Oerview Of Mycology

GENERAL MYCOLOGY
• Medical mycology - branch of medical science thatdeals with the
study of medically important fungi
• ‘fungus’ is derived from Greek ‘mykes’ meaning mushroom (a type of
edible fungus)
Essentials of Medical Microbiology

Fungi differ from bacteria & other eukaryotes
• Eukaryotic and possess eukaryotic cell organelles
• Possess a rigid cell wall, composed of chitin, β-glucans and other
polysaccharides
• ™Cell membrane contains ergosterol instead of cholesterol
• May be unicellular or multicellular
• Lack chlorophyll and divide by asexual and/or sexual means by
producing spores

Morphological Classification of Fungi
1. Yeast: Round to oval cells that reproduce by budding
- Cryptococcus neoformans (pathogenic)
- Saccharomyces cerevisiae (non-pathogenic)
2. Yeast-like: Yeasts forming pseudohyphae (e.g. Candida)
- Differentiated from true hyphae as they have constrictions
at septa
3. Molds: long branching filaments called hyphae
- Hyphae - septate or nonseptate

Morphological forms of fungi

Classification of Fungi
• Based on the growth pattern in culture medium
• Aerial mycelium: It is the part of the mycelium which projects above
the surface of culture medium
• Vegetative mycelium: It is the part of the mycelium that grows on
the surface of the culture medium

Morphological Classification of Fungi
4. Dimorphic fungi: exist as molds (hyphal form) in the environment at
ambient temperature (25°C) and as yeasts in human tissues at body
temperature (37°C)
- Histoplasma capsulatum
- Blastomyces dermatitidis
- Coccidioides immitis
- Paracoccidioides brasiliensis
- Penicillium marneffei
- Sporothrix schenckii.

Taxonomical Classification
• Based on the production of sexual spores
1. Phylum zygomycota: sexual spores – zygospores, and possess
aseptate hyphae, e.g. Rhizopus and Mucor.
2. Phylum ascomycota: Sexual spores - ascospores and possess
septate hyphae, e.g. Aspergillus.
3. Phylum basidiomycota: Sexual spores - basidiospore e.g.
Cryptococcus
4. Phylum deuteromycota (Fungi imperfecti): sexual state is either
absent or unidentified yet

Types of fungal spores
Sexual Spore Observed in-
Zygospores Zygomycetes
Ascospores Aspergillus
Basidiospores Cryptococcus
Asexual Spore Observed in
Vegetative asexual spore
Arthrospore Coccidioides Trichosporon
Blastospore Candida
Chlamydospore Candida albicans

Types of fungal spores
Aerial asexual spore
Conidiospore or conidia Aspergillus
Sporangiospore Zygomycetes
Microconidia Dermatophytes
Macroconidia Dermatophytes

CLASSIFICATION OF FUNGAL DISEASES
Superficial mycoses Agents
Tinea versicolor Malassezia furfur
Tinea nigra Hortaea werneckii
Piedra Trichosporon beigelii, Piedraia hortae
Dermatophytosis Trichophyton, Microsporum, Epidermophyton
Subcutaneous mycoses
Mycetoma Madurella mycetomatis, Pseudallescheria boydii,
etc
Sporotrichosis Sporothrix schenckii
Chromoblastomycosis Phialophora verrucosa Fonsecaea pedrosoiEssentials of Medical Microbiology

Systemic mycoses
Histoplasmosis Histoplasma capsulatum
Blastomycosis Blastomyces dermatitidis
Coccidioidomycosis Coccidioides immitis
Paracoccidioidomycosis Paracoccidioides brasiliensis

Opportunistic mycoses
Candidiasis Candida albicans, Other Candida species
Cryptococcosis Cryptococcus neoformans
Zygomycosis Rhizopus, Mucor, Absidia
Aspergillosis Aspergillus flavus, Aspergillus fumigatus,
Aspergillus niger
Penicilliosis Penicillium marneffei, Other Penicillium species
pneumocystosis Pneumocystis jirovecii
Mycotoxicoses

LABORATORY DIAGNOSIS OF FUNGAL DISEASES
• Specimen Collection
- Depends on site of infection - skin scraping, hair, nail, sputum, etc.
- Systemic mycoses - blood sample, Cerebrospinal fluid (CSF), etc

Microscopy
• Demonstration of Fungal elements in the
specimen
• ™Potassium hydroxide (KOH) preparation:
Keratinized tissue specimens treated with
10% KOH  digests keratin  fungal hyphae
clearly seen
• 20–40% KOH - nail & hair

Microscopy
 KOH preparation
• „Biopsy specimens - dissolved in 10% KOH in a test tube and examined after
overnight incubation
• „Glycerol (10%) can be added to prevent drying
• „DMSO (dimethyl sulfoxide) - help in tissue digestion
™Lactophenol cotton blue (LPCB):
- Phenol acts as disinfectant
- Lactic acid preserves the morphology of fungi
- Glycerol prevents drying
- Cotton blue stains the fungal elements blue

Microscopy
• Gram stain: yeasts & yeast like fungi appear
as gram-positive budding yeast
• ™India ink and nigrosin stains: negative stains
for demonstration of capsule of Cryptococcus
neoformans
• Calcofluor white stain: more sensitive
- Binds to cellulose and chitin of fungal cell wall
and fluoresce under UV light

Histopathological stains
• ™For demonstrating fungal elements from biopsy tissues
• „Periodic acid schiff (PAS) stain:
- PAS positive fungi appear magenta/deep pink, whereas the nuclei
stain blue
- PAS which stains only the live fungi
• „Masson fontana stain: for pigmented (or pheoid) fungi
• „Hematoxylin and Eosin stain
• Mucicarmine stain: for staining the carminophilic cell wall of
Cryptococcus and Rhinosporidium

Histopathological stains
• Gomori methenamine silver (GMS) stain:
- Alternative to PAS
- Stains both live and dead fungi
- Stains the polysaccharide component of the cell wall
- Fungi appear black & background pale green color„

Culture Media
• ™Sabouraud’s dextrose agar (SDA):
- Most commonly used medium
- Contains peptone (1%), dextrose (4%) and pH of 5.6
- May not support some pathogenic fungi
• ™Neutral SDA (Emmons’ modification):
- Differs from original SDA in having neopeptone (1%) and dextrose
(2%) and pH of 7.2

Culture Media
• ™Corn meal agar and rice starch agar: Nutritionally deficient media
used for stimulation of chlamydospore production
• ™Brain heart infusion (BHI) agar and blood agar: Enriched media, used
for growing fastidious fungi like Cryptococcus and Histoplasma
• ™Niger seed agar and bird seed agar: selective growth of Cryptococcus
• ™CHROMagar Candida medium: selective as well as differential
medium for speciation of Candida

Culture Condition
• ™Temperature: Most of the fungi grow well at 25–30°C except the
dimorphic fungi that grow at both 25°C and 37°C
• ™BOD incubators (biological oxygen demand): capable of maintaining
low temperature
• ™Incubation time: 2–3 weeks
• ™Antibiotics - cycloheximide (actidione), chloramphenicol and
gentamicin - added to the culture media to inhibit bacterial growth

Culture Identification
• Based on macroscopic appearance of the colonies grown on
culture and microscopic appearance
• Macroscopic Appearance of the Colony
• ™Rate of growth:
- Rapid growth (<5 days) - saprophytes, yeasts and agents of
opportunistic mycoses
- Slow growth (1–4 weeks): dermatophytes, agents of
subcutaneous and systemic mycoses

Culture Identification
• ™Pigmentation: reverse side of the culture media
• ™Texture: Refers to how the colony would have felt if allowed to touch
- glabrous (waxy/leathery), velvety, yeast like, cottony or
granular/powdery
• ™Colony topography: rugose (radial grooves), folded, verrucose or
cerebriform (brain-like)

