18 - Endemic Mycoses

Question 1

What are characteristics of endemic mycoses? How are they spread?

Answer 1

They are all dimorphic - they exist as mold in the cold (25-30) and yeast or spherule at 37 degrees.

Infection is by inhalation of infectious particles into the lungs or cutaneously.

Cutaneous lesions can be observed as a result of dissemination which can be life-threatening in days.

Question 2

Endemic mycoses caused by all three organisms can cause infection in _________ individuals.

Answer 2

Immunocompetent individuals, but immunocompromised people have a higher incidence of infection and the infection is more severe.

Question 3

What disease is caused by histoplasma capsulatum? What is the infectious form?

Answer 3

Histoplasmosis.

Thermally dimorphic; in nature it exists as a mold exhibiting macro (tuberculate) conidia and microconidia.

MICROconidia is the infectious form.

Question 4

What is the morphology of histoplasma capsulatum?

Answer 4

Yeast morphology.

Intracellular mononuclear phagocytes with a NARROW bud neck.

Question 5

What’s the epidemiology of histoplasma capsulatum?

Answer 5

Localized to broad resions of the mississippi and ohio river valleys.

Found in soil rich in nitrogen often from bird and bat droppings.

Most residents of endemic areas are exposed by 20 years of age.

Question 6

What are the clinical symptoms of Histoplasma capsulatum? What is the time frame by which symptoms will occur?

Answer 6

Low inoculum-asymptomatic infection occurs in 90% of individuals.

Heavy inoculum-flulike illness with fever, chills, headache, couch, myalgias, and chest pain.

Symptoms will occur within 3-17 days. Most acute cases resolve with treatment for symptoms without antifungal treatment.

Question 7

Who is particularly susceptible to Histoplasma capsulatum? What occurs?

Answer 7

Immunocompromised and children - they can get acute disseminated histoplasmosis which can present with septic shock-like symptoms including fever, hypotension, pulmonary infiltrates and acute respiratory distress.

If untreated, histoplasmosis is fatal within days to weeks (regardless of immune status).

Question 8

How would you detect Histoplasma capsulatum in the lab?

Answer 8

direct microscopy - yeast cells are usually intracellular and clustered together.

Culture of blood, bone marrow, or other clinical material.

Serology-inducing antibody and antigen detection.

Question 9

What is the treatment for Histoplasma capsulatum?

Answer 9

Based on patient history whether or not antifungal treatment is necessary.

• once symptoms subside pt may not be free of histoplasma
• immune system will keep it below symptomatic levels, but can be reactivated if the immune system becomes weakened.

Treat will itraconazole and/or amphotericin B.

Question 10

What infection is caused by blastomyces dermatitidis? What is the morphology of this?

Answer 10

Blastomycosis.

Thermally dimorphic. Microconidia at 25 degrees. In tissue or culture at 37 degrees nonencapsulated yeast-like cells with a BROAD bud neck are seen.

Question 11

What is the epidemiology of blastomyces dermatitidis?

Answer 11

Endemic areas overlap with those of histoplasmosis and include the southeastern and south central states, especially those bordering the mississippi and ohio rivers, midwest states, and areas bordering the great lakes.

Found in decaying organic matter (soil and decaying leaves).

Question 12

What bug was responsible for a Wisconsin hyperendemic that occurred in 2015?

Answer 12

Blastomyces dermatitidis

Resulted from people tubing in the Little Wolf River in Waupaca County.

Question 13

What clinical symptoms are associated with blastomyces dermatitidis?

Answer 13

Severity depends on dose of the inoculum and immune status of pt.

Symptomatic disease occurs in less than 50% of infected individuals. May present at pulmonary disease.

Mild: flu-like symtoms
Severe: resemble bacterial pneumonia and chronic may resemble TB or lung cancer.

Question 14

What is the incubation time of blastomyces dermatitidis?

Answer 14

4-6 weeks following exposure.

Question 15

Besides pulmonary disease, how else may blastomyces dermatitidis present as?

Answer 15

Extrapulmonary desiseminated disease; chronic cutaneous involvement most common.

Lesions may be pustular, ulcerative-nodular, and verrucous with crusted surfaces and raised serpiginous borders.

Usually painless and localized to exposed areas such as the face, scalp, neck, and hands.

Question 16

What occurs if blastomyces dermatitidis is untreated? Who is it uncommon in?

