Microbiology 3.11 Flashcards Preview

NMSK-B III > Microbiology 3.11 > Flashcards

Flashcards in Microbiology 3.11 Deck (64):
1

What is the subacute onset of symptoms for chronic meningitis?

-fever
-headache
-vomiting

-may lead to CN palsies

2

What are more progressed symptoms of chronic meningitis?

-seizure
-mental status change
-confusion
-hallucination
-focal neurologic deficits

3

What are the common etiologies of chronic meningitis?

Mycobacterium tuberculosis (mycobacterial)
Cryptococcus neoformans (fungal)

4

What are the clues to etiology for diagnosing chronic meningitis?

-travel
-+ TB test or TB exposure
-immune status
-sexual history
-injection drug use
-contact with ticks, cats, wild game

5

What is a brain abcess?

rare focal, intracerebral infection

6

How does a brain abcess begin?

localized areas of cerebritis which develops into collection of pus surrounded by well-vascularized capsule filled with live and dead microorganisms

7

What causes the hematogenous seeding of brain abcesses?

-endocarditis; usually leads to multiple abcesses

-direct spread from otitis media, mastoiditis, sinusitis, dental infeciton

-local injury, neurosurgery

8

What does the etiology of brain abcesses depend on?

-age
-site of primary infection
-immune status
-season
-geographic location

9

What are the clinical symptoms of a brain abcess?

-*headache*
-may have low grade fever
-neurologic symptoms as lesion expands

10

What are the common etiologies of a bran abcess in the immunocompetent?

-strict and facultative anaerobes; mixed infection
-Gr- bacilli [K. pneumoniae, E. coli, P. aeruginosa, and Proteus]
-viridans streptococci
-S. aureus [and coag - staph]
-bacteroides

11

What are the common etiologies of a bran abcess in the immunocompromised?

-Toxoplasma gondii
-Cryptococcus neoformans
single infection

12

What are the common etiologies of a brain abcess in immigrants?

Taenia solium (parasite)

13

What are the CSF findings for viral/mycobacterial infections?

Increased:
-protein
-WBC [PMNs, lymphocytes]
-acid-fast + organisms

No/Normal:
-opening pressure
-clarity [spider's web clot over time}

Decreased:
-glucose

14

What are the CSF findings for fungal infections?

Increased:
-opening pressure
-protein
-WBC [fungal lymphocytes]
-India ink staining + organisms

No/Normal:
-clarity {spider's web clot over time]

Decreased:
-glucose

15

What do Cryptococcus look like on a plate?

-oval
-budding yeast
-surrounded by *wide* polysaccharide capsules

16

Where can Cryptococcus neoformans be found and who does it infect?

-grows in soil contaminated with bird droppings [pigeons]
-does not infect birds
-found worldwide
-infects immunocompromised

17

Where can Cryptococcus gattii be found and who does it infect?

-grows in soil around eucalyptus trees (gum trees)
-found in Pacific NW
-infects immunocompetent

18

How is Cryptococcus transmitted?

-inhalation of yeast cells (desiccated) of basidiospores
-*no human-to-human transmission*

19

What is the disease manifestation of a Cryptococcus infection?

-primary infection of lungs
-hematogenous spread to meninges, skin, bone

20

What is the clinical presentation of chronic meningitis caused by Cryptococcus?

-headache
-stiff neck
-seizures
-disorientaiton

21

What is a cryptococcoma?

granuloma caused by Cryptococcus gattii, typically found in healthy, immunocompetnet people

22

What is the life cycle of Cryptococcus?

1) avian feces or trees to
2) lungs via inhalation
3) phagocytosis by alveolar *macrophages*
4) disseminate to CNS [or go latent or resolve]

23

What are the virulence factors for Cryptococcus?

polysaccharide capsule

melanin

24

What is the function of the polysaccharide capsule in terms of virulence?

-prevents phagocytosis
-allows survival in macrophage if needed

25

What is the function of melanin in terms of virulence?

-dark pigment in cell wall
-protects against oxidative killing
-made by phenol oxidase

26

How are Cryptococcus infections diagnosed using CSF?

-CrAg [Cryptococcal capsule antigen} testing
-CSF culture [latex agglutination, lateral flow assay (LFA)]
-India ink stain of CSF ($)

27

How are Cryptococcus infections diagnosed using imaging?

MRI/CT to identify Cryptococcal lesions

28

How are Cryptococcus infections diagnosed using plate assays?

-white, mucoid colonies on Sabouraud dextrose agar [takes a lot of time]
-histopathic

29

How are Cryptococcus infections treated?

antifungals
1) amphotericin B and flucytosin [induction therapy]
2) fluconazole [suppression of cryptococcosis]

30

What is IRIS?

-immune reconstitution inflammatory syndrome; HIV-infected pt given highly active antiretroviral therapy (HAART) due to sudden increase in CD4+ cells
-increases inflammatory response to fungal infection
-may result in death
**suggested to start treatment for cryptococcal infection first

31

What are cestodes?

tapeworms

32

What is the life cycle of cestodes?

1) humans ingest tissue cysts in uncooked meat
2) parasite hatches in intestine
3) parasite matures into intestinal tapeworm
4) proglottids containing eggs released in feces
5) eggs survive in fecal-contaminated soil
6) ingested viable eggs eaten by animal reservoir, hatch, larvae produce tissue cysts to complete cycle

33

What are the main diseases caused by Taenia solium?

Taeniasis
-adult tapeworm in small intestines

Cysticercosis
-larvae develop in eyes, muscles, or brain

34

What are the host and intermediate host of Taenia solium?

host: humans
-sexual reproduction

intermediate host: swine (& humans)
-asexual/larval development

35

What are the risk factors of contracting a Taenia solium infection?