Microscopic Appearance of Fungi
• ™Teased mount:
- LPCB tease mount
- Identification is based on :
- „Nature of hyphae (septate or aseptate,
hyaline or phaeoid, narrow or wide)
and „Type of sporulation (conidia or
sporangia)
• ™Slide culture: in situ microscopic
appearance of the fungal colony

Microscopic Appearance of Fungi
• Cellophane tape mount:
- Impressions taken by placing the cellophane tape on the
colonies  LPCB mount is made
- Easy to perform than slide culture and in-situ fungal
morphology maintained

Other Methods of Identification
• ™For Candida: Germ tube test, Dalmau plate culture, carbohydrate
fermentation and carbohydrate assimilation tests are done
• For dermatophytes: Hair perforation test, dermatophyte test
medium and dermatophyte identification medium are used
• ™Urease test can be done for the fungi that produce urease enzyme,
e.g. Cryptococcus

• Immunological Methods - to detect antibody or antigen
from serum and/or other body fluids
• Antibody detection - ELISA, immunodiffusion test,
agglutination test, and complement fixation test (CFT)
• Antigen detection - latex agglutination test for cryptococcal
antigen from CSF
• ™Immunohistochemistry: detecting antigens (e.g. proteins)
on cells of a tissue section

• Tests for Metabolites - in body fluids by gas liquid chromatography
• Tests to Demonstrate Delayed Hypersensitivity
- Skin tests - Histoplasma, Blastomyces, Coccidioides, Paracoccidioides,
Dermatophyte, Sporothrix and Candida.
• Molecular Methods
- Polymerase chain reaction (PCR) and its modifications
- DNA sequencing methods

Antifungal Agents
Class Drug Mechanisms Use
Antifungal Antibiotics
Polyenes
Amphotericin B
(AMB)
Bind to
ergosterol and
disrupts fungal
cell membranes
Systemic mycoses
Nystatin,
Hamycin
Topical use (skin
infection)
Echinocandins Caspofungin,
micafungin
Inhibits β-glucan
synthesis in
fungal cell wall
Systemic mycoses

Synthetic Antifungals & their uses
• Azoles - Inhibit ergosterol synthesis of fungi
Imidazoles: Clotrimazole,
miconazole, ketoconazole,
oxiconazole
Topical use (except, ketoconazole can be used for
both topical and systemic use)
Triazoles Systemic mycoses (invasive fungal infections)
Itraconazole Sporothrix, chromoblastomycosis, dermatophytes,
Cryptococcus, Candida (except C. krusei, C.
glabrata) and Trichosporon
Fluconazole Cryptococcus & Candida (ext C. krusei, C. glabrata)
Voriconazole, osaconazole,
isavuconazole
All invasive fungal infections except mucormycosis

Synthetic Antifungals & their uses
Class Drug Mechanisms Use
Antimetabolite Flucytosine (5-FC) Inhibits DNA
synthesis in
fungi; 5-FC is
converted to
fluorouracil,
which inhibits
thymidylate
synthetase
Systemic mycoses
Used in
association with
AMB
Allylamines Terbinafine Inhibits
ergosterol
synthesis of fungi
Topical use

SUPERFICIAL MYCOSES

Tinea Versicolor (pityriasis versicolor)
• Agent: lipophilic fungus Malassezia furfur
• Clinical Manifestation
- Flat-round scaly patches of hypo- to
hyperpigmentation of skin
- Lesions are non-inflammatory and non-
pruritic (or rarely pruritic)
• Areas rich in sebaceous glands - neck,
chest, or upper arms™

Clinical Manifestations
• Seborrheic dermatitis
- Erythematous pruritic scaly lesions - dandruff in adults and cradle
cap in babies
- Severe in patients with AIDS
• ™Atopic dermatitis
• ™Folliculitis
• ™Disseminated infection - rarely

Laboratory Diagnosis
• Mostly clinical diagnosis
• Sample: Skin scrapings
• ™Direct microscopy:
- KOH - Mixture of budding yeasts and
short septate hyphae are seen -
spaghetti and meatballs appearance

Tinea Versicolor
• Culture: SDA with olive oil overlay - ‘fried egg’ colonies appear after
incubating for 5–7 days at 32–35°C
• ™Urease test: positive
• ™Wood’s lamp examination: golden yellow fluorescence.
• Treatment Tinea versicolor
- Topical lotions - selenium sulfide shampoo, ketoconazoleshampoo or
cream, terbinafine cream - 2 weeks

TINEA NIGRA
• Painless, black, non-scaly patches present on palm and sole
• More common in females
• Caused by Hortaea werneckii
• Black-colored yeast like fungus

PIEDRA
White Piedra
• White nodules are formed on the hair
shaft, which are less firmly attached
• ™Agent: Trichosporon beigelii
- Urease positive, yeast like fungus
- Produces creamy white colonies, containing
hyaline septate hyphae intervening with
rectangular arthrospores

Piedra
Black Piedra
• Black nodules, which are firmly attached to the hair
shaft
• Agent: Piedraia hortae
• ™Phaeoid fungus
• Reddish brown colonies; containing dark brown
thick septate hyphae with ascus containing
ascospores

DERMATOPHYTOSES
• Dermatophytoses (or tinea or ringworm) is the most
common superficial mycoses affecting skin, hair and nail
• Dermatophytes - Group of related fungi that are
capable of infecting keratinized tissues
- Trichophyton species: Infect skin, hair and nail
- Microsporum species: Infect skin and hair
- Epidermophyton species: Infect skin and nail

Classification of dermatophytes based on their
usual habitat
Trichophyton Microsporu
m
Epidermoph
yton
Anthropo
philic
T.rubrum
T.mentagrophytes
T.schoenleinii
T.tonsurans,
T.violaceum
M. audouinii E.floccosum
Zoophilic T.equinum
T.verrucosum
M.canis
M.equinumEssentials of Medical Microbiology

Pathogenesis
• Acquired by direct contact with soil, animals or humans infected with fungal
spores
• Predisposing factors - moist humid skin and tight ill-fitting underclothing
• ™Skin: Grow in a centrifugal pattern in the stratum corneum  annular- or
ring-shaped pruritic scaly skin lesions with central clearing and raised edges
• ™Nails: Invade nails through lateral or superficial nail plates and then spread
throughout the nails
• ™Hair shafts: invade the hair shaft or may be found surrounding it. Hairs
become brittle and areas of alopecia may appear

Pathogenesis
• Lesions - not by the tissue invasion by the fungi per se; but
in response to the host’s inflammatory reaction elicited by
fungal antigens
• ™Males more commonly infected as progesterone is inhibitory
to dermatophyte growth
• ™Severity depends on the infecting fungi, immune status of
the host and the site of lesion

Pathogenesis
• „Anthropophilic dermatophytes – Commonest, cause relatively mild
and chronic lesions but respond poorly to treatment
• Geophilic and zoophilic species - less adapted to human, produce
more acute inflammatory response and severe infections; but they
tend to resolve more quickly

Clinical types of dermatophytoses
Tinea capitis
Kerion Painful inflammatory reaction producing boggy lesions on scalp.
Agent- T.verrucosum
Favus Cup like crust (scutula) forms around the infected hair follicle
with minimal hair shaft involvement.
Agent: T.schoenleinii
Ectothrix Arthrospore formation occurs on the surface of hair shaft
(M.audouinii, M.canis, and T.mentagrophytes)
Endothrix Arthrospore formation occurs within the hair completely filling
hair shaft (T.tonsurans & T.violaceum)

