Opportunistic + Facultative Pathogens

Question 1

what is this?

Answer 1

Pneumocystis trophozoites on Giemsa stain

Question 2

what is this?

Answer 2

Pneumocystis cysts on Grocott silver stain.

Question 3

Name the organism responsible for Pneumocystosis pneumonia

Answer 3

Pneumocystis jirovecii

Question 4

what happens with PCP at organism and cell level in the lung?

Answer 4

organism adheres to type 1 pneumocytes lining alveoli which then makes it harder for oxygen to get into.

Question 5

How is PCP spread?

Answer 5

person to person through the air - however some healthy adults can carry pneumocystis fungus in the lungs without having symptoms and it can spread to other people with weakened immune systems such as HIV/AIDS patients, solid organ or stem transplant patients, etc.

Question 6

How do you diagnose PCP?

Answer 6

Bronchoalveolar lavage collection or lung biopsy. often sample sent to the lab for PCR + staining. Blood test to detect B-D glucan (beta-D glucan - part of the cell wall of many different types of fungi) can also help diagnose PCP.

Question 7

what is wrong with ONLY doing a serum (1,3)-B-D-Glucan test?

Answer 7

1. sensitivity is high but not as good as PCR - used alone, about 11% patients would be missed.
2. Specificity - the same polysaccharide is present in the cell walls of other fungi and can be present in the serum of patients who have received various therapeutic products and procedures.

Question 8

What is the first line treatment for PCP?

Answer 8

Co-trimoxazole ( trimethoprim/sulfamethoxazole)

Question 9

Apart from first line PCP treatment, what other drugs can be used to treat?

Answer 9

Pentamidine, Dapsone-trimethoprim, Clindamycin-primaquine, Atovaquone. Also Echinocandins.

Question 10

Name 2 microsporidia that can infect immunocompromised patients.

Answer 10

Enterocytozoon bieneusi and Encephalitozoon intestinalis.

Question 11

What is the most common cause of intestinal microsporidia in immunocompromised patients?

Answer 11

Enterocytozoon bieneusi

Question 12

What main symptoms do Enterocytozoon bieneusi cause?

Answer 12

chronic diarrhoea

Question 13

what organism possesses the smallest nuclear genome of any cell?

Answer 13

Question 14

Name the organism causing microsporidial keratitis especially in the immunocompetent or even rugby players sliding along the mud.

Answer 14

Encephalitozoon hellem.

Question 15

name transmission routes of intestinal microsporidiosis.

Answer 15

Faecal oral route(recreational water and waterborne outbreaks), possible animal reservoir and need to think about airborne spores.

Question 16

what drug is used to treat Encephalitozoon intestinalis and describe its mechanism.

Answer 16

albendazole by inhibiting the polymerisation of spindle microtubule tubules.

Question 17

name the organism that can cause primary amoebic meningoencephalitis.

Answer 17

Naegleria Fowleri

Question 18

How do you diagnose n.fowleri?

Answer 18

direct examination of CST through staining and culture.

Question 19

what is the arrow pointing at?

Answer 19

Naegleria fowler trophozoite in CSF

Question 20

how do you treat primary amoebic meningoencephalitis? (PAM)

Answer 20

Amphotericin B

Question 21

how do you develop P.A.M

Answer 21

swimming, playing, diving and washing in infected water whereby the bacterium enters the nasal sinuses entering the brain via the olfactory nerve tract.

Question 22

name the organisms causing granulomatous amoebic encephalitis ( G.A.E)

Answer 22

acanthamoeba, balamuthia mandrillaris, sappinia pedata.

Question 23

what two diseases do acanthamoeba app cause?

Answer 23

Granulomatous amoebic encephalitis(exclusive mainly to immunocompromised) and amoebic keratitis.

Question 24

what is different about G.A.E tissue compared to E.histolytica?

Answer 24

both trophozoites and cysts are found in the tissues.

Question 25

what is this?

Answer 25

acanthamoeba cyst in GAE brain tissue. (note mostly diagnosed at post mortem)

Question 26

what is this?

Answer 26

acanthamoeba trophozoite in cornea.

Question 27

what causes amoebic keratitis?

Answer 27

acanthamoeba in corneal tissue.

Question 28

how do you treat amoebic keratitis

Answer 28

usually a trio of polyhexamethyene biguanide (PHMB), chlorhexidine gluconate with propamidine isethionate. this disease often caused by contact lens wearers washing their lenses in tap water - THINK OF CELINE IN MELBOURNE> apply initially every hour for 48hrs (eye drops)