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MCD Microbiology > 9 Fungal Infection > Flashcards

9 Fungal Infection Flashcards

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Biology 101 flashcards
1
Q

Q: What are fungi? Genetics? (2) Similarities to us? meaning? (2) Give an example of an important fungi.

A

A: a kingdom part of the eukaryotic crown group

  • several chromosomes
  • massive complex genome

-similar metabolism- so anything that works on yeast is likely to have a similar effect on us (difficult to work with them as pathgens)

saccharomyces cerevisiae (brewers yeast)

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2
Q

Q: How can the fungi group further divide? (2) Describe each.

A

A: into 2 phyla

  • Basidiomycota: consists of many of the mushrooms that we find
  • Ascomycota: moulds, contains 90% of all human fungal infections
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3
Q

Q: Out of the Basidiomycota, which fungus causes the largest burden of disease? Disease? Mechanism? (2)

A

A: Cryptococcus neoformans -> causes CRYPTOCOCCAL MENINGITIS which is a form of minigitis in people with AIDS

  1. These cryptococci can be inhaled into the lungs - alveolar macrophages are usually good at mopping up fungal cells as we inhale them
  2. Cryptococcus can get into the brain (a sugar rich environment) and cause meningitis
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4
Q

Q: Name 2 fungi in the phyla Ascomycota and their corresponding diseases.

A

A: aspergillus fumigatus
-invasive pulmonary aspergillosis

candida albicans
-blood stream infections

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5
Q

Q: Describe fungi in terms of pathogenic behaviour.

A

A: most fungal infections are opportunistic - live in environment without the need for us - but are ready to take possession of our organism whenever it presents a vulnerable point or a point of weak resisting power

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6
Q

Q: Every lung full of air we breath in is? What do we need to do?

A

A: filled with fungal spores

-ensure they get removed otherwise they could digest away at lung or even get into blood

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7
Q

Q: How do fungi digest their food? How? Name?

A

A: extracellularly (effectively suspended in its food source)

  • produce hydrolytic enzymes which are pumped out into the environment
  • said substances= powerful polymer degrading substances which rot the material around them

SAPROPHYTES

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8
Q

Q: What do fungi produce in terms of reproduction? Air sample? What happens?

A

A: -produce a large number of spores

  • contained as many as 200,000 spores per m^3
  • dispersed over large distances
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9
Q

Q: What type of fungi are transmitted via contact? (2)

A

A: commensal organism and skin colonisers

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10
Q

Q: What are the 3 classes of fungal disease?

A

A: 1. allergies

  1. mycotoxicoses
  2. mycoses= active disease causing agent = 3 types
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11
Q

Q: Describe fungal allergies. Examples (4).

A

A: inhalation/contact with fungal spores may induce wide range of allergic diseases

  • Rhinitis
  • Dermatitis
  • Asthma
  • Allergic Broncho-Pulmonary Aspergillosis (ABPA)
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12
Q

Q: What is Allergic Broncho-Pulmonary Aspergillosis (ABPA) caused by? Where does it thrive? Occurs in what percentage of asthmatics?

A

A: Aspergillus fumigatus

  • grows in compost and likes high heat including our body temperature
  • 2.5%
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13
Q

Q: What are mycotoxins? What do they cause? Symptoms? (6) Therapy? (2)

A

A: secondary metabolites of moulds that exert toxic effects on animals and humans (important in defending fungi)

cause mycotoxicoses= toxic reaction caused by inhalation or indigestion of mycotoxins

  • breathing problems
  • dizziness
  • severe vomiting
  • diahorrea
  • dehydration
  • hepatic and renal failure 6 days later
  • gastric lavage and charcoal
  • liver transplant
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14
Q

Q: Give an example of a non lethal mycotoxin. What does it cause? Treatment?

A

A: Psilocybin produced by Psilocybe semilanceata => a trip/sought after effects

  • visual distortions of colour, depth, form
  • progressing to visual hallucinations

time

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15
Q

Q: Give an example of a lethal mycotoxin. Produced by? Nature? Growth? Effect? (2) Increased risk?

A

A: AFLATOXIN produced by Aspergillus flavus is the most carcinogenic natural compound known

Contaminates grain

If you get aflatoxin poisoning and you have liver damage from hepatitis B then you are at particular risk of cancer

South-East Asia - higher rates of liver cancer possibly due to greater exposure to aflatoxin (consistent low levels of exposure)

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16
Q

Q: What are mycoses? Types? (4)

A

A: disease caused by fungi which is classified by the level of tissue affected (superficial, cutaneous, subcutaneous, systemic)

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17
Q

Q: What are superficial mycoses? Host response?