Clinical Types Area involved
Tinea corporis Infection of the non hairy skin of the body
(trunk and limbs)
Tinea pedis
(Athlete foot)
Infect first the webs between the toes, then
spread to the sole in a "moccasin" pattern
Tinea cruris
(or jock itch)
Infection of the groin area
Tinea barbae Infection of the beard and moustache area of
face
Tinea faciei Infection of the non-bearded area of face

Clinical Types Area involved
Tinea imbricata Concentric lesions of the skin
Agent- T.concentricum
Tinea unguium (nail
plate infection)
Infection of nail beds
Agent- T.mentagrophytes & E.floccosum
Tinea manuum Infection of the palmar aspect of hands

Ring worm infections
A. Tinea capitis
B. Tinea faciei
C. Tinea pedis
D. Tinea corporis
A B
C
D

Dermatophytid or Id Reaction
• Hypersensitivity to dermatophyte antigens  secondary eruption in
sensitized patients
• Lesions - distinct from the primary ringworm lesions
• Occur distal to primary site and fungal culture often turns negative

• Woods Lamp Examination
• Positive for various Microsporum species &Trichophyton schoenleinii
• Fluorescence is due to the presence of pteridine pigment in cell wall
• Skin scrapings, hair plucks (broken or scaly ones) and nail clippings
from the active margin of the lesions

Direct Examination
• KOH mount or calcofluor white stain - thin
septate hyaline hyphae with arthroconidia
• Hair – arthroconidia on the surface of shaft
(ectothrix) or within the shaft (endothrix)

Culture
• Medium: SDA containing cycloheximide and incubated at 26–28°C for
4 weeks
• Potato dextrose agar – better sporulation
• Identification is made by:
• Macroscopic appearance of the colonies - rate of growth, texture,
pigmentation, colony topography ™

Colony morphology of dermatophytes
Trichophyton mentagrophytes Microsporum canis Epidermophyton floccosum

Microscopic identification
• Microscopic appearance: LPCB tease mount - hyphae and spores (or
conidia)
- Conidia:
- Microconidia - small unicellular
- Macroconidia – Multicellular, septate
• Special hyphae: hyphae such as spiral hyphae, racquet hyphae and
favic chandeliers

Microscopic identification
Dermatophytes Macroconidia Microconidia
Trichophyton Rare, thin walled,
smooth, pencil shaped
Abundant
Microsporum Numerous, thick
walled, rough, spindle
shaped
Rare
Epidermophyto
n
Numerous, smooth
walled, club shaped
Absent

Characteristic features of dermatophytes

LPCB Tease Mounts
Trichophyton mentagrophytes Microsporum canis Epidermophyton floccosum

Identification of dermatophytes
Dermatophy
tes
Macroscopic
appearance
Microscopic appearance
T.rubrum Velvety, red
pigment on
reverse
Microconidia- tear drop shaped, plenty
Macroconidia- few, long, pencil shaped
T.Mentagrop
hytes
White to tan
powdery
Pigment variable
Microconidia- numerous, round to
pyriform
Macroconidia- cigar shaped
Spiral hyphae seen
T.schoenleini
i
Smooth, waxy Microconidia & macroconidia- rare or
absent. Chlamydospores seenEssentials of Medical Microbiology

Dermatophy
tes
Macroscopic
appearance
T.violaceum Slow growing,
waxy
Violet pigment
on reverse
Microconidia & macroconidia- rare or
absent
Distorted hyphae seen
Chlamydospores seen
M. audouinii Slow growing,
velvety,
brownish
Thick walled chlamydospores seen
Macroconidia and microconidia- rare
M. gypseum Buff colored,
powdery
Macroconidia- abundant, thick walled,
spiny, spindle shaped, 4-6 septa, roundedEssentials of Medical Microbiology

Dermatophy
tes
Macroscopic
appearance
M.canis Cottony, orange
pigment on
reverse
Macroconidia- abundant, thick walled,
spiny, spindle shaped, up to 15 septa,
pointed ends
E.floccosum Powdery, folded,
yellowish green
Macroconidia club or clavate shaped in
clusters, 4-6 septa
Microconidia- absent

Other Methods of Diagnosis
• Hair perforation test:
- Fungi pierce hair producing wedge-shaped perforations
- Positive – T.mentagrophytes and M.canis
• ™Urease test: Trichophyton mentagrophytes is urease positive
• ™Dermatophyte test & Dermatophyte identification
medium: for presumptive identification - based on color
change
• ™Molecular methods: PCR
• ™Skin test: detects hypersensitivity to trichophytinEssentials of Medical Microbiology

Treatment
• Oral terbinafine or itraconazole - drugs of choice f
• Duration – depends on the affected site (1–2 weeks for skin lesions, 6
weeks for hair infection, 3 months for onychomycosis)
• Pulse therapy
• ‰Alternative: Oral griseofulvin and ketoconazole
• ‰Topical lotion - whitfield ointment or tolnaftate

SUBCUTANEOUS MYCOSES

SUBCUTANEOUS MYCOSES
• The agents of subcutaneous mycoses usually inhabit the soil
• They enter the skin by traumatic inoculation with contaminated
material
• Tend to produce granulomatous lesions in the subcutaneous tissue

MYCETOMA
• Chronic, slowly progressive granulomatous infection of the skin and
subcutaneous tissues
• ™Triad: Swelling, discharging sinuses and presence of granules in the
discharge
• ™Also known as Maduramycosis or Madura foot, as it was first
described in Madurai, South India, by John Gill (1842)

Types of Mycetoma and Causative Agents
• Eumycetoma – caused by fungi
• Actinomycetoma – Caused by bacteria
• Botryomycosis - mycetoma like condition caused by some bacteria
such as Staphylococcus aureus.

Organisms causing Mycetoma
Eumycetoma Actinomycetoma
Black granules-
Madurella mycetomatis
Madurella grisea
Exophiala jeanselmei
Curvularia species
White granules-
Pseudallescheria boydii
Aspergillus nidulans
Acremonium species
Fusarium species
White to yellow granules-
Nocardia species- Most common
agent
Streptomyces somaliensis
Actinomadura madurae
Pink to red granules-
Actinomadura pelletieri

Pathogenesis
• Accidental trauma (thorn prick or splinter injury)
 Organisms enter the skin or subcutaneous tissue from
contaminated soil
 micro abscesses by polymorphs
 chronic granulomatous tissue in skin and subcutaneous tissues

• Clinical triad
1. Tumor like swelling (tumefaction)
2. Discharging sinuses
3. Discharge oozing from sinuses containing
granules
• Commonest site – Feet
• Osteolytic or osteosclerotic bony lesions
• Usually painless

Eumycotoma v/s Actinomycotoma
Features Eumycotoma Actinomycotoma
Tumor Single, well defined
margins
Multiple tumour masses with
ill defined margins
Sinuses Appear late, few in
number
Appear early, numerous with
raised inflamed opening
Discharge Serous Purulent
Grains Black/white White/ red
Bone Osteosclerotic lesions Osteolytic lesions
Grains contain fungal hyphae (>2um) Filamentous bacteria (< 2um)

Epidemiology
• Endemic in Africa, India, the Central and South America
• ™Globally Actinomycetoma is more common (60%) than eumycetoma
(40%)
• Eumycetoma is more common in Africa
• In India, Rajasthan reports the maximum cases of mycetoma per year
followed by Tamil Nadu and West Bengal
• Actinomycetoma predominates in India (65%), except in Rajasthan
where eumycetoma is more common

• Grains collected on sterile gauze by pressing the sinuses from
periphery or by using a loop
• Direct Examination
• Granules washed in sterile saline; crushed between the slides and
examined
• ™Macroscopic appearance of granules - color, size, shape, texture

