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MBBS IASM > Fungi, Parasite > Flashcards

Fungi, Parasite Flashcards

1
Q

For fungi,
What is the cell wall made of

What is the cell membrane made of

Does it has a cytoplasm and nucleus?

A

Glucan, protein, Chitin

Phospholipid, ergosterol

Yes

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2
Q

What are the 3 classifications of fungi

A

Yeast, Moulds, Dimorphic fungi

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3
Q

For yeast

What’s the size

Is it unicellular/ multicellular

How does it divide

Name 2 example

A

5 micrometer in diameter

Unicellular

By budding

Candida albicans
Cryptococcus neoformans

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4
Q

For mould

What is the

Unicellular/ Multicellular

Size?

Does it form globular/ filament? What is the product formed

How does it reproduce

Name 2 subdivisions

A

Multicellular

2-4 micrometer wide

Filament. Hyphae–> Mycelium

By spore, via sexual/assexual reproduction

Aspergillus fumigatus

Dermatophytes
‐ Trichophyton, Epidermophyton, Microsporum

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5
Q

For dimorphic fungus

What determine the form

Name the forms and the criteria

Example?

A

Temperature

Yeast: 37 degree Celsius
Mould: 25 degree Celsius

Penicillium marneffei, aka Talaromyces marneffei

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6
Q

Name 3 global fungi

Name 1 local fungi

Neutropenia is the risk factor for what

HIV is the risk factor for what?

A

Candida, Dermatophytes, Aspergillus

T. marneffei

Aspergillus

C. neoformans, T. marneffei

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7
Q

What fungi causes infection/problem in immune competent host?

A

uncommon, but some can be allergic to the spores

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8
Q

What fungi causes infection in immunecompromised host?

A

Systemic candidiasis (ie by Candidas)
Cryptococcus neoformans
Aspergillus fumigatus
Talaromyctes Marneffei

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9
Q

What are the 4 classes of antifungal drug

What is their mechanism

A

Polyenes: complex with ergosterol to disrupt the fungal plasma membrane

Azole: inhibit ergosterol synthesis

Nucleoside analogues (as DNA polymerase inhibitor, reduce DNA synthesis and viral replication)

Echinocandins: Cell wall synthesis inhibitors

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10
Q

Name an example for

Polyenes

Azoles

Nucleoside analogues

Echinocandins

A

Nystatin, amphotericin B

Fluconazole, itraconazole, voriconazole,
posaconazole

5-flucytosine

Caspofungin, micafungin, anidulafungin

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11
Q

What stain do we use to visualize

Mould

Candidas

Cryptococcus neoformans

What is the method to visual ALL fungi’

What is the culture used

A

KOH

Gram Stain

Indian ink stain

Biospy (ie obtain sample)
Histopathology (ie observe sample)

Agar and broth culture

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12
Q

Name the component of cell walll that is detected in antigen testing to detect virus

What is the antigen we use for C.neoformans

What is the antigen we use for Aspergillus

Name another method to detect Aspergillus

What do we look for Patient’s response
Name a fungi that can use antibody detection

A

Beta-D-glucan

Capsular polysaccharide

galactomannan

Nucleic acid detection

Antibody detection
Biospy and histopathology

T. marneffei

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13
Q

Is Candida albican

A yeast/mould/dimorphic fungi

Name 3 important species

What is the host defense against it

A

Yeast

－C. parapsilosis
－C. tropicalis
－C. krusei

－Intact skin
－Neutrophils, monocytes

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14
Q

For Candidas albican

What is the reservior

Is it local/global?

What are the 8 risk factors for that

A

Skin, GI tract, female genital tract

Global

－Broad spectrum antibiotics:
selective pressure
－Hospitalization
－ICU
－Intravenous lines
－HIV (suppressed Immune system)
－Neutropenia (Low neutrophll count)
－Transplant (use of immune suppressor)
－Steroid (same as above)

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15
Q

What can Candidas albican cause

In immune competent host

In immunocompromised host

A

－Vaginal thrush

Refractory superficial infections
－Oral thrush
－Mucocutaneous candidiasis

Systemic candidiasis
－Candidemia: one of the major causes of nosocomial blood
stream infection
－Disseminated infection: Eye, skin, kidney
－Hepatosplenic candidiasis
－Any organ

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16
Q

How do we diagnosize the Candida albicans

By visualization?

