Mycology and Parasitology Flashcards by Izzie Setford

What is the most common fungal infection in children?

Fungal scalp infections

- tinea capitis

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Where on the body do the following fungal infections present?

Tinea corporis - trunk, legs or arms
Tinea barbae - face (in males)
Tinea pedis - feet

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How is a dermatophyte infection confirmed?

Microscopy
- interpretation of slides requires experience 
- can't identify the species 
- uses KOH reagent
- simple and rapid results (3-24 hours)
Molecular detection 
- sensitive
- very expensive
Culture
- permits species identification (7-10 days)

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What are the two most common fungal infections in Scotland?

Trichophyton rubrum

Trichophton interdigitale

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List the most common travel associated dermatophyte infections.

Trichophyton tonsurans
- USA, Western Europe, Africa
Trichophton violaceum
- Africa, India

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List the most common occupation related dermatophyte infections.

Trichophyton verrucosum
- farmer, vet
Microsporum gypseum
- gardener

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List the most common pet associated dermatophyte infections.

Microsporum canis
- dogs, cats
Trichophyton mentagrophytens var mentagrophytes
- rodents

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How are dermatophyte infections treated?

Terbinafine 
- 12 weeks for toenails
- risk of SJS
Itraconazole 
- pulse therapy 
Griseofulvin
- scalp
- licensed for children 
Tea tree oil
Garlic

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Name some non-dermatophyte moulds.

Aspergillus 
Rhizopus (strawberry fluff fungus)
Absidia 
Fusarium
Scedosporium
Penicillium marneffei

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How does aspergiullus infection a person?

Found in the soil, plants and the air

- infection by inhalation

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Which aspergillus species are the cause of most aspergillus infections?

A.Fumigatus

A.Falvus

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What are the more serious effects of an aspergillus infection (immunocompromised patients)?

Angioinvasion

haemorrhaging
facial swelling
cough
endocarditis

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What are the clinical manifestations of an aspergillus infection in the immunocompromised?

Lung nodules, sinuses and dissemination to other organs and the CNS
Fever, failure to respond to broad spectrum antibiotics and low grade chest pain

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What are the clinical manifestations of an aspergillus infection in the immunocompetent?

Allergic sinusitis

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Give some examples of mucoraceous moulds.

Rhizopus and Absidia

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How are non-dermatophyte moulds treated?

Amphotericin B (ambisome)
- binds to ergosterol to impair the cell wall function
Itraconazole, voriconazole, posaconazole
- inhibits the fungal-mediated synthesis of ergosterol via cytochrome P450 inhibition (resistance is common)
Caspofungin
- inhibits beta(1,3)-D-Glucan synthase thereby disrupting cell wall synthesis

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List some causes of pathogenic yeast infections.

Candida
Cryptococcus
Malassezia
Rhodotorula 
Saccharomyces
Trichosporon

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Where does yeast live normally in a healthy person?

Normal flora of the skin, mouth, GI tract and vagina

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What species group is the most common type of yeast infection, and name the most common species within it.

Candida

parapsilosis
guilliermondii
albicans

Who is classed as a ‘high risk’ for invasive candida infections?

Immunosuppressed 
Low birth weight babies
Intensive care patients
Trauma 
Extensive antibiotics
Steroids
Drug abuse
Catheter insertion

Which organs does an invasive candida infection affect?

Kidneys (80%), heart (prosthetic valves), GI tract, lungs, liver, spleen, eyes and CNS

Which yeast infections are life threatening even if you have a competent immune system?

Cryptococcus infections

neoformans var neoformans
neoformans var gattii

What are the clinical signs of an invasive crytopococcus infection?

Meningitis 
Productive cough
Chest pain
Weight loss
Fever

In which ways can a lab identify yeast infections?

Culturing 
Chromogenic agar
Auxacolour 2
- 24 hours for results
Maldi Tof

Name some of the topical treatments used for a yeast infection.

Fluconazole, itraconazole, nystatin and clotrimazole

Name some IV treatments for invasive yeast infections.