• ™Suspected Eumycetoma :
- KOH mount - hyphae of 2–6 μm width along with chlamydospores at
margin
• ™Suspected Actinomycetoma:
- Gram staining - filamentous gram positive bacilli (0.5–1 μm wide)
- Modified acid fast stain – Nocardia is weekly acid fast

Histopathological staining of the granules
• „Eumycetoma: granulomatous reaction
with palisade arrangement of hyphae in
the cement substance (A)
• „Actinomycetoma: granulomatous
reaction with filamentous bacteria at the
margin (B)
A
B

Culture
• Granules - best specimen for culture
• Both fungal (SDA) and bacteriological media (Lowenstein Jensen
medium, Blood agar) inoculated
• ™Eumycetoma agents - growth rate, colony morphology, production
of conidia and their sugar assimilation patterns
• ™Agents of actinomycetoma - growth rate, colony morphology, urease
test, acid fastness and decomposition of media containing casein,
tyrosine, xanthine, etc

Treatment
• Surgical removal of the lesion followed by:
• ‰Antifungal agents for eumycetoma (itraconazole or amphotericin B
for 8–24 months)
• ‰Antibiotics for actinomycetoma such as Welsh regimen (amikacin
plus cotrimoxazole)

SPOROTRICHOSIS
• Also known a Rose Gardner’s disease
• Subcutaneous noduloulcerative lesions
• Caused by Sporothrix schenckii, thermally dimorphic fungus
• Pathogenesis
• Minor trauma by thorn prick or splinter injury  Spores of
S.schenckii introduced into skin  Fungal Enzymes help in local
invasion  spread along the lymphatics

• Chronic subcutaneous pyogranulomatous disease
• Incubation period - about 3 weeks
• Lymphocutaneous type: most common type (80%)
- Painless noduloulcerative lesions (sporotrichoid pattern ) along the
lymphatics
- Enlarged Lymph nodes, indurated and have cord like feeling on
palpation

Other clinical types
• Osteoarticular type: seen among alcoholics
• Pulmonary type: following spore inhalation, seen in people with
COPD
• „Disseminated sporotrichosis: in immunocompromised patients
(AIDS)
• „Fixed cutaneous type: Single nodule is found, that is less progressive
and does not spread by lymphatics

Sporotrichoid lymphocutaneous infection
• Syndrome characterized by the development of superficial cutaneous
lesions that progress along dermal and subcutaneous lymphatics
• ‰Common causes: Sporothrix schenckii, Nocardia brasiliensis,
Mycobacterium marinum or Leishmania brasiliensis
• ‰Rare causes: Coccidioidomycosis, cryptococcosis, blastomycosis,
histoplasmosis, anthrax, Burkholderia pseudomallei, lepromatous
leprosy, lupus vulgaris, Francisella tularensis and cowpox virus

Epidemiology
• Tropical countries with high humidity
• World: Central South America, South Africa and India
• ™India: Sub Himalayan hilly areas of northeast states ranging
from Himachal Pradesh to Assam
- Other endemic foci - northern Karnataka and southern
Maharashtra
• ™Source: Decaying vegetations (wood, bark, leaves), and soil
• ™Risk factors - people walking bare foot, certain occupations
such as farmers and gardeners

• Specimens - pus, aspirate from nodules, curettage or swabbing from
ulcers
• ™Direct microscopy: KOH mount or calcofluor staining  elongated
yeast cells of 3–5 μm in diameter
• ™Histopathological staining of tissue sections - cigar-shaped asteroid
bodies
• Asteroid body - central basophilic yeast cell surrounded by radiating
extensions of eosinophilic mass, composed of antigen-antibody
complexes (Splendore-Hoeppli phenomenon)

• Culture: It is the most definitive tool for diagnosis.
• Specimens are inoculated onto SDA and blood agar
• in duplicate and incubated at 25°C and 37°C simultaneously,
• because S. schenckii is a dimorphic fungus
• „. At 25°C: It produces mycelial form, consisting of
• slender delicate hyphae with conidia arranged in
• flower-like pattern (Fig. 52.11B)
• „. At 37°C: It produces yeast form, characterized by
• moist creamy white colonies which turn brown black
• in 10–14 days.

Sporothrix schenckii
Yeast form
(asteroid body)
Mold form showing thin septate hyphae
with flower-like sporulation

Sporotrichosis
• Serology: Latex agglutination test detects serum antibodies in
patients with extracutaneous form of the disease
• ™Skin test: delayed type of hypersensitivity reaction against
sporotrichin antigen
• Treatment Sporotrichosis
• Itraconazole - drug of choice for all forms of sporotrichosis; except for
disseminated form where amphotericin B is recommended
• Duration: 2–4 weeks after the lesions resolve

CHROMOBLASTOMYCOSIS
• Slow growing chronic subcutaneous lesions caused by group of
dematiaceous or phaeoid fungi (i.e. darkly pigmented fungi) that
produce a characteristic morphology called sclerotic body
• ™Agents of chromoblastomycosis:
- Fonsecaea pedrosoi and F. compacta
- Phialophora verrucosa
- Cladosporium carrionii
- Rhinocladiella aquaspersa.

CHROMOBLASTOMYCOSIS
• Lesions - slow growing and polymorphic -
verrucose (most common type), crusted,
ulcerative and nodular or tumor-like
• ™Sclerotic bodies: brown thick walled round cells
(5–12 μm size) with multiple internal transverse
septa
- also called Medlar bodies or muriform cells or
“copper pennies.”

CHROMOBLASTOMYCOSIS
• Tropical or subtropical climates, often in rural areas
• Treatment:
- Surgical removal (cryosurgery or laser therapy) of the lesion followed
by antifungals (itraconazole)

PHAEOHYPHOMYCOSIS
• Chronic subcutaneous lesions, caused by dematiaceous or phaeoid fungi
other than that are described in chromoblastomycosis (i.e. they do not
produce sclerotic bodies)
• They exist in mycelial form
• Caused by:
- Alternaria species
- Bipolaris species
- Curvularia species
- Exophiala jeanselmei
- Cladophialophora bantiana (it is neurotropic, produces brain abscess)

RHINOSPORIDIOSIS
• Chronic granulomatous disease, characterized by large friable polyps
in the nose conjunctiva and occasionally in ears, larynx, bronchus and
genitalia
• ™Agent: Rhinosporidium seeberi, an aquatic protistan parasite
• ™Source: Stagnant water
• ™Distribution: tropical countries, especially in Sri Lanka and India
(Tamil Nadu, Kerala, Odisha and Andhra Pradesh)

RHINOSPORIDIOSIS
• ™Diagnosis - histopathology of the polyps 
spherules (large sporangia up to 350 μm
size, that contain numerous endospores,
each 6–9 μm in size)
• Stained better with mucicarmine stain
• R.seeberi has not been cultivated yet

RHINOSPORIDIOSIS
• Treatment:
• Radical surgery with cauterization is the mainstay of treatment
• Dapsone
• Recurrence is common

SYSTEMIC MYCOSES

HISTOPLASMOSIS
• Systemic granulomatous disease caused by a dimorphic fungus,
Histoplasma capsulatum
• Also known as Darling’s disease
• Three varieties:
1. H. capsulatum var. capsulatum  classical histoplasmosis
(commonest)
2. H. capsulatum var. duboisii  African histoplasmosis
3. H. capsulatum var. farciminosum  epizootic histoplasmosis

H. capsulatum var. capsulatum
• Epidemiology
• Histoplasmosis occurs worldwide
• Endemic in USA, particularly in states bordering the Ohio River valley
and the lower Mississippi River
• In India - reported frequently from the region of West Bengal along
the Ganga River
• The fungus inhabits humid and acidic soil that contains large amount
of bird or bat droppings