By culture

By Antigen detection?

A

With gram stain

－Agar plates e.g. pus
－Broth culture e.g. blood
－Germ tube formation in serum, biochemical tests

Serum: -D-glucan

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17
Q

How do we treat

Superficial candidiasis

Systematic candidiasis?

A

Topical treatment (e.g. nystatin)
－Systemic treatment in refractory cases (e.g. fluconazole)

－Systemic treatment
－Fluconazole, amphotericin B

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18
Q

Why shld we prevent Candida albicans by avoid antibiotics overuse

What drug do we use to prevent? In what situation?

A

It prevents overgrowth of fungi due to disrupted flora and microbiome

Fluconazole prophylaxis for transplant recipients

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19
Q

Can we avoid exposure and do vaccination

A

No

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20
Q

What is the defintion of Parasitism

A

any reciprocal association in which a species depends upon another for its existence.

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21
Q

What is the defintion of a parasite

A

the species that derives all the benefit from the association.

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22
Q

What is the host

A

the harbouring species

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23
Q

What is the word infection and infestation in parastie

A

Infection: Invasion of endoparasites

Infestation: External parasitism by ectoparasites

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24
Q

How can we classifiy parasite according to their

Dependence on host

Temporal relationship with host

Physical relationship with host

A

obligatory (complete dependence) or facultative

temporary or permanent

ectoparasite or endoparasite

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25
Q

How can we diagnosize parasitic infecion by demostrating parasitic in appropriate specimen?

If we detect antigen/antibody in blood/other body fluid, what is it called

What parasites will we culture and is it common?

If we wanna dianosis via nucleic acid, what have to be done

A

direct microscopic examination, staining, or tissue sections

Serology

Protozoa

PCR

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26
Q

What are the 5 means to prevent parasite

A

Eliminate/reduce number of

Parasite in reservior

Vector

Avoid exposure to parasites and/or vector

Chemoprophylaxis (ie chemoprevention)

Vaccines

27
Q

How do we classify endoparasites

Name the 2 smaller groups

A

Single-celled: Protozoa

Mutlicellular: Helminths

28
Q

For Protozoa, how do we subdivide them according to the site of infection

A

Lumen-dwelling (luminal) protozoa

and Blood and tissue (extraluminal) protozoa

29
Q

For ectoparasites, what is it

A

arthropods that live in or on other animals (ie, their hosts) and obtain shelter and nourishment from them.

30
Q

Name 4 example of protozoa

A

Entamoeba histolytica
Cryptosporidium spp.
Trichomonas vaginalis
Plasmodium

31
Q

Which protozoa cause liver damage

What type of protozoa is it

What exactly does it cause

What is the infectious form and what is the active form

How does it reach the extraintestinal abscesses

A

Entamoeba histolytica

Luminal

Causes amoebic colitis/dysentery and amoebic liver abscess.

Cyst. Trophozoite

It invades the colon wall and multiplies and reach the organs via circulation

32
Q

Which protozoa cause water-borne infection

What type of protozoa is it

What exactly does it cause

A

Cryptosporidium spp.

Luminal

Causes diarrhoea in the immunocompetent hosts, but potentially severe infection in the immunocompromised individuals

33
Q

Which protozoa is the cause of common Sexual-transmitted infection

What kind of protozoa is it

Does it form cyst

What is the infectious stage of Trichomonas vaginalis

A

Trichomonas vaginalis

Luminal

No

Trophozoite

34
Q

Name the one causing Malaria

What type of protozoa is it

Name 5 main species underneath

What is the majority of case caused by

A

Plasmodium

Extraluminal

Plasmodium vivax
Plasmodium falciparum
Plasomodium malariae
Plasmodium ovale
Plasmodium knowlesi

Plasmodium vivax
Plasmodium falciparum

35
Q

For malaria, what is the

Natural Vector

Other mean of transmitting

What is the meaning of vertical transmission

A

female Anopheles mosquitoes

Blood transfusion and organ transplantation
Contaminated needles/medical instruments and medications

Mother to unborn infants before or after delivery

36
Q

What is the life cycle of Plasmodium

A

Infection.