-access of pigs to human feces
-consumption of raw/under-cooked pork
-endemic in Asia (China), S. America (Mexico), Africa

36

What is the life cycle of Taenia solium in pigs?

1) eggs from human feces are ingested by pigs
2) eggs hatch, release hexacanth embryo, penetrates intestinal wall
3) lymphohematogenous system used to reach any tissue
4) develops into 1-cm shite cysticercus (cyst) where it can stay up to 5 yrs.

37

How does Taeniasis occur?

1) humans consume under-cooked or raw pork containing cysts
2) scolex everts in jejunum and attaches to mucosa; develops into adult worm
3) adult worm produces lots of eggs which release into human feces
4) usually asymptomatic, but cause abdominal pain, loss of apetite, weight loss, upset stomach, diarrhea

38

How is Taeniasis diagnosed?

visualizing (15-20 uterine branches) proglottis in stools or eggs

39

What is the treatment for Taeniasis?

antiparasitic (praziquantel)

40

What are prevention strategies for Taeniasis?

-cook pork adequately
-dispose waste properly so pigs cannot ingest human feces

41

What is cysticercosis?

larval infection

42

What is the life cycle of a cysticercosis?

1) human with taeniasis defecates (feces)
2) food or water contaminated with the feces
3) ingestion of eggs from contaminated food or water
4) larvae hatch in the intestine and cross mucosa
5) larvae enter bloodstream
6) larvae encyst in deep tissues as cysticerci
**or auto-infection (direct fecal-oral or vomiting)

43

What is prevention for cysticercosis larval infections?

-treat patients to prevent autoinfection/carrier state
-observation of proper hygiene

44

How does cysticercosis affect the muscles?

infection of muscles occurs and commonly results in subcutaneous nodules

45

How does cysticercosis affect the eyes?

eye infections may casue:
-uveitis
-retinitis
-larvae can be visualized floating in the vitreous

46

How does cysticercosis affect the brain?

brain infections (neurocystiverosis) may lead to:
-headaches
-vomiting
-seizures
-focal neurological deficits
-mental disturbances
-hydrocephalus
-death

47

What is the most common cause of acquired epilepsy in the developing world?

cysticercosis brain infection from Taenia solium

48

How is cysticercosis diagnosed?

presence of cyst in the tissue, usually by surgical removal or CT scan/MRI

49

What is the treatment of cysticercosis?

antiparasitic (praziquantel)

anti-inflammatory (corticosteroid)

potentially surgery

**no antiparasitic drugs for calcified (dead) cysts but may need anti-seizure meds

50

What is a protozoan trophozoite?

active form which grows and replicates by binary fission within the host

51

What is a protozoan cyst?

dormant, non-replicating form which is adapted for survival in various environmental extremes as it transits between hosts
**has double membrane

52

What is the locomotion of protozoan?

gliding motility (apicomplexa) = sporozoa

53

What are the basics of Toxoplasma gondii?

-sporozoan = obligate intracellular parasite
-alternating cycles of sexual and asexual reproduction

54

What are the definitive and intermediate hosts, and dead-ends of Toxoplasma gondii?

definitive host: domesticated host; sexual reproduction

intermediate host: humans and warm-blooded animals [mammals, birds]; asexual reproduction

dead end: human infections

55

What are the major morphologic forms of Toxoplasma gondii?

1) tachyzoite
-rapidly dividing and invasive
-type of ttrophozoite
-fragile and short-lived
-may be intracellular

2) bradyzoite
-slowly-dividing
-in tissue cysts
-infectious as long as meat is edible and uncooked

3) sporozoite protected inside oocyst
-resistive to environmental [warm, moist soil]

56

What is the life cycle of Toxoplasma gondii?

1) intermediate host ingests tissue cysts or oocysts
2) cysts disseminate to extraintestinal tissues
3) multiply within macrophage and are released as tachyzoites
4) released tachyzoites enter new cells
5) "resting" bradyzoites form withn tissue cysts
6) trophozoites undergo schizogony
7) epithelial cells eventually differentiate into gametocytes
8) fusion of mature male and female gametes leads to formation of an oval, thick-walled oocyst
9) oocyst is excreted in feces and sporulates in teh environment

57

How is Toxoplasma gondii transmitted to humans?

-ingest sporulated oocysts from cat feces
-ingest of tissue cysts in meat [esp. pork]***
-congenital (tachyzoites)
-transfusion/organ transplantation (rare)

58

Who is most commonly infected by Toxoplasma gondii?

old people; highest in older than 70 y/o

59

What is toxoplasmosis?

-Toxoplasma gondii infection
-highly lethal infection of immunocompromised due to dissemination to various tissues
**esp. neurologic involvement

60

How does toxoplasmosis present in a healthy person?

-usually asymptomatic
-may cause self-limited mononucleosis-like disease w/:

-lymphadenopathy
-fever

61

How does congenital toxoplasmosis occur?

-eating undercoked meat during pregnancy
-seroconversion!!
-also avoid changing litter box during pregnancy [make spouse do it daily since it takes days for these to grow]

62

How is toxoplasmosis diagnosed?

-serology
-detection of taxoplasmic-specific IgG, IgM, IgA antibodies
-tissue stain from CSF
-PCR of amniotic fluid (congenital)
-contrast CT shows lesions

63

What are prevention strategies for toxoplasmosis?

-avoid contact with cat feces
-wash soil-contaminated vegetables/fruits
-avoid undercooked/raw meat
-wash hands

64

What is the second leading cause of death from food-borne illness in the US?

toxoplasmosis

(Listeria is #1)