Fungal infections + antifungal chemotherapy Flashcards
What are dermatophytes and examples?
fungi that can cause superficial infection of skin, hair and nails such as Trichophyton, Microsporum and Epidermophyton`
How do Tinea and ringworm survive?
by spreading from host to host, can be zoophilic or anthrophilic
What is Tinea Pedis and its risk factors and symptoms?
Athletes foot, fungal infection between the toes, risk factors include damp feet, tight shoes with poor ventilation and being barefoot in communal areas. Symptoms include itching, flaking, maceration, splitting and fissure, burning, inflammation and pain
What is candida and what is the most prevalent form?
A type of yeast, most common cause of superficial skin infection and candida Albicans which causes thrush is the most prevalent. Thrush is characterised by creamy white plaques/ discharge, itchiness and swelling may also present
What is systemic candidiasis?
when candida affects multiple organs, can cause eye infections, CNS infection (meningitis), pneumonia, UTIs and endocarditis
Describe candida transmission
can be exogenous or endogenous
What treatment was first available for fungal infections?
active azoles and amphotericin B
What are the treatment options for tinea?
OTC creams, sprays or powders, azoles which suppress growth and allylamines such as terbinafine which are fungicidal. Other options are: Zinc undecylenate/undecylenic acid or Tolnaftate 1%
What are the treatment options for nail infections?
2 OTC topical agents specifically for infected nails are: Urea 40% (canespro) amd Amorolfine 5% (Curanail)
When should you refer a patient with a nail infection to GP?
when they come with more than 2 infected nails
What are the treatment options for oral candida?
Oral Miconazole gel (Daktarin) for a week
What are the treatment options for vaginal thrush?
intravaginal Clotrimazole cream or pessary & women aged 16-60 can be given single dose 150mg Fluconazole capsule
What patient counselling should a pharmacist give on self-care to prevent fungal infections?
washing and drying clothes thoroughly, avoid sharing towels, wash clothes and towels frequently, wear loose fitting clothes, cotton socks, keep feet cool, avoid scratching
What is a pharmacists’ role in anti-fungal stewardship?
prescription review, de-escalating when appropriate, optimising drug therapy, monitoring and restoring immune response
What types of antifungal treatments are there?
7, Polyene antifungals, Imidazole antifungals, Triazole antifungal, Allylamines –terbinafine, Echinocandin antifungals, Antimetabolite antifungals & Griseofulvin
Give 3 serious fungal diseases
Blastomycosis: affects lungs of healthy patient, Pneumocystis pneumonia: important in AIDS patients, treat with co-trimoxazole and anti-leishmaniasis & Cryptococcosis or Crytococcal meningitis: big cause of death in AIDS patients
How do fungal diseases occur?
colonisation occurs when spores of fungus are inhaled, aspergillius spores ubiquitous in air and affects the lungs
Describe the structure of fungi
unicellular eurkaryotes, no cell walls, cell membranes contain ergosterol instead of cholesterol, GPI, glucan, chitin
What are polyene antifungals, some examples and their MoA?
antifungals with hydrophobic part inside membrane and hydrophilic outside membrane, eg Amphotericin B which is a natural product from Streptomyces nodosus (soil bacterium) which binds to ergosterol in fungal cell membrane and amphotericin- ergosterol complex form pores in membrane causing leakage, Structure of polyene antifungals: multiple chiral centres made of units of acetate with alternating oxygen pattern
What is Amphotericin B used to treat?
Oral infections by local application, used IV to treat systemic fungal infections. Toxic to kidneys
What is Nystatin and how does it work?
Closely related polyene, from strains of Streptomyces Noursei, binds to ergosterol used to treat candida Albicans infections of skin, available as creams and ointments
Cholesterol and ergosterol are both derived from what?
squalene, differ by a couple of extra bonds and a methyl group
What is Terbinafine and how does it work?
hydrophobic drug which inhibits squalene epoxidase, a rate-limiting in ergosterol synthesis, used topically or orally for skin infections
What is the purpose of cytochrome p450 14 α demethylase?
enzyme that catalyses a reaction most susceptible to attack in the conversion of squalene to ergosterol
What are some examples of azole antifungals and how do they work?
3 IMIDAZOLES: ketoconazole, Miconazole, ticonazole, 4 TRIAZOLES: fluconazole, itraconazole, voriconazolem posaconazole, they all inhibit CYP450 14 α- demethylase
Why can’t azoles and polyenes be given together?
polyenes rely on sterol binding in order to function
How do echinocandin antifungals work?
Target 1,3 – β glucan synthesis. Β glucans are carbohydrate polymers that provide cross-links to other cell wall components, similar to peptidoglycan. Example: Caspofungin, Anidulafungin and micafungin
How do antimetabolite antifungals work giving some examples?
5-Fluorocytosine acts as an inhibitor of both DNA and RNA synthesis via the intracytoplasmic conversion of 5-fluorocytosine to 5-fluorouracil. Mainly used in combo with Amphotericin B
What is the MoA of Griseofulvin?
interferes with microtubule assembly, produced from strains of penicillium fungi, orally used to treat skin infections, doesn’t inhibit candida