Histoplasmosis - Pathogenesis
• Contaminated soil disturbed  inhalation of spores (i.e.
microconidia)  Spores engulfed inside the alveolar
macrophages and then transform into yeast forms  yeasts
survive within the phagolysosome  carried to the lymph
nodes  spread to other parts of the body through
bloodstream
• ™Majority show strong cell-mediated immune response
within 2 weeks Granulomas  heal with fibrosis and
calcification. rarely reactivates
• ™impaired CMI  disseminated infectionEssentials of Medical Microbiology

• Classical histoplasmosis ranges from asymptomatic infection (in
immunocompetent people) to life-threatening illness seen in people
with low CMI
• ™Pulmonary histoplasmosis (MC)
- Acute form - mild flu like illness, pulmonary infiltrates in chest X-ray
with hilar or mediastinal lymphadenopathy
- Chronic cavitary histoplasmosis - in smokers

• Mucocutaneous histoplasmosis: Skin
and oral mucosal lesions secondary to
pulmonary infection
• Oral lesions - in Indian patients
• Disseminated histoplasmosis: if CMI is
very low
- Common sites - bone marrow, spleen,
liver, eyes and adrenal glands

• ™Specimens: sputum, aspirate from bone marrow and lymph node,
blood and biopsies from skin and mucosa
• ™Direct microscopy:
• Histopathological staining (PAS, Giemsa or GMS stain)  tiny oval
yeast cells (2–4 μm size) with narrow-based budding within the
macrophages with an underlying granulomatous response

Culture
• Gold standard method of diagnosis
• Media: SDA, blood agar and BHI agar in duplicate and incubated
simultaneously at 25°C and 37°C
• Histoplasma is a dimorphic fungus
• „At 25°C: mycelial phase - white to buff brown colonies that consist of two
types of conidia or spores:
1. Tuberculate macroconidia, with typical thick walls and finger-like
projections which is a characteristic feature of this fungus
2. Microconidia are smaller, thin, and smooth-walled
At 37°C: yeast form (creamy white colonies

Histoplasma capsulatum

Other Tests
• Serology: Antibodies -CFT and immunodiffusion test
- Antibodies appear after 1 month of infection more useful in
chronic stage
- False positive - past infection or cross infection with Blastomyces
• ™Skin test: delayed type hypersensitivity response to histoplasmin
antigen, which indicates prior exposure.
• ™Molecular test: PCR targeting specific ITS D1/D2 gene

Treatment Histoplasmosis
• Liposomal amphotericin B - acute pulmonary and disseminated
histoplasmosis
• Itraconazole - chronic cavitary pulmonary histoplasmosis

Histoplasma variants
• H. capsulatum var. duboisii
- Causes African histoplasmosis
- Frequent skin and bone involvement
- yeast form exists as large thick walled oval yeast cells (7–15 μm) with
prominent narrow based budding
• H. capsulatum var. farciminosum
- Causes epizootic histoplasmosis
- A form of lymphangitis in horses and mules

BLASTOMYCOSIS
• Also known as North American blastomycosis or Gilchrist’s disease or
Chicago disease
• Caused by - Blastomyces dermatitidis, a dimorphic fungus,
• Pathogenesis
• Transmitted by inhalation of the conidia
• Spores are engulfed by alveolar macrophages, where they get
converted into yeast phase.
• Expresses BAD-1 (B.dermatitidis adhesin-1) an essential virulence
factor and also a major inducer of cellular and humoral immune
responses

• Acute pulmonary blastomycosis - most common form
• Extrapulmonary manifestations :
- Skin involvement - most common extrapulmonary form: verrucous
(more common) or ulcerative type of skin lesions
- Osteomyelitis along with contiguous soft tissue
- Abscesses and draining sinuses
- Prostate and epididymis
- Central nervous system in AIDS patients

Blastomycosis
• Epidemiology
• Endemic in North America, particularly in states bordering the Ohio
River and Mississippi River.

• ™Histopathological staining of the
tissue biopsy specimens: thick-
walled round yeast cells of 8–15 μm
size with single broad-based
budding (figure of 8 appearance)

• ™Culture media - SDA, blood agar and BHI agar are inoculated
- At 25°C, mycelial form - hyphae with small pear-shaped conidia
- At 37°C mold to yeast conversion
• ™Skin test: delayed type hypersensitivity to blastomycin antigen
• ™Antibody detection: Immunodiffusion yeast phase antigens such as
antigen—A, BAD-1 and ASWS antigen

Blastomycosis
• Antigen detection – in urine (more sensitive) and in serum
• ™Molecular methods - DNA probe hybridization and real time PCR
• Treatment Blastomycosis
- Liposomal amphotericin B - drug of choice
- Itraconazole - immunocompetent patients with mild pulmonary or
non-CNS extrapulmonary blastomycosis

COCCIDIOIDOMYCOSIS
• Also called desert rheumatism or Valley fever or California
fever
• Coccidioides has two species - C. immitis and C. posadasii
• Pathogenesis
• Transmitted by inhalation of arthroconidia  lungs, they
enlarge, become rounded, and develop internal septations to
form large sac like structures of size up to 200 μm called
spherules, that encompass numerous endospores rupture
and release packets of endospores  disseminate and develop
into new spherules Essentials of Medical Microbiology

• Most patients are asymptomatic (60%)
• Pulmonary coccidioidomycosis (most common) - pneumonia,
cavities, pleural effusion or nodule formation
• Skin lesions - rashes or erythema nodosum and arthritis
• ™Disseminated form: Males and persons with low CMI - skin, bone,
joints, soft tissues, and meninges

COCCIDIOIDOMYCOSIS
• Epidemiology
• It is endemic in certain parts of Arizona, California, Nevada,
• New Mexico, Texas, Utah and northern Mexico.

• ™Histopathological staining - sputum or
tissue biopsy specimens
• Spherules -large sac like structures (20–80
μm size), have thick, double refractile wall,
and filled with endospores

Culture
• On SDA
- Mycelial growth, described as fragmented hyphae consisting of
barrel-shaped arthrospores with alternate cells distorted (empty
cells)
• „Coccidioides differs from other dimorphic fungi as it grows as mold at
both 25°C and 37°C in usual culture media
• Forms spherules at 37°C in certain special culture media only

Spherules and hyphal forms of Coccidioidis

Other Tests
• Serology: Antibodies - immunodiffusion test and CFT
• Skin test: delayed hypersensitivity reaction indicates past infection
• Treatment Coccidioidomycosis
• Itraconazole - drug of choice
• Diffuse pneumonia with pulmonary sequelae - amphotericin B

PARACOCCIDIOIDOMYCOSIS
• Also known as South American blastomycosis, Lutz-Splendore-de
Almeida disease
• Systemic disease caused by the dimorphic fungus— Paracoccidioides
brasiliensis
• Paracoccidioidomycosis is endemic in Brazil and other South
American countries

Pathogenesis and Clinical Manifestations
• Transmission is by inhalation of spores
1. Acute form (or juvenile type):
- Under 30 years, less common but more severe form
- Disseminated infection involving multiple viscera and is refractory to
treatment
2. Chronic form (or adult form): 90% of cases
- Results from reactivation of quiescent lung lesions
- Less severe form, manifested as progressive pulmonary disease affecting
lower lobes, with fibrosis
• „Skin, oral mucosal lesions and cervical lymphadenopathy

• ™Histopathological staining - pus, tissue biopsies or sputum
- Round thick-walled yeasts, with multiple narrow-necked buds
attached circumferentially  Mickey mouse or pilot wheel
appearance
• ™Culture on SDA yields mycelial form at 25°C which converts into
yeast phase at 37°C when grown in BHI agar supplemented with
blood and glutamine
• ™Serology: Antibodies - immunodiffusion, ELISA using gp43 antigen of
P. brasiliensis
• ™Skin test

