This document discusses opportunistic fungal infections, describing the most common fungal pathogens including Candida, Pneumocystis, Cryptococcus, Aspergillus, and Zygomycetes. It outlines the main risk factors for developing fungal infections like neutropenia, AIDS, diabetes, corticosteroid use, and more. For each pathogen, it summarizes the clinical presentations, defense mechanisms, treatment approaches, and prevention strategies. The document emphasizes that opportunistic fungal infections are increasingly difficult to diagnose, treat and prevent, posing an ongoing challenge.

1. OPPORTUNISTIC FUNGAL
INFECTIONS
Smilja Kalenic, MD, PhD
Clinical Hospital Centre
Zagreb, Croatia

2. LEARNING AND PERFORMANCE
OBJECTIVES
• to learn about the most frequent
opportunistic fungi and to
understand main risk factors for
developing infection
• to be able to predict the most
probable agent of invasive fungal
infection in a particular
compromised patient state and to
be able to act preventively

3. FUNGI
• EUCARIOTIC ORGANISMS
• TWO BASIC FORMS:
- YEASTS
- MOLDS

4. MYCOSES
1. SUPERFICIAL
2. CUTANEOUS
3. SUBCUTANEOUS

5. MYCOSES
4. ENDEMIC (PRIMARY,
SYSTEMIC):
Histoplasma capsulatum,
Coccidioides immitis,
Blastomyces dermatitidis,
Paracoccidioides brasiliensis

6. MYCOSES
5. OPPORTUNISTIC
endogenous
- Candida (different
species)
- Pneumocystis carinii (?)

7. MYCOSES
5. OPPORTUNISTIC
exogenous
- Cryptococcus neoformans
- Aspergillus (different
species)
- Zygomycetes
- MANY OTHER FUNGI

8. Candida albicans and
other Candida species
• Harmless inhabitants of
the skin and mucous
membranes of all humans
• Normal immune system
keeps candida on body
surfaces

9. MAIN DEFENSE
MECHANISMS AGAINST
CANDIDA I.
• skin and mucous
membranes integrity
• presence of normal
bacterial flora

10. MAIN DEFENSE
MECHANISMS AGAINST
CANDIDA II.
• phagocytosis
• killing, mostly in
polymorphonuclear cells,
less in macrophages
• T-cells (CD4)

11. THE MOST IMPORTANT
RISK FACTORS
1. Neutropenia
2. Diabetes mellitus
3. AIDS
4. SCID
5. Myeloperoxidase defects
6. Broad-spectrum antibiotics

12. THE MOST IMPORTANT
RISK FACTORS
7. Indwelling catethers
8. Major surgery
9. Organ transplantation
10. Neonates
11. Severity of any illness
12. Intravenous drug addicts

13. CLINICAL FORMS OF
CANDIDIASIS
1. Cutaneous and
mucosal
candidiasis

14. CLINICAL FORMS OF
CANDIDIASIS
2. Invasive (systemic,
disseminated,
hematogenous)
candidiasis

15. INVASIVE CANDIDIASIS
• Usually begins with
candidemia (but in only
about 50% of cases
candidemia can be proven)
• If phagocytic system is
normal, invasive infection
stops here

16. INVASIVE CANDIDIASIS
• If phagocytic system is
compromised, infection
spreads to many organs
and causes focal
infection in these organs
• mortality of candidemia
is 30-40%

17. DIAGNOSIS OF INVASIVE
CANDIDIASIS
• Gram stain and isolation
from blood, CSF or
peritoneal fluid
• isolation and/or pathology
positive of organ involved
• other tests are of lower
significance for the diagnosis

18. EPIDEMIOLOGY
Although candidiasis is
endogenous in most
cases, cross infections
are described, especially
in intensive care unit
patients.

19. Pneumocystis carinii
• Present in lungs of many
mammals, including
humans, in persistent but
harmless infection

20. Pneumocystis carinii
• Main defense mechanism
is T-cell mediated
• causes interstitial
pneumonitis in
compromised patients
• treatment and prevention:
cotrimoxasole or pentamidine

21. Cryptococcus neoformans
• Occurs worldwide in soil and
in bird droppings
• Prominent feature: thick
polysaccharide capsule,
which causes evasion from
phagocytosis

22. MAIN DEFENSE
MECHANISMS AND
PATHOGENESIS
• T-cells responsible for
defense
• Cryptococcus reaches
humans by inhalation of
aerosolized yeast cells

23. CHRONIC MENINGITIS IN
AIDS-PATIENTS
• The most important
clinical syndrome
• treatment: amphotericin
B+/-flucytosine
• recurrence prevention:
fluconazole

24. EPIDEMIOLOGY OF
CRYPTOCOCCOSIS
Infection is always
exogenous, is not
transmitted from human
to human

25. Aspergillus species
• Aspergilli are worldwide
occurring saprophytes,
living in soil and on
plants; they have small
conidia that form
aerosols

26. • Main defense mechanism is
phagocytosis
• Main risk factors are
hematological malignancy,
bone marrow transplantation
and corticosteroid therapy

27. The most frequent syndromes
are: - aspergilloma
- invasive aspergillosis
(high mortality rate)
Treatment: amphotericin B,
itraconazole, flucytosine
and surgery
Prevention: avoid exposure
to conidia (new buildings in the
hospital!)

28. ZYGOMYCETES
• Zygomycetes are ubiquitous
saprophytes
• main host defense is
phagocytosis
• main risk factors are diabetes,
hematological malignancies,
corticosteroid therapy

29. Major clinical syndrome is:
Rhinocerebral mucormycosis
(infection of nasal passages,
sinuses, eyes, cranial bones
and brain)
Treatment: surgery and
amphotericin B
Prognosis: very poor

30. OPPORTUNISTIC FUNGAL
INFECTIONS ARE:
• difficult to diagnose
• difficult to treat
• difficult to prevent
• more and more frequent
• a great challenge for a
future work in all fields