Exam2 fungal infections Flashcards
Adverse effects of nystatin
80% of patients are nephrotoxic if given orally
Distribution of azoles
Orally available; cola/acid helps absorption of itraconazole
Distribution of griseofulvin
Lipids increase oral absorption, concentrates in dead keratinized layer of the skin
How to treat diaper rash (Candida albicans)
Keep skin dry, azole creams, clotrimazole
In ergosterol production, where do allylamines (terbinafine, tolnaftate) and azoles act, respectively?
Squalene epoxidase (squalene –> 2,3-oxidosqualene); C14-a-demethylase (Lanosterol–> ergosterol and cholesterol)
Mechanism of Nystatin?
Fungicidal; Binds ergosterol and opens a pore to make membrane leaky
Mechanisms of benzalamine (butenafine) and allyamine (tervinafine, tolnaftate)
Fungicidal; Inhibits squalene epoxidase leading to a toxic accumulation of squalene
Mechanisms of griseofulvin
Fungistatic; Binds microtubules to inhibit spindles leading to multinucleate effects
Name cutaneous fungal infections
Malassezia, Dermatophytes (microsporum, epidermophyton, trichophyton)
Name different skin mycoses
Cutaneous fungal infections, subcutatneous infections, opportunistic mycoses
Name mechanism of azoles (Fluconazole, Itraconazole, Clotrimazole, Miconazole, Ketoconazole
Fungistatic; Binds fungal p450 (Erg11, C14-a-demethylase) blocking production of ergosterol
Name opportunistic mycoses
Candida albicans part of normal flora
Name subcutaneous fungal infections and how they infect
Enter through skin followed by subcutaneous or lymphatic spread; Sporothrix
Pathogenesis of dermatophytes
Monomorphic molds secrete proteases and keratinases, fungal antigens cause inflammation, grow best in cooler temps (not 37C)
Resistance of nystatin
acquired is rare, fungi can reduce ergosterol on membrane
Resistance to azoles
Altered cytochrome p450, increased efflux
Resistance to butenafine, terbinafine, tolnaftate
rare
Spectrum of azoles
Most widely used antifungal and spectrum varies by agent
Spectrum of butenafine, terbinafine, tolnaftate
Broad, dermatophytes, Candida, Sporothrix
Spectrum of griseofulvin
Dermatophytes
Spectrum of nystatin
Active against yeast and molds, dermatophytes are intrinsically resistant
Three major genuses of dermatophytes: ring worm, tinea jock itch, athlete’s foot
Trichophyton, Microsporum, Epidermophyton
Three modes of dermatophyte transmission
Anthropophillic (persion to person fomite), Zoophilic (animal to human), Geophilic (soil)
Toxicity of azoles
Drug-drug interactions, hepatotoxicity, neurotoxicity, alters hormone synthesis (avoid during pregnancy)
toxicity of griseofulvin
TERATOGENIC, DISULFIRAM-LIKE REACTION, monitor hematology, renal and hepatic fxn
Toxicity to butenafine, terbinafine, tolnaftate
Topical, severe hepatitits if given orally, and drug-drug interactions; avoid giving to pts with liver disease
Treatment of dermatophytes
Topical griseofulvin, terbinafine, itraconazole for 1 month; Oral for hair and nail infections (monitor for hepatotoxicity)
Treatment of cradle cap?
Selenium sulfide shampoo
What can also lead to infection with Candida
Immune difficiencies and prior antibiotic use (opportunistic infection)
What causes cradle cap?
Inflammatory reaction to Malassezia
What causes diaper rash?
Candida albicans, usually a secondary infection with an antibiotic treatment
What causes rose gardener’s disease? Pathogensis? Treatment?
A puncture wound with Sporothrix schenckii; spread along lymphatic channels forming nodular lesions, need to biopsy a lymph node to diagnose; Oral itraconazole for 3-6 months, heat for pregnant women
What causes tinea pedis (ringworm), and tinea capitis?
Trichophyton rubrum (transfers at swimming pools); Trichopyton tonsurans (child to child)
What causes tinea versicolor?
Malassezia furfur: yest converts to mold and requires lipids for growth, grows in areas rich with sebaceous glands. Looks hypopigmented or hyperpigmented.
What is a less common cause of tinea pedis and cruris?
Epidermophyton floccosum
What is the main way to diagnose a fungal infection? Others?
10% KOH test and collect the skin on to a slide to look under a microscope; Wood’s lamp, can culture on Sabouraud media, skin biopsy w/ periodic acid-schiff stain
What is the resistance to griseofulvin
change in beta-tubulin
What to dermatophytes require for growth?
Keratin
Where does Microsporum grow? Diagnosis?
Hair (ectothrix) and skin; Wood’s light blue-green
Why is compliance a problem with griseofulvin?
Patient has a hard time taking drug for 4-6 weeks.
T/F: Candida albicans is an opportunistic infections
True
How do you diagnose a Candida albicans infection?
typically based on clinical appearance
Name three genera of dermatophytes
Trichophyton, Microsporum, Epidermophyton
most common cause of tinea capitis in US
Trichophyton tonsurans
most common cause of tinea pedis
Trichophyton rubrum
What microsporum is zoophilic that transfers through cats and dogs?
Microsporum canis
What microsporum is geophilic?
Microsporum fulvum
How should you treat a pregnant pt who has Sporothrix schenckii?
Apply heat to affected are (itraconazole is harmful during pregnancy)
What is this disease? What typically causes it? What does its KOH test look like? What’s the treatment?
Tinea versicolor; Malassezi furfur; Spaghetti and meatballs; Salenium sulfide shampoo
What organism is identified by the KOH test below (macro and microconidia)
Trichophyton rubrum
What organism if identifiable by its KOH test below (spindle shaped macroconidia)
Microsporum
What organism is identifiable by it’s KOH test below? (Dumbell shaped macrosporidum)
Epidermophyton floccosum
What organism is identifiable by its KOH test below? (rosette formation)
Sporothrix schenckii
