Opportunistic Mycoses

1
Opportunistic Mycoses

• Aspergillosis
• Zygomycosis
• Hyalohyphomycoses
• Phaeohyphomycoses

2
Opportunistic mycoses

• These organisms (moulds, yeast, mushrooms, smuts,
  and rusts) are fungi ubiquitous in the
  environment
• They are responsible for decomposing dead plants
  and animals (mother natures excellent
  recyclers of scarce organic matter). We use
  the term saprophytes.
• Emmons introduced the term saprobe to replace
  the term saprophyte

3
Opportunistic mycoses

• Conidia and spores of these saprobes are commonly
  aerosolized, inhaled, and consumed by humans
• Many of the saprobes are bread moulds
• Even though they are consumed and inhaled in
  large numbers, these fungi have low virulence and
  therefore do not initiate disease in otherwise
  healthy individuals

4
Opportunistic mycoses

• Fungi that live as saprobes and do not affect the
  the human host unless the host has some
  compromising condition, are opportunistic
  pathogens
• Compromising conditions include
• Preexisting illness, especially malignancies,
  immune deficiencies, and diabetes mellitus
• Medications, especially antibiotics and steroids

5
Opportunistic mycoses

• Compromising conditions
• Pregnancy
• Belonging to certain demographic groups
• Neonates
• Elderly
• Ethnics
• Physical laborers
• Etc.

6
Opportunistic mycoses

• Virtually any fungus can cause opportunistic
  infections, depending on the severity of the
  hosts immunocompromised status
• One lab procedure used to assess the likelihood
  that a given isolate is a pathogen or contaminant
  is to determine if it can grow at body
  temperature
• An isolate that cannot grow at body temperature
  is not likely to cause an infection

7
Opportunistic mycoses

• The most common opportunistic fungal infections
  are zygomycosis, aspergillosis, candidiasis, and
  cryptococcosis
• Candida albicans and Cryptococcus neoformans are
  considered to be primary pathogens by some
  clinical mycologists because the predisposing
  condition does not have to be severe
• Other Candida and Cryptococcus species are less
  virulent and therefore bona fide opportunists

8
Opportunistic mycoses

• Candidiasis and cryptococcosis are discussed in
  the Yeast Power Point series
• Saprobes other than Aspergillus and zygomycetes
  are less commonly associated with human
  opportunistic infections
• Saprobic moulds that cause opportunistic mycoses
  characterized by having hyphae in tissue are
  called hyphomycoses

9
Opportunistic mycoses

• If the hyphomycosis is caused by a hyaline mould
  it is referred to as hyalohyphomicosis
• If the hyphomycosis is caused by a dark colored
  mould it is referred to as phaeohyphomicosis
  (phaeo means dark colored)

10
Opportunistic mycoses

• There are hundreds of additional species of fungi
  responsible for opportunistic mycoses
• Most of these fungi are rarely encountered in
  the general hospital patient population
• Many of the fungi that cause the mycoses
  discussed above are encountered as environmental
  contaminants