Opportunistic and Facultative Parasites

Question 1

Pneumocystis jirovecii

Answer 1

Fungus that is an important pathogen of immunocomprimised humans

Question 2

Pneumocystis lifecycle

Answer 2

Asexual: trophic forms replicate by mitosis

Sexual: haplpid form conjugate&raquo_space; cyst&raquo_space; spores

Question 3

Epidemiology of P. jirovecii

Answer 3

Host-specific = only infects humans
Transmission is airborne
Most people infected early in childhood
Mainly affects the immunocomprimised

Question 4

Diagnosis of PCP

Answer 4

Bronchoalveolar lavage (BAL)
Staining of clinical specimens

Question 5

Treatment of PCP

Answer 5

Trimethoprim-sulfamethoxazole

Question 6

Microsporidia

Answer 6

Significant cause of mortality in immunocomprimised patients
Fungi
Transmit via spores

Question 7

Species of Microsporidia

Answer 7

Enterocytozoon bieneusi

Encephalitozoon intestinalis

Question 8

Enterocytozoon bieneusi

Answer 8

Most common cause of microsporidiosis
Can cause chronic diarrhoea
Up to 11 genotypes
Does not respond well to albendazole

Question 9

Encephalitozoon intestinalis

Answer 9

Inestinal parasite, less commonly detected

Responds well to treatment with albendazole

Question 10

Encephalitozoon hellem

Answer 10

Ocular infection most common cause
Genetically diverse
Found in birds and humans
Involves the immunocompetent

Question 11

Epidemiology of Encephalitozoon spp.

Answer 11

Via faecal-oral route
Recreational water contamination
Animal reservoirs may be important, maybe airborne spores

Question 12

Diagnosis of Encephalitozoon

Answer 12

Staining specimens
Electron microscopy
Nucleic acid amplification

Question 13

Chemotherapy of Encephalitozoon

Answer 13

Albendazole (for some)

Fumagillin

Question 14

Primary amoebic meningoencephalitis (PAM)

Answer 14

Caused by Naegleria fowleri
Water contaminated with sewage
Often affects healthy young people

Question 15

Diagnosis of PAM

Answer 15

Direct examination of CSF
Antibody staining
Brain imaging
PCR

Question 16

Treatment of PAM

Answer 16

Few survivors - best treatment unknown
Amphotericin B
Miltefosine

Question 17

Granulomatous Amoebic Encephalitis (GAE)

Answer 17

Causative organisms: Acanthamoeba spp. Balamuthia mandrillaris, Sappinia pedata

Question 18

Ancanthamoeba spp.

Answer 18

Widely distributed throughout the environment
Exists as a trophozoite with long finger-like pseudopodia
Causes two diseases - GAE and Amoebic keratitis

Question 19

Diagnosis of GAE

Answer 19

Brain imaging

Biopsy specimens

Question 20

Treatment of GAE

Answer 20

Not known - miltefosine is a crucical component

Question 21

Amoebic keratitis (AK)

Answer 21

Acanthamoeba spp. infect the cornea (both trophozoites and cysts)
Occurs mainly in contact lens wearers

Question 22

Diagnosis of AK

Answer 22

Cornea scraping, staining with calcofluor or labelled antibodies
PCR

Question 23

Treatment of AK

Answer 23

Wide variety of agents used
Polyhexamethyene biguanide (PHMB), chlorhexidine gluconate and propamidine isethionate

Question 24

Balamuthia mandrillaris

Answer 24

Free living amoeba that can cause GAE
Closely related to acanthamoeba
Infects both immunocompetent/comprimised
Lives in soil

Question 25

B. mandrillaris - Peru and China

Answer 25

B. mandrillaris GAE differs in these countries from elsewhere
Present with skin lesions and much earlier before symptoms appear

Question 26

Diagnosis/treatment of BAE

Answer 26

Diagnosis = same as GAE

Most have been treated with a variety of antimicrobial drugs