A

A: common and occurs on keratin rich tissue (skin or hair shaft)

No living tissue is invaded - no cellular response from host

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18
Q

Q: Give an example of a superficial mycoses. Causes? Treatment?

A

A: Malassezia globosa

  • produces oleic acid which causes inflammation of stratum corneum and ‘dandruff’
  • selenium sulfide inhibits fungal growth (doesn’t kill)
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19
Q

Q: What is cutaneous mycoses also called? Caused by? Result? (3) 5 examples.

A

A: -dermatophytocis and dermatomycosis
-dermatophytes or keratinophilic fungi

  • Produce keratinases which are capable of hydrolysing keratin
  • Inflammation is caused by host response to metabolic by-products
  • Tinea - latin for ring worm (phenotype)
  1. tinea capitis (head/neck)
  2. tinea pedis (athletes foot)
  3. tinea corporis (body)
  4. tinea cruris (groin= jock itch)
  5. tinea unguium (finger/toe nails)
20
Q

Q: What is tinea capitis? Affects?

A

A: cutaneous mycoses/ ringworm of scalp, eyebrows and eye lashes with a propensity for attacking hair shafts and follicles

25% chn in schools over africa (disfiguring)

21
Q

Q: What is the most paediatric dermatophyte infection?

A

A: tinea capitis

22
Q

Q: What is tinea pedis? Caused by? What proportion of the population will be infected with it at some point?

A

A: Incredibly infectious cutaneous mycoses/ athletes foot
-Trichophyton rubrum

70%

23
Q

Q: What is the worlds most prevalent dermatophyte?

A

A: Trichophyton rubrum which causes athletes foot

24
Q

Q: What is tinea corporis also known as? What is it? Treatment? (3)

A

A: ring worm
-cutaneous mycoses

antifungal creams:
-miconazole
-clotrimazole
orally
-griseofulvin = systemic antifungal
25
Q

Q: What is subcutaneous mycoses? Occurrence? Treatment? 3 examples.

A

A: chronic, localised infections of the skin and subcutaneous tissue following traumatic implantations of the aetilogic agent (including stratum corneum)

  • rare
  • seen in combat blast related wounds

often very hard to treat- amputation is the usual option

  1. Sporotrichosis
  2. Chromoblastomycosis
  3. Mycetoma
26
Q

Q: What is Mycetoma?

A

A: chronic infection of the skin, subcutaneous tissue and sometimes bone, characterised by discharging sinuses filled with organisms

27
Q

Q: What is Sporothrix schenckii and what does it cause? Epidemic?

A

A: fungi that causes subcutaneous mycoses= sporotrichosis

ongoing epidemic in brazil -> causes subcutaneous mycoses in cats -> can transmit to humans (zoonosis)

28
Q

Q: What are the 2 types of fungi that causes deep/systemic mycoses? Difference?

A

A: primary= able to establish infection in a normal healthy host (rarer)

opportunistic= require compromised host in order to establish infection (always around us waiting to take advantage)

29
Q

Q: Name 2 fungi that cause ‘primary’ deep/systemic mycoses. Opportunistic?

A

A: coccidiodes immitis
histoplasma capsulatum

cryptococcus neoformans (form of meningitis)
candida
30
Q

Q: Where are the rates of deep/systemic mycoses high?

A

A: immunosuppressed patients in hospitals

31
Q

Q: What is Candida a cause of? Colonisation? Species?

A

A: common cause of blood stream infections

20-25% of healthy humans have it

6 species predominate as pathogens:

  1. C. albicans (widespread)
  2. C. krusei
  3. C. glabrata
  4. C. parapsillosis
  5. C. tropicalis
  6. C. auris
32
Q

Q: What is Candida albicans? Where? (3) Can be? (3)

A

A: opportunistic commensal

Pretty much all of us have it in our gastrointestinal and genitourinary tracts and skin -> not harmful in healthy humans

but can be harmful in immunosuppressed people -> C. albicans can colonise and invade host tissues

can be: superficial, mucosal, systemic

33
Q

Q: Where can we get superficial Candida infections? (10) Usually due to? Age? (2) Treatment?

