22 - Fungal Diseases 2 Flashcards
How are superficial, cutaneous and subcutaneous mycoses are transmitted
Direct contact
Superficial mycoses
- Infections limited to the outer surface of hair and skin
- Mostly occur in the tropics
Piedras
Infections of hair shaft
Tineas
Infections of outer layers of skin, hair and nails
Examples of superficial mycoses
- Trichophyton spp.
- Malassezia furfur
Trichophyton spp.
- Cause tinea capitis (infection of scalp hair)
- Example of a dermatophyte
Malassezia furfur
- Causes tinea versicolor
- Brownish-red scales on skin of trunk, neck, face, arms
Cutaneous mycoses
- Infections of skin cells
- The most common fungal diseases in humans
- Caused by Dermatophytes
- Common genera are Microsporum, Trichophyton
Other names for cutaneous mycoses
Dermatomycoses,
ringworms, or tineas
Dermatophytes
- A common name for
filamentous fungi that
cause skin infections - Require keratin as C
source for growth
Examples of cutaneous mycoses
- Tinea corporis: ringworm of the body
- Tinea pedis: athlete’s foot
- Tinea unguinum: nail infection.
Subcutaneous mycoses
- Caused by Dermatophytes that infect under the skin
- Fungi normally saprophytic inhabitants
of soil and decaying vegetation - Introduced via puncture wound
- Disease develops slowly, often over years
Example of subcutaneous mycoses
Sporotrichosis
Sporotrichosis
- Caused by Sporothrix schenckii
- Found on plants (roses, hay)
- Dimorphic fungus (filamentous form in environment, yeast form
in hosts or lab) - Transmitted via infected cats
When can opportunistic fungi become pathogenic
- Introduced to new environment,
- Outcompetes other resident microbes
- Host becomes immunocompromised (e.g. prolonged antibiotic use, cancer, AIDS)
Aspergillosis
- Most widely distributed fungal pathogen (soil, dust, food, water)
- Inhalation of conidiospores can lead to asthma and bronchitis
- Fungal colonies form within lungs (form tangled mass of hyphae)
- May then spread to form disseminated aspergillosis
Aspergillus fumigatus
Most common cause of pulmonary aspergillosis
Aspergillus flavus
Most common cause of superficial infection
and invasive disease of immunosuppressed patients
Candidiasis
- Caused by dimorphic fungi of genus Candida
- Invade through body fluids as yeast cells, invade through tissues as filaments
- Main pathogen is Candida albicans
- Member of normal microbiota (GIT, RT, vag, mouth)
- Most diverse range of diseases of fungal pathogens
Oropharyngeal candidiasis
- Thrush
- Newborns, weakened immune system
- Small white flecks on mouth, tongue
Intertriginous candidiasis
Groin, skin folds, nappy rash
Candidal vaginitis
- If normal flora Lactobacillus decreases due to antibiotic
therapy, oral contraceptives, pregnancy etc. - Candida may proliferate, causing yellow discharge from vagina
Candidaemia
Disseminated disease, mortality can be 50% if invasion of blood stream or visceral organs in immunocompromised
Pneumocystis pneumonia (PCP)
- Serious infection caused by Pneumocystis jiroveci
- Opportunistic pathogen in immunocompromised hosts
- Transmission by inhalation of respiratory droplets, or via sputum
PCP symptoms
- Difficulty breathing
- Fever, cough, chest pain
- Lesions in lymph nodes
Diagnosis of PCP
- Cannot be cultured
- Chest X ray
- Sample from lungs
- PCR
Treatment of PCP
- Does not respond to anti-fungal drugs
- Treatment with trimethoprim-sulfamethoxazole
Mycotoxins
Natural contaminants of many foods and agricultural products (e.g. aflatoxins)
Aflatoxin
- Aspergillus spp.
- Cereals, nuts
- Liver necrosis, cancer
