Fungal Infections of the Skin

Question 1

Dermatophytosis organisms

Answer 1

causes by dermatophytes. infect superficial keratinized structures (skin, hair, nails). three major genera, epidermophyton, trichophyton, microsporum. all transmit by direct contact except microsporum, which is by zoonosis from pets. all produce keratinases that allow invasion of the cornified cell layer

Question 2

dermatophytosis pathogenesis

Answer 2

form chronic infections in warm, humid areas on body surface. named for affected body part. form inflamed circular border of papules/vesicles. transmitted by fomites or by autoinoculation from other body sites

Question 3

dermatophytosis diagnosis

Answer 3

exam: itching, redness, tight/wet clothing. Scraping from skin/nail, treat with KOH, examine remains for spores/hyphae. culture on sabourauds agar, PPD with trichophytin, microsporum show fluorsecence under wood’s lamp

Question 4

dermatophytosis treatment

Answer 4

topical antifungal cream: terbinafine, undecylenic acid, miconazole, tolnaftate. can use oral griseofulvin

Question 5

tinea versicolor organisms and pathogenesis

Answer 5

overgrowth of normal flora Malassezia furfur or globosa. superficial skin infection only cosmetic. hypo/hyper pigmented areas with scaling/itching. family often has a history of infection

Question 6

tinea versicolor diagnosis

Answer 6

skin scrapings, treat with KOH and stain with blue. look for mix of budding yeasts and short cigar butt hyphae. examination with wood’s lamp might show coppery-orange fluorescence

Question 7

tinea versicolor treatment

Answer 7

topical selenium sulfide or azole for 2 weeks. can use oral azoles too

Question 8

tinea nigra organisms and pathogenesis

Answer 8

organism is the werneckiis. spores in soil enter injury, germinate in the keratinized skin layers. generate a brown pigment. seen in southern coastal US.

Question 9

tinea nigra diagnosis

Answer 9

brown spots, slight itch. treat skin scrapings with KOH, examine for thick septate, branching hyphae with dark pigment in their walls. culture on sabouraud’s agar. shiny black colonies in 1 week

Question 10

tinea nigra treatment

Answer 10

topical keratolytic agen to break down infected skin and a topical azole

Question 11

sporotrichosis organism

Answer 11

sporothrix schenckii. thermally dimorphic!! found on vegetation, often seen in gardeners of roses

Question 12

sporotrichosis pathogenesis

Answer 12

thorn puncture. yeasts grow at site and form painless pustule or ulcer. suppurating subcutaneous nodules. symptoms wax and wane over the years. may progress to disseminated disease and meningitis if immunosuppressed. patients with COPD and long term corticosteroid use may develop pulmonary probs from inhaling spores

Question 13

sporotrichosis diagnosis

Answer 13

painless pustule or ulcer. history of gardening, farming, etc. history of ineffective antibiotic treatment. AIDS patients may have nodules on whole body. tissue biopsy shows round or cigar shaped budding yeasts. culture shows hyphae with oval conidia in clusters at tip of slender conidiophores (daisy shaped)

Question 14

sporotrichosis treatment and prevention

Answer 14

treat with itraconazole or other azoles. for more serious types, amphotericin B. wear gardening gloves to prevent

Question 15

chromomycosis organism

Answer 15

chromoblastomycosis or dermititis verrucosa. caused by dermatiaceous fungi: fonsecaea, phialophora, cladosporium. found in soil in the tropics, conidia or hyphae are gray or black

Question 16

chromomycosis pathogenesis

Answer 16

introduced into legs or feet with injury by wood splinters or thorns. gradually progressive subcutaneous disease. granulomas form as immune system attempts to contain. wartlike lesions spread from initial site over the years

Question 17

chromomycosis diagnosis

Answer 17

history of farming or travel. wartlike dark lesions. crusting abscesses along lymphatics. black dots among lesions. KOH mount from skin scrapings show dark colored septate hyphae or conidia. biopsy shows round fungal cells inside leukocytes or giant cells. ELISA for some species

Question 18

chromomycosis treatment and prevention

Answer 18

oral flucytosine and itraconazole. combine with local surgery. cryosurgery can be effective. topical application of heat from pocket warmers also helps reduce and reverse fungal growth over the months. wear shoes!!!

Question 19

mycetoma organism

Answer 19

petriellidium or madurella. found in soil, enters in wounds. rare in the USA

Question 20

mycetoma pathogenesis

Answer 20

replicating fungi form abscesses. pus containing compact colored granules forms and drains through the local sinuses. looks very similar to actinomycosis, forms in foor, lower leg, or hand rather than the face though. granulomatous inflammatory response in the deep dermis and subcutaneous tissue may extend to bone. after years of infection, initial painless nodule swells and bursts!!!!

Question 21

mycetoma diagnosis

Answer 21

needle biopsy and culture. grains in the pus. Xray to see if bone is involved. differentiate from actinomycosis by staining. tissue gram stain to see fine gram positive branching filaments of actinomycetoma grain. silver or acid schiff stain to see larger hyphae of eumycetoma.

Question 22

mycetoma treatment

Answer 22

first attempt antifungal therapy: admit for initial IV amphotericin B, add antibiotics for secondary infections and send home with oral azole. surgical excision of abscesses necessary usually

Question 23

candidiasis organisms

Answer 23

candida albicans. large, yeastlike, oval with a single bud. may also appear as pseudohyphae or hyphae when invading tissues

Question 24

candidiasis pathogenesis

Answer 24

adhesins for attachment, acid proteases and phospholipases for tissue invasion, phenotypic switching changes antigen expression and tissue affinity. syndromes range from trivial superficial to life threatening systemic. may involve any anatomical structure. difficult to diagnose as a pathogen since they re normal flora

Question 25

common occurences of candidiasis

Answer 25

diaper rash, vaginitis, thrush/esophagitis.

Question 26

less common occurences of candidiasis

Answer 26

less common are skin with overgrowth, and folliculitis forming a boil, chronic mucocutaneous candidiasis, infection of entire GI tract, systemic and disseminated infections

Question 27

candidiasis diagnosis (exam)

Answer 27

red, wet itchy skin. endoscopy finds GI things. ultrasound and CY find liver/spleen and abdomen things. endocarditis seen through echocardiogram. tissue biopsy is often helpful, use bronchoalveolar lavage for lungs.

Question 28

candidiasis diagnosis (lab)

Answer 28

exudates and biopsies show mix of budding yeasts, pseudohyphae, and hyphae. gram positive. KOH smear, white, blue and H&E stains. culture shows large colonies on agar. germ tubes form in serum. positive culture results from sterile sites are diagnostic. culture from nonsterile sites may still give evidence of increased colonization. bloodwork cultures in disseminated infections. urinalysis for kidney infections. serum alkaline phosphatase for liver/spleen. serum assays for cell wall components are available.

Question 29

signs of disseminated candidiasis

Answer 29

persistent leukocytosis, neutropenia, other risk factors, fever remining despite antibiotic coverage.

Question 30

candidiasis treatment

Answer 30

azoles. azole resistant: echinocandins. drain abscesses, prostetic join infection requires joint removal. endocarditis requires valve placement. supplement drug treatment by reducing predisposing factors