Eukaryotic Microbes: Fungal and Parasitic Infections Flashcards Preview

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Flashcards in Eukaryotic Microbes: Fungal and Parasitic Infections Deck (29):

Mycosis means?

- fungal disease
- or mycoses


What are primary fungal infectious agents?

- virulence factors that enable invasion and grow in healthy host


What are opportunistic fungal infectious agents?

- those with low virulence, cause of infection in a comprimised host occurs ( ex HIV, cancer, steroid therapy, pregnancy and diabetes)


How are fungal pathogens grouped?

- via their virulence and severity of disease:
1. Superficial
2. Cutaneous
3. Subcutaneous


Pathogenesis of Mycoses:
- what is the infectious agent?

- spores, hyphal elements and yeasts


Describe the pathogenesis of mycoses !

- the infectious agent enters the body via respiratory, mucous and cutaneous routes (primary pathogens tend to enter via respiratory route)
- most mycoses are not communicable


Pathogenesis of Mycosis:
- Dermatophytes and Candida sp. are linked to humans how?

- they are part of the normal human flora
- most mycoses are not communicable BUT these two are exceptions since they are transmissible


fungal diseases (mycoses) are often?

- superficial eg athletes foot (Trichophyton), dandruff (Malassezia)
- opportunistic (secondary), e.g. thrush (Candida), cryptococcsis (Cryptococcus)
- BUT serious primary mycoses exist (eg. Coccidiodes) and boundaries are blurred (eg. Cryptococcus gattii)


What is the most common fungal infection?

- Candidiasis ( Candida albicans or related sp.)
- commensal on skin/body tracts
- disseminating infection involves a dimorphic switch - Yeast to hypgal


Medically important fungi:
- List some primary pathogens

- Histoplasma capsulatum
- Blastomyces dermatitidis
- Coccidioides immitis
- Paracoccidioides brasiliensis


Medically important fungi:
- List pathogens with intermediate virulence

- Dermatophytes


Medically important fungi:
- List opportunistic pathogens

- Cryptococcus neoformans
- Candida albicans
- Aspergoilus species
- Pneumocycstis carinii
- Mucormycetes


Protist Pathogens:
- Euglenozoa phylum

- Euglenozoa - crystalline rod in flagellum
- Kinetoplastids - mass DNA in single mitochondrion


Fungi as infectious agents:
- molds and yeasts are widely distributed in?
- Are humans are relatively resistant ?
- Are many fungi nopathogenic?
-How many species have been linked to disease in animals ? (vs plants)

- the air, dust and normal flora
- yes
- yes
- 600
- there are more fungal plant pathogens


Protist Pathogens:
- Euglenozoa phylum
L> Trypanosomiasis?

- parasite transmitted by invertebrate vector:
L> Tsetse fly (Glossina sp.) for T. rhodesiense/gambiense
- Assassin/kissing bug (Reduviidae) for T. cruzi


Protist Pathogens:
- Euglenozoa phylum
L> T. rhodesiense, T. gambiense are carried by what insect vector? What disease do they cause?

- Tsetse fly -> Extracellular growth in bloodstream
- African Sleeping Sickness
- T. rhodesiense: A bite by the tsetse fly is often painful and can develop into a red sore, also called a chancre. Fever, severe headaches, irritability, extreme fatigue, swollen lymph nodes, and aching muscles and joints are common symptoms of sleeping sickness. Some people develop a skin rash. Progressive confusion, personality changes, and other neurologic problems occur after infection has invaded the central nervous system. If left untreated, infection becomes worse and death will occur within months.Symptoms usually within 1 to 3 weeks after an infective bite.
- T. gambiense: Occasionally, within 1 to 3 weeks, the infective bite develops into a red sore, also called a chancre. Several weeks to months later, other symptoms of sleeping sickness occur. These include fever, rash, swelling of the face and hands, headaches, fatigue, aching muscles and joints, itching skin, and swollen lymph nodes. Weight loss occurs as the illness progresses. Progressive confusion, personality changes, daytime sleepiness with nighttime sleep disturbances, and other neurologic problems occur after the infection has invaded the central nervous system. These symptoms become worse as the illness progresses. If left untreated, death will eventually occur after several years of infection.


