mycology lecture for mbbs students

1. SYSTEMIC FUNGAL
INFECTIONS

2. SYSTEMIC MYCOSES
• The infection originates primarily at one site
like lungs and disseminates systemically to
other body sites.
• They are soil fungi

6. HISTOPLASMOSIS
• Unique among pathogenic fungi in that it is an
intracellular parasite.
• Caused by the dimorphic fungus,
• H. capsulatum, H.dubosii(Africa)
Infection is by inhalation-pulmonary disease-
dissemination to RE cells (Phagocytic cells)
• (a) In tissue-as yeast cells in RE cells;
• (b) In nature in mold form with tuberculate
spores (spores with tubercles or finger like
projections)

7. Pathogenesis
• asymptomatic infection,
• ac influenza like illness,
• Chr. Form-resemble TB
• Later it progressive with widespread infection
of RE system
Disseminated infection occurs most often in
old age, infancy, impaired immune response
(due to neutropenia, haematological
malignancy, AIDS and high doses of steroids)

8. (i) In tissue –yeast form
cells found as oval budding
cells; 2-4um; also yeast
forms seen on blood agar
at 370C;
(ii) On Sabouraud’s agar at
room temp-white cottony
mycelial growth with
tuberculate spores (large
thick walled spherical
spores with tubercles or
finger like projections).
Worldwide in distribution,
most common in USA.

9. Lab diagnosis
• Microscopy after Giemsa/,
Wright-of sputum, pus, blood
(AIDS),
• culture on Sabouraud’s (25-300C)
• histoplasmin skin testing-
delayed hypersensitivity test
• Liver,lung biopsy-PAS,
Methenamine silver
• Culture at 370C used for
conversion from mold to yeast-
for confirmation
• Serological test-CFT, Latex
agglutination

11. BLASTOMYCOSIS
(North America Blastomycosis)
• Dimorphic fungus Blastomyces
dermatitidis ;
• causes suppurative granulomatous
lesions of skin and lungs.
• Seen in North America & Africa;
• Source–soil-inhalation-lungs-
dissemination.
• In tissue and culture at 370C budding
yeasts with double contoured walls
and a single broad based bud, from
a single pole on the mother cell.
• On culture at room temp it gives rise
to filamentous septate hyphae.

12. BLASTOMYCOSIS/Pathogenesis
• Slowly progressive disease, chest radiography
resembles TB, Malignancy
• Disseminated disease seen in
immunosuppressed
• Skin lesions are raised and well demarcated

13. Lab diagnosis
• Direct microscopy of pus, scrappings from skin
lesions or sputum-thick walled yeast cells with
buds on a broad base,
• The buds remain attached until they are
almost the size of parent cell forming chain of
3 or 4 cells

15. PARACOCCIDIOIDOMYCOSIS/South American
blastomycosis
• Is caused by a dimorphic fungus
Paracoccidioides brasiliensis - Chr
granulomatous disease of skin, mucosa,
lymphnodes and internal organs.
• Disease confined to South America.
• The yeast phase is found in tissue and
culture at 370C which is spherical, thick
walled cell, with multiple buddings, ship
steering wheel appearance;
• at room temp mycelial form develops.
Paracoccidioides
brasiliensis

16. Lab diagnosis
• Yeast-multiple
buddings- ship steering
wheel appearance
• Skin test
• Serological test-
precipitin, CFT
Paracoccidioides brasiliensis

17. COCCIDIOIDOMYCOSIS
• Is caused by dimorphic fungus
Coccidioides immitis ,
• Seen in South Western USA-dry
region; Infection is acquired by
inhalation.
• Disease resembles clinically and
histologically disseminated
tuberculosis.
• Tissue form (Yeast phase) is a
spherule with thick doubly
refractile wall and is filled with
endospores, occurs at-370C.
Coccidioides immitis

18. Coccidioides immitis
Mold

22. OPPORTUNISTIC MYCOSES

23. OPPORTUNISTIC MYCOSES
• immuno-compromised individuals and are rare in
normal individuals
• Incidence of opportunistic mycoses increasing
due to-
(a) Use of immunosuppressive drugs in organ
transplantation
(b) Chemotherapy in cancer treatment
(c) Immunodeficiency due to HIV infection/AIDS
• Constitute 15% of all nosocomial infections in
ICUs

24. SN Opportunistic
mycoses
Causative
agent
Group
1 Candidiasis Candida
albicans
Yeast like
fungus
2 Cryptococco
sis
Cryptococc
us
neoformans
True Yeast
3 Pneumocyst
is carinii
Pneumonia
(PCP)
Pneumocys
tis carinii
Taxonomic
status?(mole
culr-fungus)
4 Aspergillosis Aspergillus
fumigatus
Filamentous
mould

25. • .
•
5 Mucormycosis
(zygomycoses,
phycomycose
s)
Rhizopus,
Absidia &
Mucor spp
Filamentous
mould (non
septate)
6 Penicillosis Penicillium
marneffei
Dimorphic
fungus
7 Histoplasmosi
s
Histoplasma
capsulatum
Dimorphic
fungus

26. CRYPTOCOCCOSIS
• Cryptococcus neoformans- subacute / chr.
infection. Soil saprophytes; abundant in faeces
of pigeons / birds.
• Infection : is by inhalation; Worldwide in
distribution.
• Four serological types of cryptococcal capsular
polysaccharide–A,B,C,& D
• Cryptococcal meningitis is the most serious
type of infection – often seen in AIDS.

