This document summarizes a medical seminar presentation on opportunistic fungal infections caused by Aspergillus, Candida, and Cryptococcus. The presentation covers the causative organisms, morphology and distribution, pathogenesis and clinical features, laboratory diagnosis, epidemiology, and treatment of aspergillosis, candidiasis, and cryptococcosis. It provides details on how these fungi cause infection in immunocompromised individuals and the characteristics and diagnostic methods for each type of fungal infection.

1. MEDICAL MYCOLOGY
SEMINAR
Opportunistic fungal infections – Aspergillosis, Candidiasis,
Cryptococcosis
Amelendhu Vimalkumar

2. Introduction
• It is caused by either,
a. Normal commensal fungi ( Candida albicans)OR
b. b. Fungi found in nature ( Aspergillus fumigatus)
• These type of mycoses occur in immunocompromised/ immunodeficient
individuals ( AIDS patients, individuals with malignancies, individuals
suffering from diabetes mellitus, individuals receiving immunosuppressive
drugs, patients who suffer from debilitating diseases etc.)
• There is suppurative response to the infection.
• It leads to necrosis of the affected tissues.
• Re- infection may occur.

3. 1. Diseases and Causative Organisms
2. Morphology and Distribution
3. Pathogenesis
4. Clinical features
5. Laboratory Diagnosis
6. Epidemiology
7. Treatment

4. Diseases and Causative Organisms
1. Aspergillosis – Aspergillus fumigatus , Aspergillus niger, A. flavus .
2. Candidiasis - Candida albicans , C. krusei, C. glabrata, C. tropicalis
3. Cryptococcosis – Cryptococcus neoformans, C. gattii, C.albidus,
C.laurentii

5. Morphology and Distribution
1 .Aspergillus fumigatus 2 .Candida sp 3 .Cryptococcus neoformans
• Common mould seen on damp
bread or organic matter
• Their habitatis soil and dust
• Highly pathogenic for birds
• The spores are ubiquitous
• World wide distribution
• It is yeast like fungus
• It is an ovoid or spherical
budding cell
• It produces pseudomyceliaboth
in tissues and in culture.
• Candida albicans produce true
hyphae
• Candida glabrata – only yeast
cells
• World wide distribution
• It occurs world wide
• Mainlyin Europe ( European
blastomycosis)
• In India it is the commonest
systemic mycoses
• It produces mastitis in cattle
• Basidiomycetousyeast
• It is a round or ovoid budding
cell.
• It has a prominent
polysaccharidecapsule

6. 2
1
3

7. Pathogenesis & Clinical features

8. Aspergillosis
• Infection by : inhalation of the conidia;
• Atopic individuals often develop severe allergic reactions to the
conidial antigens
• In immuno- compromised patients—especially those with leukemia,
stem cell transplant patients, and individuals taking corticosteroids—
the conidia may germinate to produce hyphae that invade the
internal organs and other tissues.

9. Pathogenesis:
• In the lungs, alveolar macrophages are able to engulf and destroy the
conidia.
• But macrophages from corticosteroid-treated animals or
immunocompromised patients have a diminished ability to contain
the inoculum.
• In the lung, conidia swell and germinate to produce hyphae that have
tendency to invade pre existing cavities (aspergilloma or fungus ball)
or blood vessels.

10. Clinical features:
1. Allergic bronchopulmonary aspergillosis
• Inhalation of spores provoke hypersensitivity reactions ( Type I, Type
lll, combination of both) against Aspergillus antigens
• Recurrent chest infiltration, asthma occurs.
• Difficulty in breathing and permanent lung scarring occurs.
• Fungus grows within the lumen of bronchioles and occluded by fungal
plugs
• Fungus can be demonstrated in sputum.
• Normal hosts exposed to massive doses of conidia can develop
extrinsic allergic alveolitis.
• 2. Aspergilloma
• Colonising aspergillosis
• A fungal balls grows within an existing lung cavity due to old TB or
bronchiectasis.
• Some patients are asymptomatic; others develop cough, dyspnea,
weight loss, fatigue, and hemoptysis.
• Treatment – surgical removal
.
3. Invasive aspergillosis
• At first pneumonia occurs, then later they disseminates to brain
kidneys or heart, gastrointestinal tract.
• Fever,cough, dyspnea, hemoptysis - symptoms
• Fatal
• Mainly in immunocompromised individuals (AIDS patients with
reduced CD4 cell count ).
4. Superficial infections ( non- invasive ) of
• External ear – otomycosis
• Eye – mycotic keratitis
• Nasal sinuses

12. Candidiasis ( Candidosis, Moniliasis)
• Candida sp – normal flora of skin, mucous membranes,
gastrointestinal tract.
• C. albicans - dimorphic fungi ( they can also produce true hyphae).
• C. albicans can be distinguished from other species by 2
morphological tests :
1. After incubation in serum at 37°C for 90’; yeast cells of C.albicans
form true hyphae or Germ tube.
2. On nutritionally deficient media Candida albicans produces large
spherical chlamydospores.

