Fungal Infection Flashcards
Explain the main differences between fungi (eukaryotes) and bacteria (prokaryotes), and the consequences for treatment of fungal infections
Fungal properties;
- Digest food extracellularly ( secret hydrolytic enzymes which can breakdown biopolymers to be absorbed for nutrition)
– saprophytes - Spread via spores over large distances – humans constantly exposed
- Eukaryotes
Differences to bacteria: (the list indicates what fungus have in contrast to bacteria
- Membrane-bound nucleus
- Cell wall
- DNA vs RNA
Main effect is that fungal infections are harder to treat
List the various types of fungal infection, the major fungal pathogens, and explain the mechanisms by which they cause disease
Fungal pathogens; primary; require a normal healthy host and opportunistic; compromised host
-
Allergies; E.g. Rhinitis, Dermatitis, Asthma
- Results in sensitization to the spores -> allergic reaction
- Inhalation of/contact with fungal spores may induce a wide range of allergic diseases:
- Rhinitis
- Dermatitis
- Asthma
- Allergic broncho-pulmonary aspergillosis (ABPA) caused by Aspergillus fumigatus
-
Mycotoxicoses
- A toxic reaction causes by the inhalation or ingestion of a mycotoxin (secondary metabolite of moulds)
- Typically eating poisonous mushrooms
- can cause;
Breathing problems, dizziness, severe vomiting, diarrhea, dehydration, hepatic and renal failure 6 days later, death, hallucination, recent studies have shown that it can help with depression
* Therapy: Gastric lavage and charcoal, liver transplant * Aflatoxin produced by Aspergillus flavus is amongst the most carcinogenic natural compound known which causes around 28% of Hepatic cell carcinomas worldwide
-
Mycoses:Candida
- Recent increase in infections
- It can be;
- No living tissue is invaded and there is no cellular response from the host
Black piedra –> (Piedraia hortae)
- No living tissue is invaded and there is no cellular response from the host
White piedra –> (Trichosporon beigelii)
Dandruff –> (Malassezia globosa)
Tinea nigra –> (Phaeoannellomyces werneckii
* Mucosal – Occurs in HIV/immunosuppressed patients particularly
* Cutaneous mycoses: Dermatophytes, or keratinophilic fungi. Produce extracellular enzymes (keratinases) which are capable of hydrolyzing keratin.
Tinea capitis (head/neck) •Superficial fungal infection of the skin of the scalp, eyebrows, and eyelashes, with a propensity for attacking hair shafts and follicles
Tinea pedis (feet = athletes foot)
Tinea corporis (body)
Tinea cruris (groin = jock itch)
Tinea unguium (finger/toenails)
* Subcutaneous mycoses: Chronic, localized infections of the skin and subcutaneous tissue following traumatic implantation of the aetilogic agent
* Systemic – Not seen in healthy individuals, associated with catheters, gut surgery, and chemotherapy Primary (Coccidioides immitis, Histoplasma capsulatum, Blastomyces dermatiditis, Paracoccidioides brasiliensis)
Opportunistic (Cryptococcus, neoformans, Candida, Aspergillus, Penicillium marneffei, The zygomycetes, Trichosporon beigelii, Fusarium)
Pathogenic Candida species:
- Candida albicans is an opportunistic commensal
- Mouth, throat, skin, scalp, vagina, fingers, nails, bronchi, lungs, or the gastrointestinal tract
- Usually due to impaired epithelial barrier functions
- Occur in all age groups
- Most common in the newborn and the elderly
- Respond readily to treatment.
- Occurs in HIV/immunosuppressed patients particularly
Most fungal infections are opportunistic and are acquired from the patient’s environment
Discuss diagnoses of fungal infections
Diagnosis of fungal infections
- Sample aquisition
- Skin
- Sputum
- Bronchoalveolar lavage
- Blood
- Vaginal swab/smear
- Spinal fluid
- Tissue biopsy
- Microscopy
- Culture
- Slow
- Prone to contamination
- Requires skilled sample collection
- Non-culture methods: Antibody- and antigen-based assays
Detect:
- Glucan
- Mannan
- Enolase
- Proteinase
- PCR (DNA)
Compare the major classes of antifungal drugs, and explain their mechanisms of action
3 targets:
- Cell membrane – target ergosterol production
- Fenpropimorph
- Azole antifungals
- Terbinafine
- Membrane function
- Polyenes
- Nucleic acid synthesis
- Pyrimidine analogs (5- Flucytosine)
- Used in combination therapy (not too effective alone)
- Cell wall
- Echinocandins – target cell wall production (β-glucan synthesis)
Nystatin and amphotericin B are both polyene antimicrobials aimed at INHIBITING ergosterol found in the fungal membrane
Define the terms superficial mycoses and deep mycoses, giving named examples of each type of infection
Mycosis – a fungal infection in animals
Superficial:
- Rash, in all age groups, responds readily to treatment -Outermost layers of skin/hair
- No living tissue is invaded and there is no cellular response from the host
- Black piedra –> (Piedraia hortae)
- White piedra –> (Trichosporon beigelii)
- Dandruff –> (Malassezia globosa)
- Tinea nigra –> (Phaeoannellomyces werneckii)
Cutaneous mycoses:
- Dermatophytes, or keratinophilic fungi.
- Produce extracellular enzymes (keratinases) which are capable of hydrolyzing keratin.
- Tinea capitis (head/neck): Superficial fungal infection of the skin of the scalp, eyebrows, and eyelashes, with a propensity for attacking hair shafts and follicles
- Tinea pedis (feet = athletes foot)
- Tinea corporis (body)
- Tinea cruris (groin = jock itch)
- Tinea unguium (finger/toenails)
Subcutaneous mycoses:
- Chronic, localized infections of the skin and subcutaneous tissue following traumatic implantation of the aetilogic agent
Systemic
- Not seen in healthy individuals
- Infect via resp, GI, IV devices, catheter, catheters, gut surgery, and chemotherapy
- Primary (Coccidioides immitis, Histoplasma capsulatum, Blastomyces dermatiditis, Paracoccidioides brasiliensis)
- Opportunistic (Cryptococcus, neoformans, Candida, Aspergillus, Penicillium marneffei, The zygomycetes, Trichosporon beigelii, Fusarium)
Mucosal
- Occurs in HIV/immunosuppressed patients particularly
