Opportunistic mycoses

1
Opportunistic mycoses

• Laboratory personnel who process clinical
  specimens and identify fungi grown from them must
  be able to identify the most common ones and help
  the physician decide if it is causing the
  patients problem
• Some of these fungi, along with many of the
  classical pathogens, are included in the mycology
  competency tests

2
Aspergillosis

• Etiology many species of Aspergillus exist but
  only a few species are pathogenic
• The most commonly isolated species is Aspergillus
  fumigatus
• Other relatively common species include
  Aspergillus flavus, Aspergillus terrus and
  Aspergillus niger

3
Aspergillosis

• Etiology
• Identification to the Genus level is not
  difficult
• Species identification is difficult but may not
  be necessary since treatment (anti-fungal
  antibiotics) is the same for most species
• Each isolate can be tested against selected
  drugs in vitro for antimicrobial susceptibility

4
Aspergillosis

• Epidemiology
• Aspergillus is the most common Genus of fungi in
  the environment
• Aspergillus grows world wide in soil rich in
  organic matter
• It is one of the most common bread molds
• Aspergillus are frequently secondary pathogens
• Predisposing conditions include bronchiectasis,
  leukemia, aplastic anemia, carcinoma,
  tuberculosis, immunosuppressive drugs,and
  antimicrobial agents

5
Aspergillosis of pre-formed lung cavity
6
Aspergillosis

• Clinical manifestations
• Allergic bronchopulmonary bronchitis
• Synomym hypersensitivity pneumonitis a type 1
  hypersensitivity
• Associated with allergic response of IgE and
  eosinophils
• Display extrinsic asthma, pulmonary infiltrates,
  eosinophilia

7
Aspergillosis

• Clinical manifestations
• Pulmonary aspergillomas (or fungus balls)
• Fungal hyphae and cellular debris form in
  cavities in the bronchial tree
• Often causes hemoptysis (expectoration of blood
  or blood-stained sputum

8
Aspergillosis

• Clinical manifestations
• Active (acute) invasive bronchopulmonary
  aspergillosis
• Invasion of lung parenchyma - alveoli
• Cause hemorrhage and infarction (necrosis of
  tissue due to obstrucion of upstream arterial
  blood supply
• May lead to disseminated aspergillosis
• Symptoms may mimic acute bacterial pneumonia and
  include fever, cough, pleuritic pain
• The typical patient is granulocytopenic and
  receiving broad-spectrum antibiotics for
  unexplained fever

9
A. fumigatus growing in air sacs of a hen
duringepidemic aspergillosis in poultry
10
Aspergillosis

• Clinical manifestations
• Mycotoxicosis due to ingestion of contaminated
  foods
• A. flavus produces an extremely potent cancer
  causing toxin, aflatoxin
• Suspect foods food crops such as nuts, corn
  wheat that may sit damp in the field or in
  storage
• Recent data suggests the possibility that
  multiple schlerosis may be the result of chronic
  mycotoxicosis