A

A: Mouth, throat, skin, scalp, vagina, fingers, nails, bronchi, lungs or the GI tract

Usually due to impaired epithelial barrier function

occurs in all age groups but most common in the new born and elderly

respond readily to treatment

34
Q

Q: What are mucosal Candida infections? Age? Who’s at risk? Forms? (3) What happens when it becomes systemic?

A

A: symptomatic infections

Occurs in the new born and the elderly

Mucocutaneous candidiasis occurs in three forms in people with HIV:

  • Oropharyngeal
  • Oesophageal
  • Vulvovaginal

might see high mortality rates

35
Q

Q: Where are Systemic Candida Infections not normally seen? Risk factors? (3)

A

A: in normal healthy individuals

Main Risk Factors:

  • Chemotherapy
  • Gut-related surgery
  • Catheters (candida can form biofilm)
36
Q

Q: What is Invasive aspergillosis (IA)? Where? (2). Name 2 risk factors.

A

A: emerged as the major clinical problem of common mycology

-common in transplant related settings- CF patients= commonly colonised as lung function is impaired

  1. stem cell transplant
  2. lymphatic leukaemia
37
Q

Q: What’s the difficulty in diagnosing systemic fungal infections? 4 stages of diagnosing?

A

A: few signs and symptoms in patients that are specific for systemic fungal infection

  1. sample acquisition
  2. microscopy (gold standard)
  3. culture = grow fungus on plate
  4. identification
38
Q

Q: Where can sample acquisition be from? (7)

A

A: -Skin

  • Sputum
  • Bronchoalveolar Lavage (good for pulmonary infection eg IA)
  • Blood (systemic)
  • Vaginal swab/smear
  • Spinal fluid (meningitis)
  • Tissue biopsy
39
Q

Q: What are the benefits of microscopy in diagnosis? (2) Requirement?

A

A: cheap and fast

Need to have a well established fungal infection to be able to see it down the microscope

40
Q

Q: What are the downsides to a ‘culture’ in terms of diagnosis? (3) When does it occur? allows?

A

A: slow and prone to contamination and can be difficult to understand

Once it has been identified under the microscope, it can be cultured -> allows susceptibility testing

41
Q

Q: What are non-culture methods of diagnosis? (3)

A

A: Antibody and Antigen-based assays can be used to detect fungal polysaccharides:

  • Glucan
  • Mannan
  • Endolase
  • Proteinase

Crytoccocosis diagnostics= lateral flow assay-> means no lumbar puncture needed for fungal meningitis

PCR (DNA)

42
Q

Q: What are the targets of antifungal treatment? (3) Explain each.

A

A: cell membrane
-fungi use ergosterol instead of cholesterol

DNA synthesis
-some compounds may be selectively activated by fungi, arresting DNA synthesis

cell wall
-unlike mammalian cells, fungi have a cell wall

43
Q

Q: What are the 2 main classes of Cell Membrane Active Antifungals? 3 examples. Method?

A

A: -polyene antibiotics eg Amphotericin B = common but toxic since we’re similar to fungi
-azole antifungals eg itraconazole and flucaonazole= Azole is the main drug group

Main attack against the cell membrane is to INHIBIT THE SYNTHESIS OF ERGOSTEROL = Ergosterol is the main sterol in the fungal membrane

44
Q

Q: What is the main class of Fungal DNA/RNA Synthesis Inhibitors?

A

A: Pyrimidine analogues are commonly used for this
-eg Flucytosine = not great as fungus evolves resistance to it rapidly

-> often combined with azoles

eg fluconazole + flucytosine for Cryptococcal meningitis = combination therapy

45
Q

Q: What is the main class of Cell Wall Active Antifungals? example? Downside? Main components of fungal cell wall?

A

A: echinocandins- caspofungin = works by the non-specific inhibition of b 1, 3 glucan synthase

expensive

MAJOR COMPONENTS: Glucans and Chitin

46
Q

Q: How is the uses of antifungal drugs in agriculture leading to increases in drug resistant infections in humans? Example.

A

A: strains become resistant and then go on to infect immunosuppressed patients

Aspergillus fumigatus is common in environment but can opportunistically infect immunosuppressed patients (CF/transplant)

frontline treatment is triazole which is also used as antifungals on crops -> mutations -> resistant strains

MCD Microbiology (12 decks)

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