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Microbiology > Mycology and Parasitology > Flashcards

Mycology and Parasitology Flashcards

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Biology 101 flashcards
1
Q

Definition of mycology

A

Study of medically important fungi

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2
Q

Types of fungi

A

Moulds:

  • further divided into dermatophytes
  • Multicellular

Yeasts

  • unicellular
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3
Q

Dermatophyte moulds infections

A

Scalp

  • Tinea captis
  • commonest infection in paeds population
  • transfer via infected combs, towels

Nail

  • tinea unguium
  • increase with age

Feet

  • Tinea pedis

Face (males)

  • Tinea barbae

Trunk, legs arms

  • Tinea corporis

Fingernail and toenails

  • Tinea ungium

Groin

  • Tinea cruris
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4
Q

Laboratory confirmation of a dermatophyte infection

A

Microscopy

  • Interpretation of slides requires experience
  • In most cases, cannot tell what type of fungus is causing the infection

Molecular detection

  • Sensitive but more expensive than conventional methods

Culture

  • Permits species identification
  • majority identified by 7-10 days
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5
Q

Treatment for dermatophytes

A
  • Terbinafine – inhibits squalene epoxidase resulting in accumulation of squalene & the reduction of ergosterol in fungal cells = altered cell wall function & synthesis
  • Griseofulvin - binds to fungal microtubules altering mitosis & deposition of fungal cell walls
  • Itraconazole - inhibits the fungal-mediated synthesis of ergosterol via its ability to inhibit cytochrome P450
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6
Q

Non dermatophyte moulds

A
  • Aspergiullus species
  • Macroaceas noulds
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7
Q

Aspergillus mode of infection

A

Inhalation

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8
Q

Aspergiullus species and where they are found

A
  • Found in soil, plants, air
  • 200 species, only 20 cause disease
  • Most disease caused by Aspergillus fumigatus and Aspergillus flavus
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9
Q

Clinical manifestations of aspergillus infection

A

Immunocompromised

  • Widespread growth of fungus in lungs, sinuses and dissemination to other organs & CNS
  • Fever, failure to respond to broad spectum antibiotics, low grade chest pain
  • CT scans reveal lung lesions, small nodules (halo sign

Immunocompromsed

  • allergic sinusitis
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10
Q

Mucoraceous moulds species and where found?

A
  • Found in soil, on foods, air-borne
  • Affect mostly immunocompromised patients
  • Examples include Rhizopus, Absidia
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11
Q

Clinical manifestations of mucroaceous moulds

A
  • lung and nasal sinuses
  • inoculation of broken skin
  • fever, facial swelling, headache, nasal discharge, black lesions on roof of mouth,, black pus from eye
  • often lethal
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12
Q

Treatment of moulds other than dermatophytes

A
  • Amphotericin B (Ambisome) – binds to ergosterol to impair cell wall function by inducing pores causing ion leakage.
  • Itraconazole, Voriconazole, Posaconazole - inhibits the fungal-mediated synthesis of ergosterol via cytochrome P450 inhibition.
  • Caspofungin – inhibits β(1,3)-D-Glucan synthase thereby disrupting cell wall synthesis
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13
Q

Types of pathogenic yeasts

A
  • Candida species
  • Crytpococcus species
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14
Q

Yeast infection clinical features

A
  • part of normal flora
  • Colonisation in warmth and moist
  • Thrush
    • Candida albicans
  • skin infections
    • ​Malazzia species
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15
Q

Invasive candida infection features

A
  • fourth most common bloodstream infection
  • occurs in high risk patients
  • affects:
    • kidneys (80%)
    • heart (prosthetic valves)
    • gastrointestinal tract
    • lungs
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16
Q

Invasive cryptococcus infections

A
  • Pigeon droppings
    • Cryptoccocus neoformans var neoformans
  • Gum trees/ tropical regions
    • Cryptoccocus neoformans var gattii in
  • Acquired via inhalation of spores
  • commonly presents as menigitis.
  • also, productive cough, chest pain, weight loss, fever
17
Q

Laboratory identification of yeasts

A

Cultruing on chromogenic agar

  • Some yeasts have very similar colour
  • Can observe if more than one yeast is present

Maldi-tof

  • specific pattern
  • mass spec
  • 20 seconds
18
Q

Treatment of superficial candida infections

A
  • Fluconazole, itraconazole – both inhibit the fungal cytochrome P450 enzyme thus inhibiting ergosterol formation
  • Nystatin, Clotrimazole– binds to ergosterol forming ion pores which lead to leakage
19
Q

Treatment of invasive candida infections

A
  • Amphotericin B (Ambisome) – binds to ergosterol to impair cell wall function.
  • *Fluconazole
  • Caspofungin – inhibits cell wall synthesis
  • *Flucytosine – alters protein & DNA synthesis – resistance is common
20
Q

Types of parasites

A

Protozoa

  • Sporozoa - toxoplasma gondii

Helminths

  • trematodes - Shicstomatosis
21
Q

Schistosomaiasis species

A

Helminth - trematode

5 species infect humans (S species)

22
Q

Schisosome life cycle

A
  1. infected person pees in the water
  2. eggs make contact with fresh water
  3. miracicila hatches
  4. finds snail host
  5. cercaria forms
  6. penetrate skin
  7. becomes itchy
  8. go to liver and mature into schistomoluae
  9. matures with female and releases eggs
23
Q

Inital symptoms of schistomatosis

A
  • often asymptomatic
  • within 24 hours rash develops on skin
24
Q

Chronic schistomiasis (late phase) affects

A

neurological

  • eggs lodge in the CNS/brain -epilepsy

Gential

  • females get ulcerative lesions of vagina, vulca, cervix (inferitility)

hepatic

  • internal bleeding, usually sudden, massive and fatal

Intestinal

  • inflammation of the large bowel and rectum, diarrhoea

Urinary

  • ulceration of bladder, blood in urine, calcification of bladder resulting in kidney failure, bladder cancer
25
Q

Diagnosis of schistomatosis

A

1) Serology to detect egg antigens
2) Microscopy screening of stools & urine

26
Q

Treatment of Schistomatosis

A
  • Praziquantel (alters parasite membrane permeability) – paralyses the worm
  • •No side effects
  • No effect on immature worms or eggs
  • Effective for all species
27
Q

Toxoplasmosis species and life cycle

A
  1. Oocysts are shed in cat stools
  2. Intermediate hosts include birds, rodents, cattle - become infected after ingesting contaminated soil & water.
  3. Oocysts transform into tachyzoites –> bradyzoite cysts in neural and muscle tissue
28
Q

Humans become infected with toxoplasmosis by?

A
  1. eating undercooked meat of animals
  2. consuming food or water contaminated with cat stools
  3. blood trasnfusions
29
Q

Clinical features of toxoplasmosis

A

tissue cysts in skin, heart, brain, eyes

30
Q

Diagnosis of toxoplasmosis

A

Serology using ELISAs (IgG and IgM detection)

Diagnosis of congenital infections can be achieved by detecting T. gondii DNA in amniotic fluid using molecular methods such as PCR

31
Q

Treatment of toxoplasmosis

A

Pyrimethamine

Microbiology (21 decks)

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