Answer 16

It will become chronic with remissions and exacerbations

Disseminated disease can occur in bone, prostate, liver, spleen, kidney, and CNS.

Relatively uncommon in AIDS and other immunocompromised pts.

Question 17

How would you diagnose blastomyces dermatitidis?

Answer 17

Microscopic visualization of the fungus in tissue of sputum, bronchoalveolar lavage, or lung biopsy. Broad based budding yeast are indicative of blastomyces.

Confirmation by culture grown at both 25-30 degrees and 37 degrees. Mold can take 4 weeks to grow.

Cultures should be handled carefully in a hood to prevent exposure to lab personnel.

Question 18

What is the treatment for blastomyces dermatitidis?

Answer 18

Severity of infection, clinical form, immune status or pts, and toxicity of antifungal agent need to be taken into consideration when deciding how to treat.

Usually use amphotericin B or itraconazole.

Question 19

What infection is caused by coccidioides immitis and coccidioides posadasii?

Answer 19

Coccidioidomycosis, also called desert rheumatism, cali fever, desert fever, san joaquin fever, and valley fever.

These two organisms are indistinguishable.

Question 20

What is the morphology of coccidioides immitis and coccidioides posadasii? What is the infectious form?

Answer 20

Thermally dimorphic.

Mold in the cold: mold form produces arthroconidia which is the infectious form.

In the heat (37 degrees C) endosporulating spherules are observed.

Question 21

What’s the epidemiology of coccidioides immitis and coccidioides posadasii?

Answer 21

Reportable disease endemic to the desert southwest.

Found in the soil and growth is enhanced by bad and rodent droppings. Exposure to arthroconidia is greatest during late summer b/c of dusty conditions.

Question 22

What are the clinical symptoms of coccidioides immitis and coccidioides posadasii?

Answer 22

Most virulent mycotic pathogen; inhalation of few arthroconidia leads to disease.

~60% asymptomatic pul-disease or self-limited fluilike illness for 7-21 days following exposure.

10% have allergic rxn with macular rash, erythema multiforme, and erythema nodosum.

Question 23

Describe the primary disease associated with coccidioides immitis and coccidioides posadasii? How can previous exposure be determined?

Answer 23

Usually resolves without therapy; confers a strong, specific immunity to reinfection.

Previous exposure can be determined by the coccidioidin skin test.

Question 24

What happens if a patient has symtoms from coccidioides immitis and coccidioides posadasii that last more than 6 weeks?

Answer 24

They will develop 2ndary coccidioidomycosis and can have nodules, cavitary disease in lungs, or progressive pulm disease.

Dissemination to skin, soft tissue, bones, joints, and meninges.

Question 25

Who is at a higher risk for disseminated coccidioidomycosis? What is the mortality of disseminated disease if untreated?

Answer 25

Filiino, African american, native american, and hispanic people.

Men, 3rd trimester pregnancyt, immunodeficient, infants, elderly.

Mortality untreated exceeds 90%.

Question 26

What does severe coccidioidomycosis is an illness fulfilling one of the criteria for what?

Answer 26

An AIDs diagnosis.

It has been the third most life threatening opportunistic infection in AIDs patients (trailing pneumocystis and cryptococcus) occurring in up to 25% of patients in endemic areas.

Question 27

Infections due to coccidioides can be confused with what?

Answer 27

Pneomocystis.

They need to be differentiated though because coccidioides infections are treated with antifungal drugs while pneumocystis is treated with antiparasitic drugs.

Question 28

How would you diagnose coccidioides immitis and coccidioides posadasii? What is an important thing to consider when testing for this?

Answer 28

Direct visualization of endosporulating spherules.

Cultures for mold morphology will form colonies within 3-5 days.

All work should be performed in biosafety cabinet given the virulence of coccidiodes.

Question 29

What is the treatment for coccidioides immitis and coccidioides posadasii?

Answer 29

Pts with primary coccidioidomycosis do not require antifungal therapy.

Those with risk factors should be treated with antifungal agents.

Question 30

Three weeks after traveling to cali to study desert flowers, a 32 yo male develops a fever, chest pain, and sore muscles. Two days later red, tender nodules appear on his shins and his right ankle is tender and painful. A chest X-ray shows a left pleural effusion. Which organism is the likely cause of the infection?

Answer 30

Coccidioides immitis.

He was in california.