What kind of organisms are fungi?
What do fungi comprise?
- Higher fungi
What kind of organisms are yeasts?
What are moulds?
What are higher fungi?
Mushrooms and toadstools
What survival advantage do fungi have?
They can survive in an environment where nutrients are limited
What are saprophytes?
Organisms that live off dead organic matter in soil and water.
Many fungi are saprophytes
What are the main forms of fungal growth?
- Yeast like growth via simple budding
- Mould-type growth
What does yeast like growth allow for?
Growth in the simplest form
What can some yeast form?
How do yeasts that form pseudohyphae grow?
Buds elongate to form filaments
What happens in mould-type growth?
Numerous microscopic, branching, filamentous hyphae are produced to form extensive arrangement of mycelia
What is the purpose of mycelia?
They are used to gain nutrients and reproduce
What do reproductive mycelia do?
How do reproductive mycelia produce spores?
Either sexually or asexually
What do the spores produced by mycelia do?
Disseminate throughout the atmosphere and colonise new environments
What do mycelia look like?
What is meant by dimorphic growth?
It will invade a tissue in its yeast form, yet form a mould in the living environment
Fungi can, and commonly do, grow in this manner
What is the exception to the dimorphic growth of fungi?
How does Candida spp. grow?
It stays in its yeast form except for producing pseudohyphae
On what basis can fungi be classified?
- Degree of tissue involvement
- Mode of entry into the host organisms
What are the classifications of fungi?
What is meant by superficial fungi?
Localised to hair, skin, and nails
How common are subcutaneous fungi?
What is meant by systemic fungi?
Deep infections of internal organs
When are opportunistic fungal infections seen?
Only in immunocompromised individuals
Give 5 examples of fungi that can be superficial
Give 4 examples of fungi that can be systemic
Give 4 examples of fungi that can be opportunistic
How common are fungal infections in the UK?
Most fungal infections are uncommon to healthy individuals, except for candiasis or dermatophyte infections, which are quite common
What are dermatophytes?
Superficial fungi that grow on keratin
Where are dermatophytes mainly seen?
On skin or hair
How can infection from dermatophytes be acquired?
From people, animals, or the environment, depending on the species
What are the main species implicated in dermatophyte infection?
How do dermatophyte infections commonly present?
What is ringworm?
Red scaly patches that spread out that are itchy, but rarely painful
On what basis are dematophyte infections clinically labelled?
By their sites of infection
What are the clinical labels of dermatophyte infection?
- Tinea Capitis
- Tinea Corporis
- Tinea Pedis
Where does Tinea Capitis affect?
Head and neck
Where does Tinea Corporis affect?
What is Tinea Pedis?
Where are candida species found?
Widely distributed in the environment
What do the candida species form part of?
The normal commensal population in the GI tract, skin, and female genital tract
What is the result of candida species forming part of the normal commesnal population?
Following the use of broad spectrum antibiotics, a fungal growth may develop
Other than antibiotics, how else may a fungal growth develop?
As a result of any immune deficiency
What do yeast fungi contain?
What are most fungal infections caused by?
What does candida cause?
Oral and vaginal thrush
What happens in oral and vaginal thrush?
Creamy, curd-like plaques are produced
What do the plaques in thrush cause?
Pain and itching
Who can develop a systemic infection from Candida spp.?
Individuals who suffer from neutropenia
Why can Candida infection not be diagnosed by growth on laboratory media?
As they are part of the normal commensal flora, the growth on laboratory media can prove inconclusive
How can Candida infection be viewed?
What should any results of Candida infection investigation be determined in relation to?
The clinical picture
Who is at risk of developing opportunistic fungal growth?
- Metabolic defects
- Undergone surgery
What fungi can grow opportunistically?
- Aspergillus spp.
- Pneumocystis jiroveci
When can candiasis develop systemically?
- In severely immunocompromised individuals
- Following chemotherapy
What are aspergillus spp.?
Ubiquitous saprophytic fungi
What can aspiration of aspergillus spores give rise to?
Type III hypersensitivity reaction (Farmers lung)
What can become colonised by aspergillus?
Healed old cavities or bronchiectasis
What is caused when healed cavities or bronchiectasis are colonised by aspergillus?
What can happen in aspergillus infection in neutropenic patients?
They begin in the lung, and can develop into disseminated systemic disease
How can aspergillus infections be diagnosed?
- Antibody detection
How can aspergillus infections be treated?
What is cryptococcus?
A saprophyte that infects humans
Where is cryptococcus commonly found?
In pigeon faeces
What is the main species of the cryptococcus genus?
What is cryptococcus neoformans associated with?
Subacute or chronic form of meningitis
What does meningitis caused by cryptococcus neoformans result from?
Inhalation of the species
In whom does pneumocystis jiroveci cause infection?
Only patients with severe T-cell dysfunction
Why may someone have severe T-cell dysfunction?
- Primary immune deficiencies
- Immunosupressive drugs
What kind of fungus is pneumocystis jiroveci?
How is pneumocystis jiroveci transmitted?
Via the respiratory route
How do patients with pnuemocystis jiroveci present?
- Progressive dyspnoea
- Unproductive, dry cough
What does pneumocystis jiroveci cause?
Pneumocystsis pneumonia (PDP)
What happens in PCP?
- Pulmonary consolidation
- Decreased pO2
How can pneumocystis jiroveci be diagnosed?
What is the result of fungi being eukaryotes?
They share a similar cellular structure to human cells
What is the result of fungi sharing a similar cellular structure to human cells?
Any anti-fungals used have the potential to cause damage to our own cells
What are the main types of anti-fungals commonly used?
