of the oral mucosa
- acute pseudo-membranous
- chronic atrophic
- chronic hypoplastic
What types of patients tend to be affected by acute pseudo-membranous oral candidiosis?
- low CD4 count (<200 cells/ul)
- younger patients
- asthma with steroid inhalers
What types of patients tend to be affected by chronic atrophic oral candidiosis?
older patients
this is characterised by erythema and angular cheilitis (in corners of mouth)
What is the risk with chronic hypoplastic oral candidiosis?
the lesions may undergo malignant transformations
What 4 groups of patients tend to be affected by oral candidosis?
- patients with HIV/AIDS
- antibiotic use
- head and neck cancer
- general debilitation in hospitalised patients increases colonisation and risk of oral disease
What does HIV/AIDS patients being affected by oral candidiosis show?
T cell immunity is important in preventing mucosal candidosis
Why are people who take antibiotics and have had head and neck cancer more prone to oral candidosis?
antibiotics supress normal bacterial flora so there is less competition for yeasts
in head and neck cancer, radiotherapy and chemotherapy affect salivary secretions
What % of women are affected by candida vulvovaginitis?
How is it diagnosed?
it affects 70-80% of all women at least once during child-bearing years
10% of women suffer from recurrent vulvovaginal candidosis
it is diagnosed by positive culture in symptomatic patients
What are the symptoms of candida vulvovaginitis?
- pruritis, burning sensation +/- discharge
- inflammation of vaginal epithelium (may extend to labia majora)
infections are often more florid during pregnancy
How is superficial candidosis diagnosed?
- clinical diagnosis and empiric therapy
- culture with identification and antifungal sensitivity testing where appropriate (recurrent disease)
What are the treatments for superficial candidosis?
What is the problem with this?
oral azoles
fluconazole is highly effective
resistance in normally sensitive species (candida albicans) or naturally resistant species (candida krusei) can be a problem
What type of treatment for superficial candidosis should not be used in pregnancy?
oral fluconazole or other azoles
they increase the risk of teratologies (e.g. heart defects)
topical azoles (e.g. clotrimazole) should be used instead
What organs are typically affected by candida spp.?
How are they usually acquired?
candida spp. can infect almost any organ in the body
it is usually acquired from colonised skin or mucosal sites or from the GI tract
How is systemic candidosis identified?
What is it caused by and who does it affect?
disseminated disease can be identified from blood culture
it is most commonly caused by candida albicans
it is usually seen in the compromised host
What patients are most commonly affected by candia oesophagitis?
mainly HIV patients
it is present in 10-20% patients with oropharyngeal disease
How is candida oesophagitis diagnosed?
What symptoms are present?
it cannot be picked up on blood culture so is diagnosed by endoscopy with biopsy
it causes pain/difficulty on eating/swallowing
What is candidaemia?
What is the response when it is detected?
candida being present in blood culture
the response involves:
- remove lines (where possible) from patient
- start antifungal therapy straight away
- check eyes and heart
Why are the eyes checked in candidaemia?
there is a 3-25% risk of occular candidosis following candidaemia
this is either candida chorioretinitis or endophthalmitis
Why is candida endophthalmitis difficult to treat?
it requires intravitreal antifungals (injecting into the eye)
Why should the heart be checked in candidaemia?
candida endocarditis is a rare consequence of candidaemia
What is candida endocarditis?
What groups of people are more commonly affected?
vegetations are seen on heart valves
it most commonly affects IV drug users and people who have had valve surgery
What symptoms are present in candida endocarditis?
- fever
- weight loss
- fatigue
- heart murmur
How is candida endocarditis treated?
it is difficult to treat without valve replacement
What causes renal candidosis?
What group of people are usually affected?
candida from the blood lodges in kidney tissue during filtration
it is most common in immunocompromised premature neonates
What are the typical symptoms of renal candidosis?
- fever
- abdominal pain
- oliguria (reduced urine output)
- anuria (failure to produce urine)
What causes a urinary tract candida infection?
In which groups of people is it most common?
it ascends from a genital tract infection/colonisation or from catheterisation
it is most common in:
- women
- diabetics
- damaged/abnormal urinary tracts
- ICU patients
Why is a urinary tract candida infection often hard to manage?
few antifungals will penetrate the urinary tract
What is candiduria?
isolation of Candida from urine
this may or may not be significant
22% of patients on ICU > 7 days develop candiduria
What is candida peritonitis?