Amphotericin B (ambisome) - binds to ergosterol to impair cell wall function Fluconazole Caspofungin - inhibits cell wall synthesis Flucytosine - alters protein and DNA synthesis

Define and name some protozoa.

Motile unicellular eukaryotic oragnisms - sporozoa - amoeba - ciliate - flagellate

Name some Helminths.

Trematodes Cestodes Nematodes

What are the four main types of malaria (and where are they most commonly found)?

P.Falciparum - most common - Africa, East Asia, South American and India P.Vivax - SE Asia, India, Central America, North Africa P.Ovale - West Africa P.Malariae - Africa

Name the new emerging species of malaria causing organism.

Plasmodium Knowlesi | - Borneo, Malaysia, Thailand, Cambodia, Vietnam, Singapore and the Philippines

What are the symptoms of Malaria?

``` Fever - irregular (falciparum) - every 2 days (vivax and ovale) - every 3 days (malariae) Headache Chills Vomiting Muscle pain Diarrhoea Respiratory distress Coughing Cerebral malaria (falciparum) ```

What is the minimum time between bite and infection for a malaria infection?

8 days

Briefly describe the malaria parasite travelling from the bite site until causing clinical signs.

The bite allows the parasite to enter the bloodstream It travels to the liver where it resides for several days Then it infects blood cells and causes fever

What laboratory tests can identify malaria?

``` Blood films Antigen testing - detects hrp2 antigen (falciparum) - detects parasite LDH Molecular detection ```

What are the treatment options for malaria?

Malarone - atovaquone/proguanil Deoxycline Choloquine/proguanil Mefloquine (gives vivd dreams)

What are the 5 Schistosomes that can infect humans to cause Schistosomiasis?

S.Mansoni (Africa, Arabia, Egypt, South America) S.Haematobium (Africa, Mediterranean) S.Japonium (Far East) S.Intercalatum (Central and West Africa)

Briefly describe the life cycle of a schistosome.

Cercariae penetrates the skin, losing its tail and becoming a schistosomulae This circulates the body until it reaches the portal circulation and matures into an adult Once in the liver, the do one of two things - liver there for up to 20 years - move to the mesenteric venules of bowel/rectum and lay eggs to ciculate to the liver or be shed in stools

What are the initial symptoms of Schistosomiasis?

Asymptomatic - often Rash develops within 24 hours - swimmer's itch Blood in stool and urine a few months after the infection

What are the late phase symptoms of a Schistosomiasis infection?

Urinary - ulceration of the bladder, blood in urine, calcification of bladder, resulting kidney failure and bladder cancer Intestinal - inflammation of large bowel and rectum and diarrhoea Hepatic - sudden, massive internal bleeding that is often fatal Genital - ulcerative lesion of vagina, vulva, cervix and ovary Neurological - eggs lodge in CNS/brain causing epilepsy and paralysis

Which lab tests can identify a Schistosome?

Serology - detect egg antigens | Microscopy - screening of stools and urine

What is the treatment for Schistosomiasis?

Praqiquantel - paralyses the worm - cant be used as prophylaxis as it has no effect on worms or eggs Effective for all the species

How are the toxoplasma gondii oocysts shed?

In cat stools

What are the intermediate hosts for toxoplasma gondii, and how do they become infected?

Birds, rodents, cattle | - become infected after ingesting contaminated soil and water

Briefly describe the life cycle of toxoplasma gondii oocysts in the human?

Oocysts transform into tachyzoites - these are called bradyzoite cysts in neural and muscle tissue - they can form in skeletal muscle, heart, brain and eyes

How do humans become infected with toxoplasma gondii?

Eating undercooked meat of animals harbouring tissue cysts Consuming food or water contaminated with cat stools Blood transfusion or organ transplantation Transplacentally from the mother to foetus

How is toxoplasma gondii identified in a lab?

Serology - IgG and IgM detection Diagnosis of congenital infections can be done by detecting T.gondii DNA in amniotic fluid - uses PCR

How is toxoplasmosis treated?

Pyrimethamine