13. • Candida glabrata – only yeast cells are produced, no pseudohyphae
• Candida albicans is identified by the production of germ tubes or
chlamydospores. Other Candida isolates are speciated with a battery
of biochemical reactions.
• 2 serotypes are present- Candida albicans A & B
• Candida albicans can cause both infections of skin and mucosa as well
as systemic disease.
• So Candida infection, represents a bridge connecting superficial and
deep myucoses.

14. Pathogenesis:
Superficial (cutaneous or mucosal) candidiasis is established by ,
• an increase in the local census of Candida and
• damage to the skin or epithelium that permits local invasion by the yeasts
and pseudohyphae .
• Systemiccandidiasis occurs when Candida enters the bloodstream and the
phagocytic host defenses are inadequate to contain the growth and
dissemination of the yeasts.
• From the circulation, Candida can infect the kidneys, attachto prosthetic
heart valves, or produce candidal infections almost anywhere (eg, arthritis,
meningitis, endophthalmitis).

15. • Cutaneous or mucocutaneous lesions is characterized by inflammatory
reactions varying from pyogenic abscesses to chronic granulomas. The
lesions contain abundant budding yeast cells and pseudohyphae.
• By administration of oral antibiotics- the number of Candida species
increases in the intestinal tract.
• They can enter the circulation by crossing the intestinalmucosa.
• Candida albicans and other Candidia species produce a family of
agglutinin-like sequence (ALS) surface glycoproteins, some of which are
adhesins that bind host receptors
• They mediate attachmentto epithelial or endothelial cells.

16. Pathogenesis and clinical features
• It causes infection ofthe skin,mucosa and rarelyof the
internal organs
• Opportunisticendogenous infection
1. cutaneous candidiasis
• Intertriginous / paronychial
• Former is erythematous,scalingmoist lesions with sharply
demarcated borders.
• The sites affected – groin, perineum,axillae.
• Occurs mainlyin obese and diabeticpatients
• Paronychia & onychomycosis – occupational,in domestic
workers, bartenders,cooks (due to repeated prolonged
immersion offingers in water)
• Onychomycosis- painful,erythematous swellingofnail
• 2. Mucosal lesions
• Vaginitis / vulvovaginitis – irritation,acidicdischarge, mainly
in pregnancy,diabetes
• Oral thrush – mainlyin bottle fed infants.Creamywhite
patches on tongue or buccal mucosa.
• It can occur in tongue,lips,gums,palate
• It occurs mainlyin AIDS patients
• 3. IntestinaI candidiasis
• Diarrhea
• Due to excessiveoral antibiotictherapy
4. Bronchopulmonary Candidiasis
5. Systemicinfections-septicemia, endocarditis, meningitis
Endocarditis – on prostheticheart valves.Kidneyinfections,
urinaryinfections mayassociatedwith diabetes,pregnancy,
Foleycatheters
6. Candidagranulomaand chronicmucocutaneous candidosis.

17. Chronic mucocutaneous candidiasis
• Rare
• Onset in early childhood
• Associated with cellular immunodeficiencies, endocrinopathies
• Chronic superficial disfigurements on skin, mucosa
• Unable to mount Th17 response to Candida

19. • Cell-mediated immune responses, especially CD4 cells, are important
in controlling mucocutaneous candidiasis, and the neutrophil is
probably crucial for resistance to systemic candidiasis.
• During infections, cell wall components such as mannas,glucans,
glycoproteins, enzymes are released
• They elicit Th1 and Th2 immune responses.
• Antibodies are produced against candidial enolase, heat shock
proteins, secretory proteins etc.

20. Cryptococcosis ( Torulosis )
• Infection acquired by inhalation of desicated yeast cells or basidiospores.
Pathogenesis:
• Primary pulmonary infection may be asymptomaticor mimic influenza -
like respiratory infection, often resolve spontaneously.
• They are neurotrophic yeasts.
• They migrate into central nervous systemand cause meningoencephalitis.
• They can also infect skin, eyes, prostate etc.
• They are mainly seen in HIV/AIDSpatients, individuals with haematogenous
malignancies, other immunosuppressive conditions.
• 90% of cryptococcosis is caused by C. neoformans.

22. • C neoformans and C. gattii differ from non-pathogenic species by the
abilities to grow at 37°C and the production of laccase, a phenol
oxidase, which catalyzes the formation of melanin if diphenolic
substrate is provided ( colonies produce brown pigment)
• Major virulence factors: Capsule & Laccase .
• 5 serotypes are present : A,B,C,D,AD
• C. neoformans : serotype A ,D,AD
• C. gattii : serotype B or C

23. Clinical features:
• Asymptomaticmostly
1. Pulmonary cryptococcosis – lead to
mild pneumonitis
2. Visceral cryptococcosis – simulate
TB, cancer (bones, joints)
3. Cutaneous cryptococcosis – small
ulcers to large granuloma
4. Cryptococcal meningitis
• Most serious
• It mimic brain tumor, brain abscess,
TB.
• It causes chronic meningitis.
• Headache, neck stiffness,
disorientation occur.
• Onset is insidious
• The course is slow and progressive
• It is often seen in AIDS (58%)
• It does not transmit from person to
person.

