Theme 1: Lecture 4: Fungal pathogens Flashcards
What is the normal/reference range?
defines the values of a biochemical test found in healthy subjects against which patient values can be compared
What factors affect reference ranges?
- age
- gender
- diet
- pregnancy
- time of month
- time of day
- time of year
- weight
- stimulus
What is HbA1c?
- stable glycosylated haemoglobin
- % concentration indicates cumulative glucose exposure
What are the two types of yeast growth forms?
- hypha = moulds
2. yeast cells = yeasts
How do yeasts reproduce?
asexually and/or sexually, spore formation
What are saprophytes?
growing on dead/ decaying organic matter
What are the 3 types of fungi that cause superficial infection?
- dermatophytes
- malassezia
- candida
What do superficial infections affect?
skin, hair, nails and mucocutaneous tissue
What are the 2 types of fungi that cause systemic infection?
-candida
-aspergillus
Affects deep-seated organs
What are dermatophytes and where do they originate?
- groups of moulds
- causes of disease in skin, hair and nail
- originate in soil, other animals/humans
What does geophillic mean?
originate from soil
What does zoophilic mean
transmission from animal to human
what does anthropophillic mean?
human to human transmission
What is the medical name for athletes foot?
tinea pedis
What is the medical name for fungal nail disease?
tinea unquium / onychomyosis
What is the medical name for ‘jock itch’?
tinea cruris
What is the medical name for ringworm?
tinea corporis
What is the medical name for scalp ringworm?
tinea capitis
What are the symptoms of tinea pedis?
- itching, flaking, fissuring of skin
- soles of feet dry and scaly
- “moccasin foot” - if skin of whole of foot affected
- may spread to infect toe nails
Which fungi is typically the cause of tinea pedis?
trichophyton rubrum
What are the typical fungal causes of tinea unguium?
trichophyton rubrum and T. interdigitale
What are the 4 main types of fungal nail infection?
- Lateral/ distal subungual
- superficial white
- proximal
- total nail dystrophy
What happens to your nails with tinea unguium?
thickening, discolouring, dystrophy
What are the symptoms of tinea cruris?
- itching, scaling, erythematous plaques with distinct edges
- satellite lesions can be present
- may extend to buttocks, back and lower abdomen
What is the typical cause of Ttinea cruris?
T. rubrum
In what age group is tinea capitis usually seen?
mainly pre-pubescent children
What are the signs of tinea capitis?
slight inflammation, scaly patches, with alopecia, “black dots”, “grey patches”, severe inflammation
What is kerion celsi?
areas of severe inflammation - boggy, inflamed lesions, usually from zoophilic dermatophytes
What are the signs of tinea corporis?
- circular, single or multiple erythematous plaques
- may extend from e.g scalp/groin
- invasion of follicle - “majoccis granuloma”
How do we treat dermatophyte infections?
- topical antifungal (not curative/ reduces spread only)
- terbinafine, clotrimazole, miconazole
What is malassezia?
- genus of years
- part of normal skin flora in all humans from after birth
- highest levels on head and trunk
What diseases does malassezia cause?
- pityriasis versicolor
- role in seborrheic dermatitis
- atopic eczema
What are the features of pityriasis versicolour?
- hyper or hypo pigmented lesions
- upper trunk
- between puberty and middle age
- more common in tropics
- relapsing
How does pityriasis versicolor appear under a microscope?
“spaghetti and meatballs” - yeast cells and hyphal segments
What is the treatment for pityriasis versicolor?
topical antifungals e.g clotrimazole, if fails oral fluconazole or itraconazole
What is the candida genus?
- large genus of yeasts
- often colonises the mucosal surface and GI tract in healthy people
- causes of superficial mucosal (oral and vaginal) disease “thrush”, skin disease and keratitis
Name some candida species
- candida albicans
- candida glabrata
- candida parapsilosis
- candida krusei
What are the 4 superficial candida infections arising in oral mucosa?
- acute pseudo-membranous
- white dots
- low CD4 count - common in patients with AIDs
- younger patients and people who use steroid inhalers - chronic atrophic
- older patients
- erythema (less white dots/ more red) - angular cheillitis - inflammation of one or both corners of mouth
- chronic hypoplastic (oral leukoplakia)
- lesions may undergo malignant transformation
What are the causes of oral candidosis?
