Fungi

Question 1

Histoplasma capsulatum

Answer 1

• a dimorphic fungi most often found in the Ohio and Mississippi river valleys of the midwest/central US
• spread via inhalation of spores and associated with bird and bat droppings and thus with caves and chicken coups
• in the immunocompotent, it tends to present with granulomas in the upper lobes/hilar regions which calcify and resemble TB as well as painful erythema nodosum
• in the immunodeficient, it causes disseminated infection and hepatosplenomegly
• diagnosis is made via serum or urine antigen tests
• KOH prep will reveal many, small, oval yeast in macrophages
• treat a localized infection with azoles and disseminated infection with amphotericin B

Question 2

Blastomyces dermatitidis

Answer 2

• a dimorphic fungi most often found in the Eastern US near the Ohio river valley and around the Great lakes
• spread via inhalation of spores
• immunocompotent individuals typically have a local lung infection with a patchy infiltrate or granuloma formation
• immunodeficient patients tend to present with symptoms of a cutaneous infection along with lytic bone lesions
• diagnosed via a urine antigen test
• KOH reveals broad based budding yeast approximately the size of red blood cells
• treat a localized infection with azoles and disseminated infection with amphotericin B

Question 3

Coccidioides immitis

Answer 3

• a dimorphic fungi most often found in the southwest US
• spread via inhalation of spores in dust and associated with earthquakes and dust storms
• presents as an acute pneumonia with fever, erythema nodosum, arthralgia, and nodules or cavitary lesions in the lungs
• disseminated infection in immunodeficient patients can spread to the skin, bone, and meninges
• KOH prep demonstrates thick-walled spherules, which are larger than RBCs and contain many endospores,
• treat a localized infection with azoles and disseminated infection with amphotericin B

Question 4

Paracoccidioides brasiliensis

Answer 4

• a dimorphic fungi most often found in South America
• spread via inhalation of mold spores
• presents with oral mucosal lesions, chains of cervical lymphadenopathy, and granuloma formation in the lungs
• form yeast that are much larger than RBCs and demonstrate captain’s wheel budding
• treat a milder infection with azoles and more severe with amphotericin B

Question 5

Malassezia furfur

Answer 5

• a cutaneous mycosis which thrives under hot and humid conditions as in sun exposed areas of the body
• causes pityriasis versicolor with hypo- and hyperpigmentation of the skin due to it’s degradation of lipids, which produces acid that damages melanocytes
• typically remains confined to the stratum corneum
• but babies receiving total parenteral nutrition are at risk for fungemia as the infusion contains lipids which promote fungal growth and entry into the body
• KOH prep reveals a “spaghetti and meatball” appearance
• should be treated with topical selenium sulfide, also known as selsun blue

Question 6

Dermatophytes

Answer 6

• includes the cutaneous mycoses known as microsporum, epidermophyton, and trichophyton
• which cause the pruritic rash known as tinea and can cause a nail infection known as onychomycosis
• KOH prep of skin lesions can diagnose the three and Wood’s lamp can also be used to identify microsporum
• preferred treatment for tinea is an azole but nail infections require terbinafine and refractory cases of either should be treated with griseofulvin

Question 7

Sporothrix schenkii

Answer 7

• a dimorphic fungi which causes a cutaneous mycosis referred to as rose gardner’s disease
• commonly found in soil and on plant matter and then introduced to humans via thorn pricks
• causes ulcers or subcutaneous nodules at the site of inoculation and the infection ascends via the lymphatics
• diagnosis is made via culture or biopsy, which will find granulomas filled with cigar-shaped yeast
• preferred treatment is azoles, but historically, saturated solutions of potassium iodide (SSKI) were used

Question 8

Candida albicans

Answer 8

• an opportunistic, dimorphic fungi that is catalase positive
• uniquely, it forms takes the mold form and grows germ tubes at higher temperatures while taking the yeast form with pseudohyphae at colder temperatures
• causes diaper rash in neonates, oral candida in those taking ICS who don’t properly rinse, and endocarditis in IV drug users
• women may experience vulvovaginitis characterized by pruritus, a thick white discharge, and pH below 4; especially if diabetic, taking antibiotics, or taking oral contraception
• esophagitis can be seen in the immunocompromised with CD4 count under 100 as an AIDS-defining illness and disseminated disease in others
• generally, treated with fluconazole or amphotericin B; however, nystatin is appropriate for oral or esophageal candida, and caspofungin can be used in refractory cases