27. CRYPTOCOCCOSIS
• Birds do not get infected due to high body
temperature
• C. neoformans var neoformans-(A,D) &C
• C. neoformans var gatti-(B,C)
• Pathogenesis-
(a)Commonest form-self limiting pulmonary form,
Causing, Acute pneumonic type,
(d) Meningeal form.

28. • *Caused by true yeast-Cryptococcus
neoformans. Found worldwide.
• *Round or oval budding yeast cell with
thick prominent polysaccharide capsule.
• *Organism is especially abundant in soil
containing bird (especially pigeon)
droppings.
• *Cryptococcal meningitis is the most
serious form of disseminated infection.

29. Laboratory diagnosis-CRYPTOCOCCOSIS
• India ink / Nigrosine – Capsule +
• Ability to grow at 370C : smooth, mucoid cream coloured
colonies
• Hydrolyse urea
• Budding yeast – Grams stain, wet mount
• Tissue section – PAS
• Serological test for capsular antigen
Cryptococcus gram stain Capsulated yeast in India Ink
preperation
Cryptococcus
neoformans
on Niger
seed agar

30. CANDIDIASIS
• Caused by yeast like fungus Candida albicans
(resembles like pseudohyphae). Part of normal body
flora.
• (a) Oral candidiasis (Thrush)-raised white paques
over oral mucosa, tongue and gums. Presence of
oesophagial candidiasis is a hallmark of progression
of HIV infection to AIDS.
• (b) Vaginal candidiasis- Itching and burning pain of
vulva & vagina with whitish discharge. Infection is
recurrent in HIV +ve women

31. CANDIDIASIS (CANDIDOSIS, MONILIASIS)
• (c) Systemic candidiasis- Potentially life threatening.
May involve GIT, brain, liver, kidney & spleen etc.
Common sign of deep candidiasis-
• Candida endocarditis in surgery/ in drug addicts.
• Cadidaemia in postoperative/immunosuppressed pts

32. MOST COMMONLY ISOLATED
CANDIDA SPECIES
• C. albicans
• C. tropicalis
• C. parapsilosis
• C. kefyr
• C. glabrata
• C. krusei
• C. guillermondii
• C. lusitaniae

33. Lab diagnosis
(a) Microscopy-wet mount and Grams stain;
(b) Culture on Sabouraud’s/blood agar;
(c) Germ tube formation in serum at 370C and
(d) Chlamydospore fomation if cultured on
corn meal agar.
(e) Serology-immunodiffusion,CIE,ELISA
(f) PCR

34. ASPERGILLOSIS
Caused primarily by Aspergillus
fumigatus, ubiquitous, filamentous
septate mould. Rarely pathogenic
in normal host
• Disease manifests as
(a) Pulmonary aspergillosis-
(i) Aspergillus asthma
(ii) Bronchopulmonary
aspergillosis
(iii) Aspergilloma (fungus
ball)

35. aspergillosis
(b) Disseminating aspergillosis- Invasive
aspergillosis of lung then dissemination to
brain, kidney other organs etc.
Diagnosis -Aspergillus hyphae
characteristically form ‘V’ shaped branches
(septate hyphae that branch at 450 angle)

36. Aspergillus

37. Lab diagnosis
• Direct microscopy
• Culture-SDA
• A fumigatus grows at 450C
• Skin test
• Serological test
• PCR

38. MUCORMYCOSIS
• Ubiquitous in nature. Infection
occurs worldwide-they are
saprophytic
• Most common form of disease
which can be fatal within a week
is Rhinocerebral mucormycosis in
which infection begins in the
nasal mucosa or sinuses and
progresses to the orbits, the
palate and the brain. The disease
is aggressive and fatal.
• Broad aseptate hyphae, and form
angled branches
• Species are rhizopus, mucor and
absidia.
• Can be cultured in Sabouraud’s
agar without cycloheximide.

39. • Penicillium marneffei is an
important opportunistic
pathogen in HIV infected.
• Penicillium marneffei cause
serious disseminated
disease with characteristic
papular skin lesions in AIDS
pts of South East Asia
• Diagnosis-brush like
arrangement of conidia-
(penicillium=brush)-chains
of spores from the ends of
short branches of
conidiophores
conidiophores
PENICILLIOSIS

40. Other opportunistic mycoses
• Sporotrichosis- Sporothrix schenkii (brain &
skin)
• Dermatophytoses (Nail & skin)
(a) Trichophyton spp.
(b) Epidermophyton floccosum