What usually causes it and how is it diagnosed?
it is a complication of peritoneal dialysis
it is caused by perforation of the bowel during surgery (mixed bacterial/yeast infection)
it is diagnosed by culture of candida from peritoneal fluid
What are the symptoms of candida peritonitis?
How is it treated?
fever, abdominal pain, nausea and vomiting
it is treated by source control/drainage and antifungals
How is systemic candidosis diagnosed?
culture from a sterile site (e.g. blood, peritoneal fluid)
imaging results
What is the treatment for systemic candidosis?
it depends on candida sp. sensitivity, severity and need for oral agent
- echinocandins e.g. anidulafungin (IV)
- azoles e.g. fluconazole (oral)
- liposomal amphotericin B (IV)
What is hepatosplenic candidosis?
In which people is it most common?
it is a disseminated form of candidosis
it is seen in leukaemia and other haematological malignancies
What is the mechanism behind Hepatosplenic candidosis?
- during neutrophil recovery, yeasts lodge in liver and spleen (and rarely in kidney)
- this leads to abcess formation (bullseye sign), fever and liver function disturbance
How is the blood affected in hepatosplenic candidosis?
candidaemia (candida in blood) during period of neutropenia
this may or may not be detected
Why may antifungal therapy be ineffective in hepatosplenic candidosis?
dead fungus continues to trigger an inappropriate inflammatory response
this produces the symptoms
What is shown?
bullseye sign
abcess in the spleen seen in hepatosplenic candidosis
What are aspergillus and how are we exposed to them?
genus of moulds - filamentous fungi
they produce airborne spores
exposure to Aspergillus spores is universal by inhalation
airways may be colonised by Aspergillus sp.
What are the 4 main types of Aspergillus sp?
- aspergillus fumigatus
- aspergillus niger
- aspergillus flavus
- aspergillus terreus
What is shown here?
Aspergillus fumigatus
What is aspergillosis?
a reaction to inhaling Aspergillus
What is an aspergilloma?
a fungal ball
it is space occupying/non-invasive aspergillosis in the lung cavity
What are the 3 other types of reactions to inhaling Aspergillus?
allergic reaction:
- in asthma, cystic fibrosis
- allergic bronchopulmonary aspergillosis, allergic sinus disease
chronic infection:
- in chronic lung disease
- chronic pulmonary aspergillosis
invasive infection:
- occurs in immunocompromised patients (leukaemia)
- invasive pulmonary aspergillosis, invasive aspergillus sinusitis
In which types of patients is an aspergilloma common in?
patients with cavities from previous TB, sarcoid, surgery
involves formation of solid balls of fungus
What is the risk with aspergillomas?
aspergillomas are often indolent
but they may break up causing haemoptysis and are potentially fatal
What are the symptoms and signs of allergic forms of aspergillosis in asthma and CF?
allergic bronchopulmonary aspergillosis
- wheezing, breathlessness, loss of lung function, bronchiectasis
- airways inflammation
- IgE and IgG reaction to aspergillus
What are the treatments for allergic forms of aspergillosis?
responds to steroids and/or antifungal therapy
What is chronic pulmonary aspergillosis?
What are the symptoms and what does it look like on CT?
it is seen in COPD
- chronic respiratory symptoms such as cough, wheezing, breathlessness and chest pain
- consolidation and cavitation on CT
How is chronic pulmonary aspergillosis diagnosed?
a positive culture of Aspergillus from sputum and BAL
positive for aspergillus IgG
In which types of patients is invasive aspergillosis seen?
in haematological malignancies, stem cell and solid organ transplants
patients often have low neutrophil counts
What signs are seen on CT scans in invasive aspergillosis?
Halo sign and air cresent signs
What is the prognosis of invasive aspergillosis like?
moderate to poor prognosis even with aggressive antifungal therapy
How is aspergillosis diagnosed?
- culture
- serology
- imaging
What are the treatments for aspergillosis?
- resection of the lung in aspergilloma
- steroids +/- antifungals in allergic aspergillosis
- antifungals (itraconazole, voriconazole, amphotercin B) in CAP and invasive aspergillosis