Paracoccidioidomycosis

Treatment
• Itraconazole - drug of choice for
• Seriously ill patients - amphotericin B
• Sulfonamides are effective, but the response is slow with frequent
relapses

OPPORTUNISTIC MYCOSES

Opportunistic mycoses
• Caused by
- Fungi normally a part of human anatomical flora (e.g. Candida) or
- Found in nature and frequently isolated as laboratory contaminants
(e.g. Aspergillus, Rhizopus and Penicillium)
• Causing infection in presence of opportunities such as low immunity

CANDIDIASIS
• Yeast like fungus that produces pseudohyphae
• Species of Candida:
- Candida albicans: most common and most pathogenic
- Other Candida species which can occasionally cause infection such
as—C. tropicalis, C. glabrata, C. krusei, C. parapsilosis, C. dubliniensis,
C. kefyr, C.guilliermondii and C. viswanathii

Pathogenesis
• Worldwide in distribution. Most common fungal infection
• Predisposing Factors
- Physiological state: Extremes of age (infancy, old age),
pregnancy
- Low immunity:steroid or immunosuppressive drugs, post-
transplantation, malignancy, HIV-infected people
- Patients on broad spectrum antibiotics
- Others: Diabetes mellitus, febrile neutropenia and zinc or iron
deficiency

Virulence Factors
• ™Adhesins
• ™Enzymes - aspartyl proteinases and serine proteinases - tissue
invasion
• ™Toxins: Glycoprotein extracts of Candida cell wall are pyrogenic
• ™Pseudohyphae: Presence of pseudohyphae indicates active infection
• phenotypic switching - „Ability to transform between three
phenotypic forms in the tissue - yeast (blastospores), pseudohyphae,
and true hyphae

Phenotypic switching of Candida

• Mucosal candidiasis:
- Oropharyngeal candidiasis : white,
adherent, painless patch
- „Vulvovaginitis: pruritus, pain, and vaginal
discharge (whitish curd like in severe cases)
- Balanitis and balanoposthitis
- Esophageal candidiasis

• Chronic mucocutaneous candidiasis
- Infants and children with deficient CMI
- Lesions on hair, nail, skin, and mucous membrane
- Usually resistant to treatment
• Cutaneous candidiasis:
- Intertrigo: erythema and pustules in the skin folds; associated with
tight fitting undergarments and sweating

• Paronychia and onychomycosis
• Diaper candidiasis
• Perianal candidiasis
• „Erosio interdigitalis blastomycetica.
• Generalized disseminated cutaneous candidiasis

• Invasive candidiasis: hematogenous or local spread
- Urinary tract infection
- Pulmonary candidiasis, Septicemia
- Arthritis and osteomyelitis, Meningitis
- Ocular—keratoconjunctivitis and endophthalmitis
- Hepatosplenic candidiasis, Disseminated candidiasis
- Nosocomial candidiasis (mainly by C. glabrata).

• Allergic candidiasis includes:
- Candidid: allergic reaction to metabolites of Candida - vesicular
lesions in the web space of hands and other areas
- Similar dermatophytid reaction
• „Other allergic reactions include: Gastritis, irritable bowel syndrome
and eczema

• whitish mucosal patches, skin
and nail scrapings, sputum,
urine or blood
• Direct Microscopy
- Gram staining - gram-positive
oval budding yeast cells with
pseudohyphae

Culture
• SDA with antibiotic supplements at 37°C
• Grow in bacteriological culture media -blood agar
• Blood culture bottles (conventional and
automated blood)
• ™Colonies - creamy white, smooth, and pasty with
typical yeasty odor™

Tests for Species Identification
• ™Germ tube test: specific test for C. albicans
• Also called Reynolds Braude phenomenon
• „Germ tubes - long tube like projections extending
from the yeast cells
• „Differentiated from pseudohyphae as there is no
constriction at the origin

• ™Dalmau plate culture: Culture on cornmeal
agar C. albicans produces thick walled
chlamydospores
• ™CHROMagar: Different Candida species
produce different colored colonies

• ™Growth at 45°C:
- It differentiates C. albicans (grows) from C.ubliniensis
(does not grow at 45°C)
• ™Carbohydrate fermentation test
• Carbohydrate assimilation
• ™Molecular methods

Immunodiagnosis
• ™Antibody detection: ELISA, latex agglutination tests - antibodies
against cell wall mannan antigen
• ™Antigen detection: cell wall mannan and cytoplasmic antigens -
ELISA
• ™Enzyme detection: enolase, aspartate proteinase
• ™Test for metabolites: mannitol, arabinitol
• G test is done for detection of b-1-3 -D-glucan

Treatment
• Cutaneous candidiasis or oral thrush: topical azole
• ‰Esophageal and vulvovaginal candidiasis: oral fluconazole or
caspofungin
• ‰Disseminated candidiasis: liposomal amphotericin B or caspofungin
• C. glabrata and C. krusei exhibit intrinsic resistance to azoles

CRYPTOCOCCOSIS
• Cryptococcus neoformans
• Species and Serotypes
• Two species: C.neoformans and C. gattii and four serotypes A, B, C
and D.
• Two varieties—C. neoformans var. grubii and C. neoformans var.
neoformans

Pathogenesis
• Infection is acquired by inhalation of aerosolized forms of
Cryptococcus
• Immunocompetent individuals - defense mechanisms limit the
infection
• ™Low immunity - pulmonary infection dissemination through blood
• ™CNS spread: cross blood-brain barrier - migrate directly across the
endothelium or carried inside the acrophages as “Trojan horse”

Virulence factors
• Polysaccharide capsule
- Antiphagocytic and also inhibits the host’s local immune responses
• „Ability to make melanin by enzyme phenyl oxidase
• „Other enzymes – phospholipase and urease

Risk factors
• Patients with advanced HIV infection with CD4 T cell counts less than
200/μL
• „Patients with hematologic malignancies
• Transplant recipients
• „Patients on immunosuppressive or steroid therapy

• Pulmonary cryptococcosis: first and the most common presentation
• ™Cryptococcal meningitis: chronic meningitis, with headache, fever,
sensory and memory loss, cranial nerve paresis and loss of vision
(due to optic nerve involvement)
• ™Skin lesions
• Osteolytic bone lesions

Epidemiology
• Geographical distribution: C. neoformans var. grubii (serotype A)
strains are found worldwide
• C. neoformans var. neoformans (serotype D) strains are restricted to
Europe
• C. gattii is confined to tropics
• Habitat: C. neoformans – soils contaminated with avian excreta and
pigeon droppings.

• Specimens - CSF, blood or skin scrapings
• Direct Detection Methods
• ™Negative staining: Modified India ink stain
and nigrosin stain - demonstrate the
capsule
• Gram staining - gram-positive round
budding yeast cells

Cryptococcus
• Other stains:
- Mucicarmine stain: It stains the carminophilic cell wall of C.
neoformans
- Masson-Fontana stain: It demonstrates the production of melanin
- Alcian blue stain to demonstrate the capsule.
• Capsular ™Antigen detection: from CSF or serum by latex agglutination
test

Culture
• SDA without antibiotics, blood agar or chocolate agar
and incubated at 37°C
• Blood inoculated in biphasic blood culture bottles
• Colonies - mucoid creamy white and yeast like
• Confirmation of Cryptococcus species :
- Niger seed agar and bird seed agar
- Growth at 37°C
- Urease test is positive
- Assimilation of inositol and nitrate
- Mouse pathogenicity test

Treatment
• Without CNS involvement: Fluconazole
• HIV-infected patients with CNS involvement: induction phase for two
weeks (amphotericin B ― flucytosine) oral fluconazole therapy till
CD4 T cell count raises >200 /μL for 6 months

ZYGOMYCOSIS
• Life-threatening infections caused by aseptate fungi belonging to the phylum
Zygomycota
1. Order mucorales (causes mucormycosis)
„- Rhizopus (R. arrhizus and R. microsporus)
„- Mucor racemosus, Rhizomucor pusillus
„- Lichtheimia corymbifera
- Apophysomyces elegans.
2. Order entomophthorales (causes entomophthoromycosis)
„- Basidiobolus ranarum
„- Conidiobolus coronatus.