  1. Pre-erythrocytic cycle.
  2. Erythrocytic cycle.
  3. Secondary schizogony in hepatocytes
  4. Transmission to Anopheles.
37
Q

What is the form of Plasmodium in infection

What cell will it enter? In what amount of time?

What is the vector?

A

sporozoites

Hepatocytes. Half an hour

Mosquito

38
Q

In pre-erythrocytic cycle, where are they located

What are they doing inside

A

Hepatocytes

Assexual production of exo-erythrocytic merozoites in hepatocytes. as well as infecting other hepatocytes and releasing more merozoites to blood

39
Q

What does they do in Erythrocytic cycle.

What does the term Schizogony mean

What is the term Gametogony mean

A

Invading circulating RBC

formation of merozoites in infected RBC; infection of new RBC.

Formation of male and female gametocytes (micro- and macro- gametocytes), then uptaken by female Anopheles mosquitoes

40
Q

Where is the Secondary schizogony taking place

Which 2 class will develop into what

A

In hepatocytes

P vivax and P. ovale into hypozoites

41
Q

What will the plasmodium undergoes when it is uptaken by the vector

A

The gametocytes forms the gametes

The microgametes enter the macrogametes and forms ookines then oocyst.

It will then burst to release the sporozoites

42
Q

Is there any specific symptoms for uncomplicated malaria

A

No

43
Q

For severe malaria, what happens

A

End-organ damage

44
Q

Is there any specific fever pattern for malaria

Does it always exist

A

Yes

No

45
Q

What is relapse in Malaria

A

recurrence of symptoms after
complete initial clearing of
parasitaemia due to re- invasion of
bloodstream by exo-erythrocytic
stages (hypnozoites).

46
Q

What is recrudescence in Malaria

A

recurrence of
symptoms after initial parasitaemia
is reduced to a very low level but
not completely cleared.

47
Q

What is the pathogenesis, in other words, how does it cause problem for Malaria

A
  1. Increased destruction of erythrocytes due to:
    * Decreased deformability of RBC.
    * Infection by parasites (P. falciparum infects both reticulocytes and mature RBCs)
    * Increased clearance in splenomegaly.
  2. Cytoadherence in P. falciparum infection (adhesion of infected RBC to endothelial cells) resulting in microvascular obstrucon.
  3. Lysis of RBC resulting in iron depletion, anaemia, haemoglobinuria (hence the name of blackwater fever)
  4. Immune complex deposition in kidneys resulting in nephrotic syndrome (in chronic
    infections due to P. malariae).
  5. Release of inflammatory cytokines during the course of infection.
48
Q

What is the most severe form of Malaria

What are it’s characteristics

A

Falciparum malaria

Invades RBC of all ages.
* High levels of parasitaemia.
* Highest mortality.
* Microvascular obstruction.

49
Q

What shld we ask when suspecting malaria

A

Travel history

50
Q

Name 3 therapy for malaria and their underlying principle

A

chemoprophylaxis: destroys asexual erythrocytic stages to prevent development of clinical symptoms.

**Preventive measure

Clincal cure: blood schizonticidal
–> Killing infected RBC at all stages

Radical cure:Tissue schizonticide
–> targets at elimination of the gametocytes and hepatic resting
stages (hypnozoites of P. vivax and P. ovale)

51
Q

Can chemoprophylaxis protect malaria completely?

