Fungal Pathogens

Question 1

what size is fungi?

Answer 1

it is a eukaryotic organism that can be single celled to macroscopic

Question 2

what is in the cell wall?

Answer 2

glucan-chitin cell wall

Question 3

what are the two main forms of growth?

Answer 3

hyphal or yeast

Question 4

what do saprophytes?

Answer 4

decay organic matter

Question 5

what types of infection can you get?

Answer 5

superficial infection, subcutaneous infection or a systemic infection

Question 6

what does superficial infection affect?

Answer 6

skin, nails and hair and the mucocutaneous tissue e.g deramtophytes, candida or malessezia

Question 7

what does systemic infection affect?

Answer 7

deep-seated organs such as candida or aspergillus

Question 8

what are dermatophytes?

Answer 8

they are a group of slow growing organisms that are seen as a cause of disease in the skin, hair and nails - they origante from soil (geophilic), animals (zoophilic) or other humans (anthropophilic)

Question 9

which is more common oncychomycosis or athletes foot?

Answer 9

athletes foot - in adults and sportsmen

Question 10

what is tinea capitis?

Answer 10

scalp ringworm - more common in pre-pubertal children with a global prevalence of around 200 million. It can range from slight inflammation and scaly patches to black dots and grey patches with alopecia in severes.

Question 11

what is tinea pedis, what are the complications and what are the most common causes?

Answer 11

it is uni or bilateral itching, flaking and fissuring of the skin. The soles of the foot (plantar) are dry and scaly. If it affects the whole foot it is Moccasin foot. It may increase sweating (hyperhidrosis) which may make it more severe and can spread to the toes. It may have a secondary bacterial infection. The typical cause is trichophyton rubrum.

Question 12

what else does trichophyton rubrum cause?

Answer 12

onchoymycosis - tinea unguium - thickening, discolouring and dystrophy 0 four main types depending on where it occurs. It can be proximal, distal subungal/lateral, superficial white or total nail dystrophy. T. Interdigitale can also cause this.

Question 13

what is tinea cruris?

Answer 13

it is the itching and scaling, and erythematous plaques with distinct edges. Satellite lesions are sometimes present and it may extend to buttocks, back and lower abdomen. It is more prevalent in men than in women and the typical cause is T. rubrum. The edge includes the active fungi.

Question 14

in tinea capitis what is a kerion celsi?

Answer 14

boddy, inflamed lesion usually from zoophilic dermatophytes that is a sign of scarring and hair loss

Question 15

why are there different reactions in tinea capitis?

Answer 15

it depends on the cause - if it is anthropophilic then it will be adapted to live in host and therefore will not cause as severe an immune response

Question 16

what is favus?

Answer 16

it is the presence of cup shaped crusts or scutula from T. Shoenleinii

Question 17

what is tinea corporis?

Answer 17

it is circular, single or multiple erythematous plaques that may extend from the scalp or groin. the typical casues are anthropophilic or zoophilic dermatopyhytes and can have invasion of follices

Question 18

what is the diagnosis and treatment for dermatophytes?

Answer 18

diagnosis relies on investigations such as culture and microscopy and can use nail or hair trimmings. To treat there are topical antifungals such as clotrimazole or terbinafine for moderate cases and there are systemic oral antifungals for severe disease such as terbinafine, itracanzole and griseofulvin. You must treat all cases of tinea capitis with oral antifungals.

Question 19

what is malassezia?

Answer 19

it is a genus of yeasts that is normal n all humans in their flora just after birth that is most common on the head and trunk. It can cause disease.

Question 20

what is ptyriasis versicolor?

Answer 20

it can be caused by malassezia. It is hyper or hypopigmented lesions that occur on the upper trunk between puberty and middle age. It can reoccur and is more common in the tropics.

Question 21

how would you diagnose ptyriasis versicolor?

Answer 21

you would use microscopy. Culture is difficult and not interpretable. There are round yeast cells and hyphal segments and dimorphic fungi

Question 22

what are candida?

Answer 22

they are a large genus of yeasts that are stained with calcofluor. They will colonise (characteristically depending on species) the GIT and oral muscosal surfaces of healthy people and once in the circulatory system can cause systemic disease as can infect almost any organ. The usually cause topical infections such as thrush or can cause skin disease or keratitis in cornea.

Question 23

what are the four kinds of superficial oral mucosal candida infection and describe them?

Answer 23

acute pseudo-membranous: younger patients, those using an inhaler and have a low CD4 count
chronic atrophic: older patients and erythema
angular cheilitis
chronic hypoplastic: oral leukoplakia
all lesions have potential to undergo malignant transformation

Question 24

what are risk factors for oral mucosal candidosis?

Answer 24

low T cell count, head and neck cancer therapy, general debilitation and use of antibiotics

Question 25

what is candida vaginitis?

Answer 25

it is inflammation of the epithelium that may extend to the labia majora - it results in pruritus, burning sensation +/- discharge and affects 70-80% of women in their child bearing years

Question 26

what is fluconazole?

Answer 26

it is an azole that is highly effective for the superficial candida vaginosis infection - DO NOT use in pregnancy as increases teratologies - use topical

Question 27

where is candida oesophagitis common?

Answer 27

it is common in those with HIV and present in around 10-20% of those with oropharyngeal disease - sample white plaques

Question 28

what is the response to candidaemia?

Answer 28

start antifungals, remove lines where possible and check eyes (occular candidosis) and heart

Question 29

what is candida endocarditis?

Answer 29

it is a rare complication of candidaemia where there are vegetations on the heart valves. it is seen with IV drug users and post valve surgery- fever, weight loss, fatigue, heart murmur and systemic symptoms

Question 30

how do we treat candida?

Answer 30

it depends on strain - severity, oral agent need and sensitivity - echinocandins, azoles, liposomal amphotericin B

Question 31

how may low neutrophil levels trigger hepatospleno candidosis?

Answer 31

it is a disseminated form of candidosis, where abscesses form in the liver and spleen with the classic bulls eye sign. during chemo when there is neutropenia candidaemia may not be detected and when the neutrophils start to regenerate the yeast may lodge in the organs and form abcesses, fever and liver function disturbance.

Question 32

what is aspergillus?

Answer 32

it is a genus of moulds with filamentous fungi. They produce airborne spores spread by inhalation. On a microscopic morpholgy you can see colonies in dish. The most common type is aspergillus fumigatus.

Question 33

what is aspergillosis?

Answer 33

the reaction to inhaling aspergillus in the space occupying the lung cavity

Question 34

what types of reaction are there to aspergillus?

Answer 34

invasive: in the immunocompromised - invasive aspergillus sinitus
chronic: chronic lung disease
allergic: asthma, CF,

Question 35

what is aspergilloma?

Answer 35

solid balls of fungus in cavities from previous TB, surgery or sarcoid

Question 36

what will you see on a chest CT of chronic aspergillosis and invasive?

Answer 36

the patient will present with cough, chest pain, breathlessness and wheezing and on CT you will see cavitation and consolidation
halo and air crescent - grey fuzziness for invasive