Mucormycosis
• Pathogenesis
• Spores found ubiquitously in the environment
• Transmission - inhalation, inoculation or rarely ingestion of spores
• Spores  mycelial form which are angioinvasive
• Predisposing factors:
- Conditions with increased iron load
- Diabetic ketoacidosis
- End stage renal disease
- Iron therapy or deferoxamine
- Defects in phagocytic functions

1. Rhinocerebral mucormycosis:
- Most common form, Orbital
cellulitis, proptosis and vision
loss
2. Pulmonary mucormycosis - in
patients with leukemia
3. Cutaneous mucormycosis
4. Gastrointestinal mucormycosis –
necrotizing enterocolitis
5. Disseminated mucormycosis:
Brain
6. Miscellaneous forms

• ™Histopathological
staining or methenamine
silver stain of tissue
biopsies shows broad
aseptate hyaline hyphae
with wide angle branching
™

• ™Culture on SDA at 25°C:
white cottony woolly
colonies with tube filling
growth (lid lifters)
• In some species (e.g.
Rhizopus) - salt and
pepper appearance

• LPCB mount colonies - broad
aseptate hyaline hyphae 
sporangiophore
sporangium containing
numerous sporangiospores
• Rhizoids - root like growth
arising from hyphae

Treatment
• Amphotericin B deoxycholate - drug of choice for all forms of
mucormycosis
• Alternatives - Posaconazole or isavuconazole

ASPERGILLOSIS
• Aspergillosis refers to the invasive and allergic diseasescaused by a
hyaline mold named Aspergillus. There are nearly 35 pathogenic and
allergenic species of Aspergillus, important ones being—A.
fumigatus, A. flavus and A. niger

Pathogenesis
- Widely distributed in nature - decaying plants
- Transmission – inhalation
• Risk factors for invasive aspergillosis are:
- Glucocorticoid use (the most important risk factor)
- Profound neutropenia
- Neutrophil dysfunction
- Underlying pneumonia, chronic obstructive pulmonary disease,
tuberculosis or sarcoidosis
- Anti-tumor necrosis factor therapy.

• Pulmonary aspergillosis: most common form
- Allergic bronchopulmonary aspergillosis (ABPA)
- Severe bronchial asthma
- Extrinsic allergic alveolitis
- Aspergilloma (fungal ball)
- Acute angioinvasive pulmonary aspergillosis
- Chronic cavitary pulmonary aspergillosis

Other forms of aspergillosis
• „Invasive sinusitis
- ••Chronic granulomatous sinusitis
- Maxillary fungal ball
- Allergic fungal sinusitis
• „Cardiac aspergillosis: Endocarditis (native or prosthetic) and
pericarditis
• „Cerebral aspergillosis: Brain abscess, hemorrhagic infarction, and
meningitis

Other forms of aspergillosis
• „Ocular aspergillosis: Keratitis and endophthalmitis
• „Ear infection: Otitis externa
• „Cutaneous aspergillosis
• „Nail bed infection: Onychomycosis
• „Mycotoxicosis

• Specimens - sputum and tissue biopsies
• Direct Examination
- KOH (10%) mount or histopathological staining of specimens
narrow septate hyaline hyphae with acute angle branching
• Culture: SDA and incubated at 25°C
- Species identification is done based on macroscopic and microscopic
(LPCB mount) appearance of the colonies

Colony morphology of common Aspergilli

Microscopy of common Aspergilli

Identification features of Aspergillus species
Aspergillus Macroscopic
appearance of colony
Microscopic appearance of colony (LPCB
mount)
A.fumigatus Colonies- Smoky green,
velvety to powdery,
reverse is white
Vesicle is conical-shaped.
Phialides are arranged in single row
Conidia arise from upper third of vesicle
Conidia are hyaline
A.flavus Colonies- Yellow green,
velvety,
reverse is white
Vesicle is globular shaped
Phialides in one or two rows
Conidia arise from entire vesicle
Conidia are hyaline
A.niger Colonies-
Black,
cottony type, reverse is
Vesicle is globular shaped
Phialides in two rows
Conidia arise from entire vesicleEssentials of Medical Microbiology

Other Tests
• Antigen Detection - ELISA - Aspergillus specific galactomannan
• Antibody Detection
- Useful for chronic invasive aspergillosis and aspergilloma, where the
culture is usually negative
- In allergic syndromes such as ABPA and severe asthma, specific
serum IgE levels are elevated.
• Detection of Metabolites
- b-1-3-D-glucan (by G test) or mannitol (by gas liquid chromatography)

Treatment Aspergillosis
• ‰Invasive aspergillosis—voriconazole
• ABPA—itraconazole
• ‰Single aspergilloma—surgery
• ‰Chronic pulmonary aspergillosis—itraconazole or voriconazole
• For prophylaxis - posaconazole

PENICILLIOSIS
• Clinical Significance
• Penicillium has more than 250 species, most are found as
saprophytes in the environment
• Penicillium marneffei
• Mycotoxicoses - toxins released by certain species of Penicillium such
as P. cyclopium, P. verrucosum and P.puberulum

PENICILLIOSIS
• Invasive penicilliosis: endophthalmitis and endocarditis
• „Superficial disease: otomycosis, keratitis and Onychomycosis
• Allergic disease: asthma and allergic pneumonitis

• P. marneffei - dimorphic fungus
• Other Penicillium - only as molds, grow easily on
SDA at 25°C
• ™Colonies - rapid growing, flat with velvety to
powdery texture and greenish in color

• LPCB mount of the colonies
- Hyaline thin septate 
conidiophore and its branches
 elongated metulae  flask-
shaped phialides originate
chain of conidia
- brush border appearance

Penicillium marneffei
• Penicillium marneffei - thermally dimorphic fungus
• Renamed as -Talaromyces marneffei
• causes opportunistic infection in HIV-infected patients. It
• Epidemiology
- Endemic in South East Asian countries including Thailand, Vietnam
and India (Manipur)

Pathogenesis
• Rural areas where the bamboo rats (reservoirs) are prevalent,
• No direct rat to man transmission
• Risk factors: Immunocompromised hosts
• Transmission - inhalation of conidia
• ™Mold to yeast conversion occurs in the lungs and then the yeast form
spreads via blood to reticuloendothelial system

• Systemic infection: fever, weight loss, dyspnea, lymphadenopathy
and hepatosplenomegaly
• Skin lesions: Warty lesions mimicking that of molluscum
contagiosum

• ™Histopathological staining of
tissue sections, skin scrapings or
blood smear
- Oval or elliptical yeast cells with
central septation,

• Culture: P. marneffei being
dimorphic
• Yeast like colonies at 37°C and
mold form at 25°C
• ™Mold form - brick red pigment

Treatment
• AIDS patients with severe penicilliosis - amphotericin B 
maintenance therapy with itraconazole for 12 weeks
• Mild penicilliosis: Itraconazole is recommended for 12 weeks

Pneumocystis Pneumonia
• Taxonomy
• Once thought to be a protozoan, now it is classified under fungus
based on nucleic acid sequence studies
• Renamed from P.carinii to Pneumocystis jirovecii