When shld the antimalarials be intaken

A

No

Before, during and some days after going to an endemic place

52
Q

What is the 5 methods to prevent and control malaria

A
  1. Vector control; e.g. reducing breeding sites of mosquitoes.
  2. Avoidance of exposure; e.g. use of insect repellents.
  3. Treatment of cases
  4. Chemoprophylaxis
  5. Vaccines are now available, but they do not confer 100% protective efficacy,
    and currently not used for general protection of the whole population or
    travellers.
53
Q

What are the symptoms of malaria

A
  1. Paroxysms.
    * Chills and rigor for 1–2 hours, followed by spiking fever in the next few hours.
    * Marked sweatng and defervescence with a rapid drop in temperature.
    * Note that in real life, patients usually do not present with the typical periodic fever paterns.
  2. Severe malaria (usually in P. falciparum, and occasionally P. vivax): characterized by end organ damage, e.g. cerebral malaria, severe anaemia, renal failure, circulatory shock, hypoglycaemia, etc.
54
Q

What is the fever pattern of malaria theoretically

A
  • P. vivax, P. ovale, P. falciparum: 48-hour cycle.
  • P. malariae: 72-hour cycle.
  • P. knowlesi: 24-hour cycle.
55
Q

How can we diagnosize Malaria

A
  1. History: travel history, fever patern (not useful in most clinical cases), prophylaxis taken, blood or blood product transfusion, etc..
  2. Specimens: peripheral blood, an􀆟coagulated with EDTA.
  3. Thick and thin blood films stained with Giemsa, Wright, or Field’s stain.
  4. Single nega􀆟ve blood smear does not rule out malaria.
  5. Other diagnos􀆟c tests: an􀆟gen detec􀆟on in peripheral blood, nucleic acid amplifica􀆟on
56
Q

For Helminths, what are the 3 subdivisions

A

nematodes, trematodes, cestodes

57
Q

What is nematodes

What can it be subdivided into

A

Round worms

Intestinal nematodes and blood and tissue nematodes

58
Q

Which one is usually asymptomatic for immunocompetent host but cause problem for immunocompromised host

What problem can it cause

What can cause complication

What type of nematodes is it

Why will it cause pneumonia

A

Strongyloides stercoralis

Hyperinfection and disseminated infection (infection due to a far away origin)

bacterial sepsis

Intestinal nematodes

It brings bacteria from the large intestine to the lungs

59
Q

Which nematode is common in cosmopolitan infection

What does it cause

What form is it intaken

How does it cause the symptom

A

Enterobius vermicularis

perianal pruritis

embryonated egg

At night, the female Enterobius vermocularis will travel to perianal region to lay eggs

The movement

60
Q

What Nematode cause meningitis

Where is it usually present

Where is it present before it infects human

How does it leave the first host

What is the role of the snails and slugs. etc

A

Angiostrongylus cantonensis

Present in high risk food raw or undercooked snails and slugs, freshwater shrimp, land crabs,

Lung of rodents

Faeces of rodents

Intermediate host

61
Q

What is meant by trematodes

What is their characteristic

How do we classify them

What are the 4 divisions

A

Flukes. Leaf-shaped worms

All require freshwater snail as intermediate host

By the organ of involvement

Liver flukes, intestinal fluke, lung fluke, blood fluke

62
Q

What is most common endoparasite in Hong Kong

What type of fluke is it

What cancer is it related to

What are the life stages

A

Clonorchis (Opisthrochis) sinensis

Liver fluke

cholangiocarcinoma (bile duct cancer)

  1. Ingested by Snails in the form of egg
  2. Grow into miracidia–> sporocyst –> Redia –>cercaria
  3. Cercaria penetrate under the scale of fish
    and become metacercaria
  4. It forms excyst in duodenum and goes to bile duct to f=become adult
  5. Lay embryonated egg that is found in faeces
63
Q

What trematode is related with pneumonia

What are the life stages of the parasite

What is it’s route in human body

A

Paragonimus spp.

In snail:
embryonated egg–> Miracidium –>Sporocyst –> Redia –> Cercaria –>metacercaria –>Excyst in stomach

Stomach –> Intestinal wall –> Abdominal cavity –> Penetrates diaphragm
–>Pleural cavity

64
Q
A

MBBS IASM (23 decks)

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