Antifungals

Question 1

Antifungals Introduction

Answer 1

Fungi rule own kingdom

Most pathogenic fungi (only a minority) are opportunistic- require a compromised host or disrupted barrier to cause infection

Microscopic fungi exist in two forms
Yeasts
Molds

Yeasts
Unicellular- reproduce by budding
Have a moist shiny appearance when left to grow in colonies

Molds
Multicellular- consist of many branching hyphae
Can reproduce either by translocation of existing hyphae to a new area or through spore formation and spread
Have familiar fuzzy appearance (Rhizopus seen on bread)

Dimorphic fungi can exist in either form
Often mold like at room temperature
Yeast like at body temperature
Referred to as endemic fungi because cause infections endemic to certain regions of the world
Valley fever- Coccidioides immitis causes infection in SW USA and central California

Yeasts (especially Candida) leading cause of nosocomial bloodstream infections
Invasive Candida hard to diagnose- presence in a culture might be colonization not infection; deep seated infections frequently not detected by standard methods and only found on autopsy

Molds generally cause invasive disease in immunocompromised hosts (mild to severe immunosuppression)

Dimorphic usually cause mild self limited disease
Some can cause fatal disseminated disease (particularly in suppressed immunity)

Fungal pathogens can be more difficult to isolate on culture than bacterial organisms; prompt initiation of empiric therapy important when invasive fungal infections suspected
Prophylaxis may be used in highly susceptible populations

Most centers do not conduct antifungal susceptibility testing
Capabilities of host significantly affect successful result
Neutropenic patients with mycoses- neutrophil recovery is significant predictor of success
Patients with prolonged immunocompromised status have much worse prognosis (may need to remove a central venous catheter or or decrease doses of immunosuppressants)

Less antifungal drugs available compared to bacteria
Selective toxicity more difficult to achieve with eukaryotic fungi than prokaryotic

Question 2

Common Yeasts

Answer 2

Candida

Cryptococcus

Question 3

Dimorphic Fungi

Answer 3

Histoplasma
Blastomyces
Coccidioides
Paracoccidioides

Question 4

Molds

Answer 4

Aspergillus
Fusarium
Scedosporium
Mucorales