Micro - Mycology (Opportunistic fungal infections & Others)

Question 1

What category(-ies) of infection does Candida albicans cause?

Answer 1

Systemic or superficial fungal infection

Question 2

In what 6 ways can Candida albicans present, and where applicable, in what patient populations?

Answer 2

(1) Oral and esophageal thrush in immunocompromised (neonates, steroids, diabetes, AIDS) (2) Vulvovaginitis (diabetes, use of antibiotics) (3) Diaper rash (4) Endocarditis in IV drug users (5) Disseminated candidiasis (to any organ) (6) Chronic mucocutaneous candidiasis

Question 3

How might Candida albicans infection present in immunocompromised patients? Give examples of immunocompromised patients.

Answer 3

Oral and esophageal thrush; Neonates, steroids, diabetes, AIDS

Question 4

How might Candida albicans infection present in diabetic patients?

Answer 4

(1) Oral and esophageal thrush (since immunocompromised) (2) Vulvovagnitis

Question 5

In what patient populations is Candida albicans likely to cause vulvovaginitis?

Answer 5

Diabetic, Users of antibiotics

Question 6

What condition is Candida albicans likely to cause in drug users?

Answer 6

Endocarditis

Question 7

How is Candida albicans infection treated in the following instances: (1) Vaginal (2) Oral/esophageal (3) Systemic?

Answer 7

(1) Topical azole (2) Fluconazole or Caspofungin (3) Fluconazole, Amphotericin B, or Caspofungin

Question 8

What are the morphological characteristics of Candida albicans that may appear under microscope?

Answer 8

White (hence “alba”), Dimorphic yeast (may see pseudohyphae and budding yeasts [at 20 C] or germ tubes [at 37 C])

Question 9

What are 3 ways that Aspergillus fumigatus may present, and in what patient populations and/or contexts?

Answer 9

(1) Invasive aspergillosis, especially in immunocompromised & those with chronic granulomatous disease (2) Allergic bronchopulmonary aspergillosis (ABPA): with asthma or CF (3) Aspergillomas in lung cavities, especially after TB infection

Question 10

What kind of toxins do some species of Aspergillus fumigatus produce? With what kind of cancer are such toxins associated?

Answer 10

Aflatoxins; Hepatocellular carcinoma (HCC)

Question 11

What are morphological characteristics of Aspergillus fumigatus that may be seen under microscope?

Answer 11

Not dimporphic, Septae hypae that branch at 45 degrees angle; Conidophore (specialized hyphal branch) with radiating chains of spores; Think: “ ‘A’ for Acute Angles in Aspergillus

Question 12

What disease(s)/condition(s) does Crytococcus neoformans cause?

Answer 12

(1) Crytococcal meningitis (2) Crytococcosis

Question 13

Where is Cryptococcus neoformans found in nature?

Answer 13

Found in soil, pigeon droppings

Question 14

How is Cryptococcus neoformans acquired?

Answer 14

Acquired through inhalation with hematogenous dissemination to meninges

Question 15

How is Crytococcus neoformans cultured? How is it stained?

Answer 15

Culture on Sabouraud’s agar; Stains with India ink and mucicarmine

Question 16

What is the test used for Crytococcus neoformans? What does it detect? How does it compare to culture or stain?

Answer 16

Latex agglutination test detects polysaccharide capsular antigen; More specific

Question 17

With what specific CNS finding is Crytococcus neoformans associated?

Answer 17

“Soap bubble” lesions in brain

Question 18

What are morphological characteristics of Crytocococcal meningitis that may be seen under microscope?

Answer 18

Heavily encapsulated yeast. Not dimorphic. With capsular halos and unequal budding in India ink stain

Question 19

What condition/disease do Mucor and Rhizopus fungi cause, and mostly in what patient populations?

Answer 19

Mucormycosis; Disease mostly in ketoacidotic diabetic and leukemic patients

Question 20

What is the mechanism by which Mucor and Rhizopus proliferate and dissemiante after infection?

Answer 20

Fungi proliferate in blood vessels when there is excess ketone and glucose, penetrate cribiform plate, and enter brain

Question 21

What CNS/ENT findings are associated with Mucor and Rhizopus infections?

Answer 21

Rhinocerebral, frontal lobe abscesses.

Question 22

How do Mucor and Rhizopus infections present in history or on physical exam?

Answer 22

Headache, facial pain, black necrotic eschar on face, may have cranial nerve involvement

Question 23

What are morphological characteristics of Mucor and Rhizopus that may be seen under microscope?

Answer 23

Irregular, broad, nonseptate hyphae branching at wide angles

Question 24

What condition/disease can Pneumocystis jirovecii cause? What predisposes patients to this condition/disease?

Answer 24

Causes Pneumocystis pneumonia (PCP), a diffuse interstitial pneumonia; Immunosuppression (e.g., AIDS)

Question 25

What was the original classification of Pneumocystis jirovecii? How are they classified now?

Answer 25

Protozoan; Yeast

Question 26

How is Pneumocystis jirovecii acquired?

Answer 26

Inhaled

Question 27

How do most Pneumocystis jirovecii infections present?

Answer 27

Most infections are asymptomatic

Question 28

What is PCP? How does it appear on Chest X-Ray (CXR)? How is it diagnosed (give procedure & specific finding)?

Answer 28

Pneumocystis pneumonia (caused by Pneumocystis jirovecii); Diffuse, bilateral CXR appearance; Diagnosed by lung biopsy or lavage. Disc-shaped yeast forms on methenamine silver stain of lung tissue

Question 29

How is PCP treated/managed, and in what contexts? How is it handled in HIV patients?

Answer 29

Treatment/Prophylaxis: TMP-SX, pentamidine, dapsone (prophylaxis only), atovaquone (prophylaxis only); Start prophylaxis when CD4 drops < 200 cells/mm^3 in HIV patients

Question 30

What condition/disease does Sporothrix schenckii cause?

Answer 30

Sporotrichosis

Question 31

How does Sporotrichosis present? What is typically the mechanism or method for acquiring infection?

Answer 31

When spores are traumatically introduced into the skin, typically by a thorn (“rose gardener’s” disease), causes local pustule or ulcer with nodules along draining lymphatics (ascending lymphangitis). Little systemic illness

Question 32

Why is Sporotrichosis also known as “rose gardener’s disease”?

Answer 32

When spores are traumatically introduced into the skin, typically by a thorn (“rose gardener’s” disease), causes local pustule or ulcer with nodules along draining lymphatics (ascending lymphangitis). Little systemic illness

Question 33

What pathogen causes Sporotrichosis? What are options for its treatment? What is a way to remember one of the treatments?

Answer 33

Sporothrix schenckii; Itraconazole or Potassium iodide; “plant a ROSE in the POT” (Note: Sporotrichosis = Rose gardener’s disease)

Question 34

What characterizes Sporothrix schenckii?

Answer 34

Dimorphic, cigar-shaped budding yeast that lives on vegetation