mycology

Question 1

types of fungy

Answer 1

 “dermatophytes”
- Trichophyton species eg T.rubrum, T.
mentagrophytes
- Microsporum species eg M.canis
- Epidermophyton species eg. E.floccosum

 Yeasts/dimorphic fungi
- Candida sp, Malassezia spp

 Moulds
- Aspergillus sp, Fusarium sp, Scopulariopsis sp

Question 2

diagnosis

Answer 2

 Skin scrapings
 Nail clippings, sub ungual debris
 Hair – plucked, scrapings
 Microscopy
 Keratin dissolved by KOH (potassium hydroxide)
 Culture
 5-7 days

Question 3

species identification

Answer 3

T.Rubrum - agar

M. Canis - Macroconidia

C. Albicans - arthrospores

Question 4

treatment

Answer 4

 Topical for skin and mucous membranes

• Polyenes (nystatin)
• Azoles (cotrimazole, miconazole) (canestan, daktarin)
• Allylamines (terbinafine) (lamosil)

 Oral for nail and scalp

• Allylamines (terbinafine)
• Triazoles (itraconazole)

 Surgical removal of chronically infected nails

 Antifungal shampoos for scalp ringworm (to
reduce infectivity)

Question 5

subcutaneous infection

Answer 5

 Fungal elements implanted directly into skin
and deeper dermis. Common in the tropics
 Chronic granulomatous infection involving
skin, bone and lymphatics
 Sinuses develop, infection becomes
polymicrobial
 May resolve spontaneously but may require
amputation for cure

Question 6

systemic infection

Answer 6

 UK
 Opportunist infection
- Candida albicans and non-albicans yeasts
- Aspergillus species
- Cryptococcus neoformans
- Pneumocystis jiroveci (carinii)
- Others (mucorales, Scedesporium, Fusarium spp)

 Elsewhere
 As above but also endemic including…………………
- Histoplasma, Coccidioides, Paracoccidioides,
Blastomycoses spp etc

Question 7

candidosis

Answer 7

 risk factors

• prematurity
• neutropenia
• steroids, antibiotics
• Chemotherapy/mucositis
• Abdominal surgery
• long-lines/TPN (IV feeding)
• Colonisation
• Cross infection

Question 8

aspergillus

Answer 8

 Ubiquitous airborne
fungus
 common cause of
infectious death in
many transplant units

Question 9

aspergillus syndromes

Answer 9

 Saprophytic colonisation

• upper airways (17% smokers (especially marijuana))
• Pre-existing ling cavity (eg old TB) (Aspergilloma (fungal ball))

 Allergic
- hypersensitivity

 Toxin mediated
- Alfatoxins

 Invasive aspergillosis

Question 10

risk factors for invasive aspergillosius

Answer 10

 NEUTROPENIA
 other
- Solid organ transplantation
- corticosteroid usage
- GvHD
- Virus infection
- CMV
- influenza

Question 11

invasive aspegillus

Answer 11

 Nonspecific symptoms
 Fever, cough, pleuritic chest pain
predominate
 rhinocerebral disease may develop with
sinusitis, epistaxis, facial pain

Question 12

invasive pulmonary aspergilosis

Answer 12

 Occurs sporadically and in clusters via
inhalation of spores
 high mortality approaches 90% in SCT
 Angioinvasion by branching septate hyphae
 lnfarction of tissues cavitation of lung
 dissemination

Question 13

cryptococcus

Answer 13

Capsulate yeast
 C neoformans is major human pathogen
- Varieties
- C neoformans var. grubii
- C neoformans var. neoformans
- C neoformans var. gattii

Virulence factors
 Capsule
- Prevents phagocytosis
- Immunomodulatory

Environmenal in soil, bark, bird droppings

Mainly associated with T cell defects but C gattii seen
in normocompotent hosts

Question 14

manifestations

Answer 14

Acquired by inhalation
 Pulmonary manifestation usually subclinical
 Meningitis predominates (neurotropism)
- Chronic
- Plus cerebritis
- May be complicated by raised intecranial pressure
 Also cutaneous

Diagnosis
 Culture from blood or CSF
 demonstration of capsular yeasts
- india ink stain
- Antigen test

Question 15

pneumocystis jiroveci (carinii)

Answer 15

 Related to brown rust fungus
 environmental niche unknown
 ? Primary infection or reactivation
 can be nosocomially acquired
 risk of infection related to CD4 count
- HIV disease
- lymphoma and post BMT
- vasculitides (Wegeners) Rh arthritis

Question 16

PCP

Answer 16

 Intense interstitial pneumonitis
 fever and breathlessness
disproportionate to chest X ray
 desaturate on exercise
 diagnosis by demonstration of PC in
BAL or by PCR

Question 17

dianose infection

Answer 17

 Isolation from a sterile site
 blood cultures (not aspergillus)
 fluids (CSF etc)
 tissues
 antigen testing and PCR
 Radiology

Question 18

antifungals

Answer 18

 fungi have eukaryotic cells which have few
differences from human cells
 fungi have relatively few unique and essential
targets for anti-fungal agents
 cell wall - chitin as the main structural polymer
 cell membrane - unique fungal sterols (ergosterol)
 some unique cytoplasmic membrane enzymes

Question 19

available antifungals

Answer 19

 Conventional amphotericin B
 lipid preparations amphotericin
 Fluconazole, itraconazole
 newer agents/combinations
 voriconazole, posaconazole
 Echinocandins (caspofungin, anidulafungin)
 Immunomodulation (GM-CSF, IFN gamma)