Protist Pathogens:
- Euglenozoa phylum
L> T. cruzi
L> What disease does this cause? What insect vector carries it?

- Chagas' disease
- Reduviid bug -> intracellular growth
- is an inflammatory, infectious disease caused by a parasite found in the feces of the triatomine (reduviid) bug


Protist Pathogens:
- Amoebozoa:
L>How do they achieve movement ?
L> Examples of human pathogens?

- Move via extension of lobe like pseudopods
- Entamoeba histolytica and Acanthamoeba castellani


Protist Pathogens:
- Amoebozoa:
L> Entamoeba histolytica causes what in humans?
L> Where does it hatch?

- causes amoebic dysentery aka bloody diarrhoea
- cysts hatch in the intestine
- They penetrate the gut wall, causing amoebic dysentery


Protist Pathogens:
- Amoebozoa:
L> Acanthamoeba spp.
- briefly describe it
-what does it cause in humans?
- most common presentation is what?

-free living amoebae that also produce cysts
- cause serious infection in immunocompromised hosts
- most common presentation is Amoebic keratitis- a rare disease that involves the amoebae invading the host's cornea of the eye. It can results in permanent visual impairment or even blindness.


Protist Pathogens:
- Diplomonads and Parabasalids
L> both are?
L>explain them. Give an example of each.

- both are amitochondriate (lack a mitochondria)
- Diplomonads: two nuclei and mitosomes
- Parabasalids: parabasal body and hydrogenosomes
- Ex of D: Giardia intestinalis .....P: Trichomonas vaginalis


Protist Pathogens:
- Diplomonads
L> Giardia intestinalis
- What is the usual form of transmission ?
- Symptoms? Treatment?

-faecal-oral via contaminated water
- Due to the formation of resistant CYSTS, symptoms (explosive Diarrhoea etc) can be acute, chronic or asymptomatic carriage
- Treatment = metronidazole


Protist Pathogens:
- Parabasalids
L> Trichomonas vaginalis
- How is it transmitted?
- What is the percentages for males and females that are infected?
- Treatment ?

- It is sexually transmitted (NB- no cysts), causes inflammation and discharge
- 25-50% of women are infected. Men are carriers (generally asymptomatically)
- Treatment = metronidazole


Protist Pathogens:
- Diplomonads and Parabasalids
L> Treatment for both Giardia intestinalis and Trichomonas vaginalis is metronidazole. Describe this treatment.

- anaerobic protists with degenerative mitochondria
- The hydrogenosome/mitosome produces ferredoxin: pyruvate
- Fd:pyruvate reduces metronidazole to release free radicals


Protist Pathogens:
- Alveolates
L> Describe them. Give two examples.

- include dinoflagellate red tides and ciliate parasites but the big problem are the apicomplexans ..
- Apicomplexans are ALL obligate parasites
- Ex= Malaria and Toxoplasma


Protist Pathogens:
- Alveolates
L> Malaria
L> What causes this? What is the parasite(s) vector?

- Plasmodium species ( Vivax and falciparum, primarily)
- transmitted by Anopheles mosquitoes
- they have complex life cycles with liver stage, blood stage, vector stage and plenty more - see text


Protist Pathogens:
- Alveolates
L> Toxoplasmosis
- What causes this?
- Symptoms?
- Are humans the final host?

- Toxoplasma gondii
- usually asymptomatic but transmission to foetus is very serious


Protist Pathogens:
- Alveolates
L> Toxoplasmosis
- What happens in rodents?

- infected rodents lose feat of cat scent but not fear of other aversive stimuli such as open spaces


Protist Pathogens:
- Alveolates
L> Toxoplasmosis
- Humans..not rodents, eh? Does it matter?

- humans are an (inadvertent) intermediate host
- the parasite thinks it is inside a rodent
- higher incidence of mental illness in infected humans
- higher incidence of infection in drivers who crash