MI: Fungal Infections Pt.1

Question 1

List three examples of:

• Yeast
• Moulds

Answer 1

Yeasts: single-celled, reproduce by budding

• Candida
• Cryptococcus
• Histoplasma (dimorphic)

Moulds: multicellular hyphae, reproduce by branching + extension

• Aspergillus
• Dermatophytes
• Agents of mucormycosis

Question 2

What does ‘dimorphic’ mean with regards to fungi?

Answer 2

It can change between being a yeast and a mould

Question 3

Describe the appearance of Candida under the microscope.

Answer 3

• Single-celled organisms that replicated by budding
• They are much bigger than bacteria

Question 4

Which systemic infections can be caused by Candida?

Answer 4

Septicaemia, endocarditis, meningitis

Question 5

List some patient groups that are at risk of invasive Candida infection.

Answer 5

• VLBW infants
• Immunocompromised
• Patients on ITU (especially if they have lines in)
• Patients receiving TPN
• Immunocompotent patients who have had antibiotic treatment

Question 6

List some agents that can cause candidiasis.

Answer 6

• Candida albicans (MOST COMMON)
• Candida glabrata
• Candida krusei
• Candida tropicalis

Question 7

Describe a screening test for candidiasis.

Answer 7

• Candida albicans forms a germ tube
• Can be identified by microscopy

Question 8

How can Candida affect the eyes?

Answer 8

Causes endophthalmitis

Question 9

What does generalised candidiasis in babies usually occur secondary to?

Answer 9

Seborrheic dermatitis

Question 10

What is the term used to describe candidiasis of babies that afects the skin folds?

Answer 10

Intertrigo

Question 11

How can candidiasis lead to mediastinitis?

Answer 11

If oesophageal candidiasis invades the tissue leading to perforation

Question 12

Outline the diagnostic tests used for candidiasis.

Answer 12

• Swabs (smeared on KOH)
• Bloods
  
  • Beta-D glucan blood test
  • Antigen + serology (mannan, anti-mannan)
  • DNA PCR
• Blood/tissue cultures
• Imaging
• Endoscopy

Question 13

What type of agar is needed for culturing Candida?

Answer 13

Sabouraud agar - impregnated with antibiotics to prevent bacteria from outcompeteing the fungi

Question 14

Outline the management of candidiasis.

Answer 14

• At least 2 weeks of antifungals after the last negative culture
• Echo and fundoscopy to look for endocarditis/endophthalmitis
• Echinocandins - empirical for non-albicans infections
• Fluconazole - empirical for Candida albicans

Question 15

What type of disease does Cryptococcus tend to cause?

Answer 15

Pulmonary, systemic and meningitic disease

Question 16

Which group of antifungals is Cryptococcus inherently resistant to?

Answer 16

Echinocandins

Question 17

What is the treatment of choice for Cryptococcus infection?

Answer 17

Ambisome (amphotericin B)

Question 18

What is the main aetiological organism in cryptococcosis.

Answer 18

Cryptococcus neoformans

Question 19

Which patients are particularly at risk of cryptococcosis?

Answer 19

• Impaired T cell immunity (AIDS)
• Solid organ transplant patients on T Cell immunosuppressants

Question 20

What is Cryptococcus neoformans var. gatii?

Answer 20

• Causes meningitis in apparently immunocompetent individuals in tropical countries
• High incidence of space-occupying lesions in the lung and brain
• Increasing resistance to amphotericin B

Question 21

Describe the appearance of Cryptococcus under the microscope.

Answer 21

• Distinc capsule around the yeast
• India ink can be used to stain

NOTE: the capsule is not always present

Question 22

Which diagnostic test is important in the diagnosis of cryptococcosis?

Answer 22

Enzyme immunoassay (EIA) looking for components of the capsule

Question 23

Why might a lumbar puncture be negative in cryptococcal meningitis?

Answer 23

Cryptococcal meningitis can cause hydrocephalus which prevents the circulation of CSF meaning that the sample taken at LP may not have been exposed to CSF within other parts of the ventricular system

Question 24

Outline the treatment options for Cryptococcus infection.

Answer 24

• 3 weeks amphotericin B (ambisome) +/- flucytosine
• Repeat LP for pressure measurement
• Secondary suppression - fluconazole

Question 25

List the diseases that can be caused by Aspergillus.

Answer 25

• Mycotoxicosis (ingestion contaminated foods)
• Allergic bronchopulmonary aspergillosis
• Aspergilloma (colonising pre-formed cavities)
• Invasive/disseminated disease