Pathogenesis
• Exists in cyst and trophozoite forms
• In human tissues both cysts and trophozoites are found.
• Cysts inhaled  carried to the lungs transform into the trophozoite
stage  induce an inflammatory response  recruitment of plasma
cells  frothy exudate filling the alveoli  plasma cell pneumonia

• Specimens: lung tissue or fluids obtained
by bronchoscopy, bronchial lavage, or
open lung biopsy
• Histopathological examination
• Gomori’s methenamine silver staining -
method of choice

• Cysts resemble black colored crushed ping-pong balls, against the
green background
• PCR assay
• Detection of 1, 3 β-D-glucan in serum
• Treatment:
- Cotrimoxazole - 14 days in non-HIV patients and 21 days in patients
with HIV
- Recommended drug for primary and secondary prophylaxis in
patients with HIV

Fusariosis
• Soil and plant saprophytes found worldwide rarely cause human
infections
• ™In immunocompetent individuals:
- Keratitis in contact lens wearers
- Onychomycosis.
• ™In immunocompromised patients - angioinvasive and cause
pulmonary and sinus infection
• ™Neutropenia and hematologic malignancies - disseminated fusariosis

Fusarium species (LPCB mount)

• ™Humans pathogens: F. solani (most common), followed by F.
oxysporum and F. verticillioides
• Colony: Rapid growing Cottony, flat, spreading white to pink colonies
• LPCB mount - hyaline septate hyphae bearing round microconidia,
sickle-shaped large macroconidia and chlamydospores
• Treatment
• Liposomal amphotericin B, voriconazole or posaconazole
• Resistant to many antifungal agents

MYCOTOXICOSES
• Mycotoxicosis: disease produced following consumption of food
contaminated by toxins liberated by certain fungi
• Mycetism: toxic effects produced by eating poisonous fleshy fungi;
usually different types of mushrooms

Features of common Mycotoxins
Mycotoxin Produced by
fungal species
Source Clinical condition
Aflatoxin Aspergillus
flavus
A.parasiticus,
A.nomius
Penicillium
puberulum
Nuts,
Maize
Hepatoma, Hepatitis
Indian childhood cirrhosis
Reye’s syndrome
Fumonisins Fusarium
moniliforme
Maize Equine
leukoencephalomalacia
Porcine pulmonary edema

fungal species
Trichothecenes Fusarium
graminearum
Maize,
wheat,
sorghum
Alimentary toxic aleukia
Biological warfare (yellow
rain)
Ochratoxin Aspergillus
ochraceus,
A.niger
Penicillium
verrucosum
Cereals,
bread
Nephropathies
(Balkan endemic
nephropathy)

fungal species
Cyclopiazonic
acid
Aspergillus
flavus,
A.versicolor,
A.oryzae
Penicillium
cyclopium
Groundn
ut, corn
Kodua poisoning
Co-contaminant with
aflatoxin
Zearalenones Fusarium
graminearum
Wheat,
maize
Genital disorder in pigs

Features of common mycetism
Mushroom
poisoning
Produced by
fungal species
Ergot alkaloid Claviceps
purpurea
Rye flour St. Anthony’s fire
Coprine
poisoning
Coprine
atrementarius
Butter Antabuse like reaction
Muscarine Inocybe fastigiata Food Cholinergic effect
Ibotenic acid,
muscimol
Amanita
pantherina
Edible
mushroom
Abdominal pain,
vomiting, diarrhea
Cyclopeptide Amanita Toadstools Hepatocellular failure,

Quick Assessment

MCQs
• All are yeast or yeast like fungi
except:
a. Candida
b. Trichosporon
c. Cryptococcus
d. Trichophyton
• Fungi which do not have sexual
stage:
a. Zygomycota
b. Ascomycota
c. Basidiomycota
d. Fungi imperfecti

MCQs
• Organism that does not affect nail:
a. Trichophyton
b. Epidermophyton
c. Microsporum
d. Candida albicans
• A patient coming from Himachal
Pradesh, presents with multiple
skin lesions. Microscopy reveals
cigar-shaped yeast cells and
asteroid bodies. Microscopy of
culture shows ‘flower like’ pattern.
Identify the agent?
a. Candida
b. Sporothrix schenckii
c. Epidermophyton
d. Rhizopus

MCQs
• Germ tube test is diagnostic
for:
a. Candida glabrata
b. Candida albicans
c. Cryptococcus
d. Coccidioides immitis
• Example for fungus having
branching, aseptate hyphae are
all except:
a. Rhizopus
b. Absidia
c. Penicillium
d. Mucor

MCQs
• Chromoblastomycosis is caused
by:
a. Epidermophyton
b. Histoplasma
c. Exophiala
d. Penicillium
• Which of the following
organism is not been isolated in
artificial culture media?
a. Cryptococcus neoformans
b. Rhinosporidium seeberi
c. Histoplasma capsulatum
d. Penicillium marneffei

MCQs
• Most common fungus causing
orbital cellulitis in a patient
with diabetic ketoacidosis is:
a. Mucor
b. Aspergillus
c. Candida
d. Cryptococcus
• Asteroid bodies is observed in:
a. Sporotrichosis
b. Histoplasmosis
c. Candidiasis
d. Chromoblastomycosis

MCQs
• Fluorescent dye used for
detection of fungi in tissue
specimen is:
a. Methenamine silver stain
b. Calcofluor white
c. Hematoxylin and Eosin staining
d. India ink
• 12. Which of the following is
added in Sabouraud’s Dextrose
Agar to suppress the growth of
contaminating (saprophytic)
fungi?
a. Cycloheximide
b. Chloramphenicol
c. Gentamicin
d. Amphotericin B

MCQs
• Tinea versicolor is caused by:
a. Candida albicans
b. Trichophyton rubrum
c. Trichophyton violaceum
d. Malassezia furfur
• 14. Broad-based budding is
seen in:
a. Histoplasma
b. Blastomyces
c. Cryptococcus
d. Penicillium

MCQs
• Aflatoxin is produced by:
a. Aspergillus flavus
b. Histoplasma
c. Sporothrix schenckii
d. Penicillium marneffei
• Spherules are seen in:
a. Chromoblastomycosis
b. Rhinosporidiosis
c. Mucormycosis
d. Aspergillosis

MCQs
• Barrel-shaped arthroconidia are
seen in:
a. Histoplasmosis
b. Cryptococcosis
c. Coccidioidomycosis
d. Paracoccidioidomycosis
• 18. Sclerotic bodies are seen in:
a. Mucormycosis
b. Aspergillosis
c. Rhinosporidiosis
d. Chromoblastomycosis

MCQs
• Spaghetti and meatball
appearance is seen in:
a. Hortaea werneckii
b. Trichosporon beigelii
c. Piedraia hortae
d. Malassezia furfur
• 20. The drug of choice for
Pneumocystis pneumonia is:
a. Amphotericin B
b. Flucytosine
c. Cotrimoxazole
d. Voriconazole

MCQs
• Sickle-shaped large
macroconidia is seen in:
a. Microsporum
b. Epidermophyton
c. Fusarium species
d. Pneumocystis jirovecii
• The cysts resemble crushed
ping-pong balls is seen with:
a. Microsporum
b. Pneumocystis jirovecii
c. Epidermophyton
d. Fusarium species

MCQs
• Azole active against
mucormycosis is:
a. Voriconazole
b. Fluconazole
c. Itraconazole
d. Posaconazole
• 24. Candida species resistant to
azoles is:
a. C. albicans
b. C. krusei
c. C. tropicalis
d. C. dubliniensis

Thank you...!

Oerview Of Mycology

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