fungi

• overview

  • fungi
  • yeast
  • candida spp
  • cryptococcus spp
  • mold
  • aspergillus spp
  • mucorales spp
  • dimorphic fungi
  • coccidioides spp
  • pneumocystis spp
  • cutaneous fungi
• yeasts

  • candida spp
  • cryptococcus spp
• candida spp

  • oval budding yeast
  • ubiquitous in environment and colonizes skin, GI, and female genital tract
  • opportunistic pathogen
  • important candida species
  • C. albicans (most common)
  • C. glabrata
  • C. tropicalis
  • C. parapsilosis
  • C. krusei, etc.
• candida infections

  • laboratory identification via culture
  • thrush
  • female (genital) yeast infections
  • white discharge (like cottage cheese), itching, irritation --> not a STD
  • bacteremia
  • hospitalized pts
  • prolonged broad-spectrum antibiotics
  • long-term intravascular catheter in place
• cryptococcus neoformans

  • encapsulated spherical budding yeast
  • soil - esp when contaminated w/ bird excrements
  • transmission: inhalation --> lungs --> CNS
  • laboratory diagnosis:
  • serology test for polysaccharide antigen
  • most commonly associated w/ meningitis in immunocompromised pts (usually HIV+)
• dimorphic fungi

  • exist in a mold form in nature or in lab at 25-30C, and in a yeast/spherule form in tissues or when grown on enriched medium in the lab at 37C
  • endemic pathogens --> their natural habitat is delimited to specific geographic regions
  • acquired by inhalation of spores
  • infect healthy and immunocompromised
• dimorphic fungi

  • histoplasma capsulatum
  • blastomyces dermatitidis
  • coccidioides immitis
• biology of coccidioidomycosis

  • caused by coccidioides immitis
  • ubiquitous in soil
  • cause "valley fever"
• coccidioidomycosis

  • diagnosis: serology
  • 60 % are asymptomatic
  • symptomatic pts
  • usually present 1-3 wks after exposure w/ fatigue, cough, dyspnea, headache, night sweats, myalgias, and sometimes rash
  • primary pulmonary disease
  • mostly self-limiting
  • progresses to chronic pulmonary disease in 5-10%
  • progresses to disseminated disease in 1%
• common opportunistic molds

  • aspergillus spp
  • mucorales spp
• aspergillus spp

  • ubiquitous in air, soil, and decaying matter
  • colonizes respiratory tract
  • branched septate hyphae that produce conidial heads
  • A fumigatus, A. flavus, A. niger, A. terreus
  • transmission: inhalation
  • pulmonary infections
  • risk factors: immunosuppression d/t disease or drugs (neutropenia, BMT/organ transplant, corticosteroids, etc)
  • lab diagnosis
  • culture
  • Aspergillus galatomannan antigen
• mucorales spp

  • ubiquitous in soil and decaying vegetation
  • broad, irregularly branched, twisted, and aseptate hyphae
  • rhizopus spp
  • mucor spp
  • rare but high mortality --> generally only infect severely immunocompromised
  • pulmonary infection, sinus infections (can erode into brain)
  • prophylaxis in severely immunocompromised (usually BMT) pts --> posaconazole or isovuconazole
• pneumocystis jirovecii

  • colonize respiratory tract --> opportunistic pathogens
  • used to be classified as a protozoan, now Ascomycetes fungus
  • lab diagnosis: microscopy w/ staining, do not grow on culture
  • largely associated w/ pulmonary disease
  • risk factors
  • HIV
  • immunosuppression
  • cancer/malignancy
  • treatment or prophylaxis --> SMX/TMP
• cutaneous fungi - dermatophytes

  • invade the skin, hair, or nails --> able to break down the keratin surfaces of these structures
  • onychomycosis (toe nail) --> oral terbinafine
  • tinea infections --> usually treated w/ topical antifungals, OTC, or Rx