What do azoles do?
Block the action of cytochrome C450
What does the type of azole given depend on?
The fungus in question
Give 4 types of azole
What does terbinafine do?
Inhibits squalene epoxidase with resultant accumulation of aberrant and toxic sterols in the cell wall
What do polyenes do?
Forms a pore in the fungal membrane
What do echinocandins do?
Inhibit the synthesis of 1,3-ß-glucan
What is 1,3-ß-glucan?
A molecule in the cell wall of pathogenic fungi
What are protozoan?
Single celled eukaryotes
How do protozoan differ from fungi?
In their cell walls and life cycle
What are the main two protozoan worldwide?
What is the prevalence of toxoplasmosis?
What is the prevalence of malaria?
How can the life cycles of protozoan be classified?
Give two examples of a protozoa with a simple life cycle
Give two examples of protozoa with complex life cycles
Draw a diagram illustrating the simple life cycle of a protozoa
Draw a diagram illustrating the complex life cycle of a protozoa
What is a trophozoite?
The active protozoa which is mitotically dividing constantly
What is the cyst?
The non-replicating, resistant form of the protozoa
What are the eggs in the complex life cycle seen to be?
The infectious form of the protozoa
What are the main groups of protozoa?
What are the simplest forms of protozoa?
What are amoebae characterised by?
A feeding and dividing trophozoite
How can amoebae survive in most environments?
They can form a resistant cyst
What form do flagellates have?
A trophozoite form with a flagella attached
What is the purpose of flagellates flagella?
Give an example of a flagellate
What are apicomplexa?
Protozoa that are intracellular, and have a sexual and asexual reproduction life cycle
Give two apicomplexa
Give 3 types of protozoa that affect humans to cause disease
- Entamoeba histolytica
- Giardia lambia
What does entamoeba histolytica infect?
The large intestine
How are entamoeba histolytica transmitted?
By faeco-oral route
How do entamoeba histolytica infect the large intestine?
They adhere to the intestinal epithelium
What can entamoeba histolytica lead to?
- Brain or liver abscesses
Is giardia lamblia common worldwide?
How is giardia lamblia transmitted?
In the water and food supplies
What allows giadia lamblia to be transmitted in the food and water supplies?
What path do giardia lamblia take in the human body?
They divide in the jejenum, then adhere to the intestinal walls
How do giardia lamblia divide?
By binary fission
How do giardia lamblia adhere to the intestinal wall?
By sucking discs
What do giardia lamblia form that allows their transmission to the environment?
Cysts in faeces
What are the symptoms of giardia lamblia?
- Abdominal pain
- Bulky, fatty stools
Why does giardia lamblia infection cause bulky, fatty stools?
Due to poor fat absorption
What kind of protozoa is cryptosporidium?
How is cryptosporidium transmitted?
By farm animal contact
Who is cryptosporidium infection common in?
Children and immunosuppressed individuals
What are the symptoms of cryptosporidium infection?
Self-limiting watery diarrhoea with abdominal cramps
How does cryptosporidium produce its symptoms?
The protozoa interferes with the sodium pumps in the small intestine
What causes malaria?
Four species of the genus plasmodium;
- P. Falciparum
- P. Vivax
- P. Ovale
- P. Malarie
How many people live under the treat of malaria?
More than 1.5 billion people
How many children under the age of 5 years die in Africa each year from malaria?
How does malaria get into the body?
The oocytes of plasmodium (sporozoa) are injected into the circulation of individuals by the female Anopheles bites
What happens to the malaria parasites once they are inside the body?
They multiply in the hepatocytes in the liver before invading the red blood cells and multiplying
How are the systemic features of malaria caused?
The plasmodium provoke the release of cytokines from the red blood cells
How are plasmodium spread to other cells from RBCs?
They cause the lysis of the erythrocytes and so can spread to other cells, producing very large numbers
What happens to the malaria infected erythrocytes?
They can adhere to the endothelial wall, causing cerebral malaria
How can malaria be transmitted from an infected individual?
The plasmodium protozoa differentiate into the sexual stage and can be taken up by another biting female Anopheles, and develop in the mosquito gut before migrating to the mosquitos salivary glands
Between that do the symptoms of malaria vary?
- Plasmodium species
What are the symptoms of malaria?
- Pre-hepatic jaundice
- Dark pigmented urine
Why is dark pigmented urine a symptom of malaria?
From erythrocyte destruction
What secondary pathologies can malaria cause?
- Cerebral malaria
What is the most fatal malaria species?
What is the most common malaria species?
What is plasmodium Vivax known to do?
Reoccur from latency
What does treatment for malaria involve?
What is the purpose of chemotherapy in malaria treatment?
To destroy the parasites
What is the best means to reduce malaria cases?
How is malaria prevented?
- Use of mosquito nets while sleeping
- Prophylaxis regularly taken
Draw a diagram illustrating the cycle of malaria
What causes toxoplasmosis?
The protozoan toxoplasmosis gondii
Where does toxoplasmosis gondii have its life cycle?
What can toxoplasmosis gondii infect?
All warm blooded mammals
How can humans become infected with toxoplasmosis gondii?
- Through ingestion of the oocytes from cat excrement contaminating food
- Can spread vertically to foetus
What does toxoplasmosis cause in the primary infection?
Who is toxoplasmosis a problem for?
Why is toxoplasmosis a problem for immunocompromised individuals?
Because toxoplasmosis gondii persists inside the host cell for very long periods, yet falling immunity can allow for reactivation
Where can toxoplasmosis spread to?
What is the result of toxoplasmosis spreading to the brain?