Lecture 05 - Amoebae

Question 1

What genus of amoeba are potentially pathogenic to humans

Answer 1

acanthamoeba, naegleria, balamuthia, sappinia and hartmannella

Question 2

What is the group name of amoebae

Answer 2

sarcodina

Question 3

What infections can amoebae cause

Answer 3

eye, brain, and other tissues/organs

Question 4

What are the two basic forms of amoebae

Answer 4

trophozoite and cyst

Question 5

What is the purpose of encystment

Answer 5

occurs under adverse environmental conditions and allows for survival outside of a host

Question 6

What are the key points about trophozoites

Answer 6

• adhesion essential for locomotion and feeding
• movement enhanced by higher temperatures

Question 7

What are amoebastomes

Answer 7

no correlation with pathogenicity, can attach to surfaces, ingests bacteria and cell debris

Question 8

What are the key points about the flagellated stage

Answer 8

• cell changes shape
• induced by nutritional deprivation, temperature, or osmotic shock
• lasts from 2 to several hours

Question 9

What are the key points about the cyst stage

Answer 9

• environmentally hardy
• mucopolysaccharide double wall
• resistant to biocides
• ostioles sealed by mucus plugs
• cysts not formed in tissues, left behind when trophozoites emerge

Question 10

What is a diphasic amoeba

Answer 10

exists in both ameboid and flagellate form

Question 11

How do amoeba invade

Answer 11

via the nasal passages on contact with water, they then travel along olfactory nerves, cribriform plate to brain

Question 12

What does virulence of amoeba depend on

Answer 12

• Nfa 1 protien
• feeding cups
• nitric oxide production
• pore-forming proteins
• cytolytic molecules (cysteine proteases, phospholipases, hospholipolytic enzymes)

Question 13

What is primary amoebic meningoencephalitis

Answer 13

extensive cell necrosis leading to significant hemmorage, destruction of meninges, olfactory nerves and brain tissue. As well as inflammatory exudate, and edema leading to death

Question 14

What is the epidemiology of amoeba

Answer 14

ubiquitous and found mostly in freshwater lakes, hot water springs, poorly chlorinated pools and thermally polluted water bodies worldwide

Question 15

How does the lab diagnose amoeba

Answer 15

microscopy of brain biopsy, CSF
in vitro culture
PCR

Question 16

What is acanthamoeba culbertsoni

Answer 16

a trophozoite that has a spine and thick psudopodia, can also exist as as double walled cyst

Question 17

What is the pathogenesis of acanthamoeba culbertsoni

Answer 17

slow tissue invasion

adhesion via mannose binding proteins

destruction of corneal eithelium

breaching bowmans capsule and destruction of corneal stroma

Question 18

What is the pathology of acanthamoeba culbertsoni

Answer 18

granulomatous amebic encephalitits, necrotizing lesions, eye lesions, granuloma formation

Question 19

What is the clinical presentaion of acanthamoeba culbertsoni

Answer 19

granulomatous amoebic encephalitis, healthy host with compromised eye, acute/chronic infection of skin, lung, uterus, prostate in immunocompromised

Question 20

What is the epidemiology of acanthamoeba culbertsoni

Answer 20

free living and widely distributed in natural waters as well as in dust and soil

also detected in bottled mineral water, jacuzzis, recreational pools, ventilation ducts, humidifiers, air-conditioning units, shower heads and taps

Question 21

How does the lab diagnose acanthamoeba culbertsoni

Answer 21

CSF, corneal scrapings, brain skin and other biopsies, microscopy using permanent stain, in vitro culture, PCR

Question 22

What separates balamuthia mandrillaris from acanthamoeba culbertsoni

Answer 22

disseminated infection