Opportunistic fungal infections 1 - Aspergillosis
Opportunistic fungal pathogens cause disease in individuals whose immune system
is weak.
Opportunistic conditions arise due to:
- Primary immunodeficiency- caused by mutations affecting any of the genes
that control the immune response
- Secondary immunodeficiency- a consequence of another disease, secondary
to environmental factors (starvation) or adverse consequences of medical
intervention
Aspergillosis is a disease caused by the ‘Aspergillus fumigatus’ species whose
spores are present in the air.
Inhalation of Aspergillus spores is a common daily occurrence. A healthy immune
system would normally remove the spores and no symptoms or infection would
occur, however in individuals whose immune system may be suppressed either
because of illness or drugs, spores may germinate and resulting tissue or systemic
Aspergillus invasion can result.
- Individuals with allergies can also be vulnerable to allergic aspergillosis
Aspergillus species play a significant role in the degradation of plant material and it is
commonly found in soil, food and air vents. Within hospitals they are found in
showerheads, hospital water storage tanks and potted plants.
Spores are inhaled which then begin to germinate and then become hyphal. Hyphal
elongations and dichotomous branching then occurs leaving a mass of hyphae
(plateau phase).
Immunodeficiency is the
main predisposing factor in
the development of invasive
aspergillosis and can
develop during the
treatment of cancer as
Chemotherapy targets both
cancer and fast-dividing
cells, like neutrophils, which
have an important role in
host defence against
invasive aspergillosis.
Individuals who have pre-
existing lung injury are at risk of developing chronic pulmonary aspergillosis (CPA) or
chronic necrotizing pulmonary aspergillosis (CNPA) because of fungal growth in
damaged tissues or pre-existing cavities.
Opportunistic fungal pathogens cause disease in individuals whose immune system
is weak.
Opportunistic conditions arise due to:
- Primary immunodeficiency- caused by mutations affecting any of the genes
that control the immune response
- Secondary immunodeficiency- a consequence of another disease, secondary
to environmental factors (starvation) or adverse consequences of medical
intervention
Aspergillosis is a disease caused by the ‘Aspergillus fumigatus’ species whose
spores are present in the air.
Inhalation of Aspergillus spores is a common daily occurrence. A healthy immune
system would normally remove the spores and no symptoms or infection would
occur, however in individuals whose immune system may be suppressed either
because of illness or drugs, spores may germinate and resulting tissue or systemic
Aspergillus invasion can result.
- Individuals with allergies can also be vulnerable to allergic aspergillosis
Aspergillus species play a significant role in the degradation of plant material and it is
commonly found in soil, food and air vents. Within hospitals they are found in
showerheads, hospital water storage tanks and potted plants.
Spores are inhaled which then begin to germinate and then become hyphal. Hyphal
elongations and dichotomous branching then occurs leaving a mass of hyphae
(plateau phase).
Immunodeficiency is the
main predisposing factor in
the development of invasive
aspergillosis and can
develop during the
treatment of cancer as
Chemotherapy targets both
cancer and fast-dividing
cells, like neutrophils, which
have an important role in
host defence against
invasive aspergillosis.
Individuals who have pre-
existing lung injury are at risk of developing chronic pulmonary aspergillosis (CPA) or
chronic necrotizing pulmonary aspergillosis (CNPA) because of fungal growth in
damaged tissues or pre-existing cavities.