- HIV/AIDs - T-cell immunity important to prevent mucosal candidosis
- antibiotic use - supresses normal flora, less competition for years
- head and neck cancer - radiotherapy/chemotherapy affect salivary secretions
- general debilitation in hospitalised patients
What are the symptoms of candida vulvovaginitis?
- pruritis (itch), burning sensation, +/- discharge
- inflammation of vaginal epithelium, may extend to labia majoria
- often florid infections during pregnancy
- 10% will suffer from recurrent vulvovaginal candidosis
What is the treatment for candida vulvovaginitis?
-usually oral azoles, fluconazole highly effective
When can oral azoles to be used?
in pregnancies
increases the risk of teratologies in child e.g heart defects, use topical azoles
Which species of candida is the most common in causing infection?
Candida albicans
Give examples of names of systemic candidosis infections
- CNS candidosis
- pulmonary candidosis
- candida endocarditis
- candida peritonitis
- renal candidosis
- urinary tract candidosis
In what condition do we mainly see candida oesophagitis?
HIV
What are the symptoms of candida oesphagitis?
pain/ difficulty on eating/ swallowing
What is candidaemia and how do we respond?
- candida in blood culture
- response: remove lines/catheters, start antifungal therapy, check eyes for endophthalmitis and heart for endocarditis
What 3 types of candida infections can you acquire in the eye?
- ocular candidosis
- chorioretinis
- candida endopthalmitis
What is candida endocarditis?
- vegetations on heart valve
- fever, weight loss, fatigue, murmur
- rare consequence of candidaemia
- difficult to treat without valve replacement
Why is managing urinary tract candida infections difficult?
few antifungals are secreted in urine
What is candida peritonitis?
- complication of peritoneal dialysis
- perforation of bowel during surgery (mixed bacterial/ yeast infection)
- fever, abdominal pain, nausea, vomiting
What is aspergilus?
- genus of moulds - filamentous fungi
- producing airborne spores
- exposure to aspergillus spores universal by inhalation
- airway may be colonised by aspergillus sp
What are the 4 most important medical species of aspergillus in order?
- aspergillus fumigatus - most common
- aspergillus niger
- aspergillus flavus
- aspergillus terreus
What does aspergillus fumigatus look like under a microscope?
blue/ green colonies with white margins
What is aspergillosis?
- reaction to inhaled aspergillus
- space occupying/ non invasive - lung capacity
- Usually, aspergillosis is caused by inhaling Aspergillus spores. Most people inhale these spores every day without being affected. But if the immune system is weak, infection is more likely because aspergillosis is an opportunistic fungal infection
- usually affect respiratory system
What is an aspergilloma?
solid balls of fungus
How can aspergillosis cause an allergic reaction?
in asthma and CF patients:
- allergic bronchopulmonary aspergillosis, allergic sinus disease
- chronic infection - chronic pulmonary aspergillosis
- invasive infection in immunocompromised - invasive pulmonary aspergillosis, invasive aspergillus sinusitis
How do aspergillomas arise and how can they become dangerous?
- arise in patients with cavities from previous tuberculosis, sarcoid, surgery
- break up causing haemoptysis and are fatal
What are the features of allergic forms of aspergillosis in patients with asthma and CF?
- a.k.a allergic bronchopulmonary aspergillosis
- wheezing, breathlessness, loss of lung function, bronchiectasis
- airway inflammation
- raised total IgE
- IgE and IgG reactions
- responds to steroids sometimes antifungal therapy added
What is chronic pulmonary aspergillosis (CPA)?
-chronic obstructive pulmonary disease
What is invasive aspergillosis?
- only occurs in patients with haematological malignancy, stem cell and solid organ transplant
- low neutrophil counts
- angioinvasion of lung tissue
- halo and air crescent signs of chest CT
- moderate to poor prognosis, even with aggressive antifungal therapy
How do we treat aspergilloma?
resection of aspergilloma
How do we treat allergic aspergillosis?
steroids +/- antifungals
Summary of aspergillus
- causing pulmonary or sinus disease
- inhalation of aspergillus spores
Which is the best antifungal for urinary tract candidosis?
fluconazole
Where is T.rubrum most commonly found?
on feet
Which 3 main infections does T.rubrum cause?
- tinea pedis
- tinea crusis
- tinea corporis