25. LAB DIAGNOSIS
SPECIMEN &METHODS ASPERGILLOSIS CANDIDIASIS CRYPTOCOCCOSIS
1. Specimen • Exudate – sputum
• Tissue sections- biopsy,
postmartem materials
• Whitish mucosal
patches
• Skin and nailscrapings
• Sputum
• Urine
• Blood
• CSF
• Blood
• Skin scrapings
2. Microscopy • Wet preparation
( 10% KOH) of exudate
• PAS staining of tissue
sections
- Septate hyaline
hyphaeis observed.
• LPCB
-Septate hyphae and
conidiosporesare seen
• Wet preparation
• Gram staining –
Budding Gram positive
cells
• Increased presence is
only significant
• Demo. of mycelial
forms indicate
colonisation &tissue
invasion- significant
• Indianink staining–
capsulated,budding
yeast cells

26. Asperillus fumigatus
Wet mount
preparation
PAS staining

27. Candida
albicans

28. Cryptococcus
neoformans

29. 3. Culture SDA - after 3-4 days
incubationat 25-37°C
Coloured colonies with a
velvetytopowdery
surface.
A. fumigatus –dark green
A. niger – black
A. flavus – yellow green
• SDA – creamy white,
smooth and yeasty
odour
• Corn meal agar(20°C)-
chlamydospores
• Reynolds – Braude
phenomenon- germ
tubes are formed
within 2 hourswhen
incubatedin human
serum at 37°C
SDA – smooth, mucoid,
cream coloured colonies.
On an appropriate
diphenolicsubstrate,the
phenol oxidase (or
laccase) of C. neoformans
and C. gattii produces
melaninin
the cell walls and colonies
developa brown pigment.
4. Serology • Antibodytests are not
helpful in the diagnosis
of invasiveaspergillosis
but detection of beta-
glucan is useful
Not helpful Demonstrationof the
capsular antigen by
precipitation,latex
agglutinationtests –
indicativeof cryptococcal
meningitis

30. 1
2
2

31. Skin test • ID injection of
Aspergillus spp
• Immediate type skin
test reaction- after 15 ‘
• Arthur’s type – after 4-
6 hours
• To diagnose allergic
broncho pulmonary
aspergillosis
• Candida extracts are
injected
• Delayed
hypersensitivityoccurs
• Indicatorof functional
integrity of CMI
Animal inoculation • IC or IP inoculation
into mice
• Capsulatedbudding
yeast cells –
demonstrated- in the
brain of infected mice
Biochemicaltests - -

34. • CHROMagar Candida can easily identify three species of Candida-
• on the basis of colonial color and morphology, and
• accurately differentiate between them i.e. Candida albicans, Candida tropicalis,
and Candida krusei.
• The specificity and sensitivity of CHROMagar Candida for C. albicans calculated
as 99%, for C. tropicalis calculated as 98%, and C. krusei it is 100%.

36. Epidemiology
Aspergillosis Candidiasis Cryptococcosis
• Avoidexposure to conidiaof
Aspergillus.
• Bone marrow transplantunits
employ filtered air conditioning
systems, reduce visits, to
minimize exposure to conidiaof
Aspergillus and other molds.
• Patients at high risk are given
pro- prophylacticlow dose of
AmphotericinB & Itraconazole
• The most important preventive
measure is - to avoiddisturbing
the normal balance of microbiota
and intact host defenses.
• Candidiasisis not communicable
• Outbreakscaused by the
nosocomialtransmission of
particular strains to susceptible
patients (e.g., leukemics,
neonates, ICU patients).
• Bird droppings – reservoir of
infection
• Birds are not infected
• Patients with AIDS, hematologic
malignancies,patientsmainted
on corticosteroidsare highly
susceptible
• Mostly caused by serotype A

37. TREATMENT
Aspergillosis Candidiasis Cryptococcosis
• Invasive
aspergillosis-
Amphotericin B
(IV)
• Voriconazole (IV)
• Normally –
Nystatin
• Disseminated
cases –
a. Amphotericin B
b. 5- fluorocytosine
c. Triazoles
(itraconazole,
Voriconazole) ,
d. Imidazole
(ketoconazole)
• Amphotericin B
• 5 – fluorocytosine
• Triazoles
(itraconazole,
Voriconazole)
• Imidazole
(ketoconazole)

38. References
• Ananthanarayan and Paniker’s Microbiology, 9th Edition, p. no : 605-
614
• Essentials of Medical Microbiology, Apurba Shankar Sastri, 1st Edition,
p.no : 566-573
• Medical Microbiology, Jawetz,Melnick, Adelberg, 26 th Edition, p.no:
694-701.

39. THANKYOU