MYCOLOGY
Margie Morgan, PhD D(ABMM)
Just the basics – meant for board review or brief study of this fascinating area of microbiology!
Mycology
Starting point
Yeast are:• Unicellular / produce budding daughter cells• Colony on solid media are usually white to beige and
appear much like bacterial colonies• Some genera produce mucoid colonies
(Cryptococcus)
Starting point
Molds are:• Filamentous with hyphae• Produce conidia [spores]• Colonies on solid agar are downy, fluffy, cottony• Most mold colonies are pigmented which aid in
identification
hyphaespores
Appropriate Specimens and Transport conditions for Fungal disease diagnosis• Fungi are very hardy organisms • No requirement for special transport media for culture
submission• Sterile containers used to prevent bacterial contamination• Numerous sites are appropriate for culture• Respiratory specimens – sputum, bronchial lavage,
brushings, nasal sinuses• Tissue biopsies• Cutaneous - Skin scrapings, material from lesions• Ocular• Sterile body fluids including CSF• Blood, bone marrow
Fungal Culture Media• Sabouraud’s glucose agar (SABS)
All purpose Fungal media – nothing to discourage bacteria to grow
SABS best used for the subculture of fungi for workup
Contains 2% glucose, pH @7.0
• Inhibitory mold agar Selective SABS agar with chloramphenicol, gentamicin [inhibit bacterial growth] and enrichment,
Good for the primary recovery of dimorphic pathogenic fungi. Saprophytic fungi and dermatophytes inhibited
on inhibitory mold agar
Common Fungal Media• Mycosel/Mycobiotic agars
• Selective SABS with chloramphenicol and cycloheximide • Used for culture of dermatophytes – fungi that cause skin, hair and nail
infections• Brain heart infusion agar
• Primary recovery of all fungal organisms• Can make it more selective by adding chloramphenicol and
cycloheximide• Can add blood to agar to nurture systemic fungi
• Fungal cultures incubated for 4 weeks at 30˚C , room air• Lower temperature than bacterial culture incubation [35˚C]• If plates are used for fungal cultures the plates must be sealed with
air permeable tape for laboratory safety
What effect does Cycloheximide have when added to media?• Prevents rapidly growing molds from overgrowing dimorphics and dermatophytes• This is the positive aspect of cycloheximide in media
• Beware: it is not all good, it can suppress important fungi from growing. Inhibited fungi include:• Trichosporon beigelii• Candida tropicalis• Cryptococcus neoformans• Yeast phase of Blastomyces• Yeast phase of Histoplasma
Inoculate fungal media
Seal plates with tape to prevent culture contamination and escape of fungal spores
Incubate at 30˚C for 4 wk
If growth occurs - perform proper identification methods:
Yeast identification methods Manual and automated biochemical reactions capable of identifying most yeast species.
Newer methods [Mass spectrometry – MALDI-TOF and 16 sRNA sequencing
Processing of Fungal Cultures - stepwise
Lactophenol cotton blue [LCB] adhesive tape preparation is method used for mold identification.
LCB mounting medium consists of phenollactic acid, glycerol and aniline cotton blue dye.
Clear adhesive (scotch) tape touches a mold colony, picking up fungal hyphae and pressed into one drop of LCBon a microscope slide.
If LCB prep is not able to identify a mold 16sRNAsequencing can be usedto identify problematic molds in reference laboratories.
Mold Identification methods
Safety in the Mycology Laboratory• If a culture is growing a mold, it cannot be opened on the
bench top• All mold work must be performed in a BSL-2 biosafety
cabinet with Hepa filtration• Yeast identification can be performed on the bench top
Direct Exams used to identify fungi directly from patient specimens• Gram stain – all specimen types can be Gram stained.
Can only reliably detect yeast by Gram stain.
• KOH preparation – Skin, Hair or Nails examined for both yeast and/or hyphae
• Calcofluor white stain – all specimen types can be stained and examined for yeast and/or hyphae
• India ink – Primarily used for CSF for the detection of Cryptococcus neoformans and C. gattii
Yeast cells stain blue [Gram positive]. Examine for budding cells to confirm that it is a yeast cell and not an artifact. Examination on oil immersion lens.You can also detect pseudohyphae on Gram stain. Mold can be difficult to identify on a Gram stain.
pseudohyphae
moldpseudohyphae
Gram Stain
Used to detect yeast and/or hyphae in skin, hair and nail specimens using 40X light microscope.KOH dissolves keratin found in cell materialand frees hyphae from the cellKOH exams can be difficult to interpret!
KOH – potassium hydroxide prep
Yeast, pseudohyphae, and mycelial fungi bind with the Calcofluor white stain. Prep is interpreted using a fluorescence microscope.Sensitivity and specificity is improved over the KOH preparation.
Calcofluor white stain
One drop of black ink is placed into one drop of CSF and examined using a 40X lens on light microscope
It is a “negative” stain, staining the background not the yeast cellThe clearing is thepolysaccharide capsule ofCryptococcus neoformans or C. gattii. Specificity is improved if you look for budding yeast cells.
India Ink
Methenamine Silver Stain [GMS] – yeast and hyphae stain grey to black.
Examine the hyphae for presence of septations in the hyphae, broad or more narrow width and angle of branching.Examine the size and budding pattern of observed yeast.We will observe on later slides how these criteria can assist in identification.
Examination of fungi in fixed tissue
PAS-positive staining red against a green or blue background
Periodic Acid Schiff [PAS]
Stain-Cryptococcus neoformans polysaccharide capsule stains pink
Mucicarmine [Mucin] stain
Great for cellularity, but GMS, or PAS better show features of the fungi.
Hematoxylin and Eosin Stain
DIMORPHIC FUNGIImportant systemic pathogens with some unique characteristics
What does Dimorphic mean?
• Two forms exist for one fungus species depending on temperature and conditions of environment• Mycelial form - Hyphae and conidia
• free living form found in nature and at laboratory temperature <=30˚C• Yeast or yeast like form
• parasitic phase found in human tissue or in the lab >= 35˚
Histoplasma capsulatum – moldfrom 30˚C culture
Histoplasma capsulatum – yeastfrom tissue and 35˚C culture
Dimorphic Fungi capable of causing systemic infection – most common
• Histoplasma capsulatum• Blastomyces dermatitidis• Coccidioides immitis• Paracoccidioides brasiliensis• Sporothrix schenckii• Penicillium marneffei
Histoplasma capsulatum• World wide distribution / In USA in Ohio, Missouri, and Mississippi River valleys considered endemic
• Associate with Bat guano (Spelunker = cave explorers) and bird droppings
Histoplasmosis Disease• 95% of infections are subclinical• 5% infections:
• Progressive pulmonary• Chronic systemic infection with dissemination to the RES
system including bone marrow• Acute fulminating systemic disease (fatal)
• Reactivation disease can occur in elderly and immunosuppressed (AIDS is a good example)
• Bone marrow exam is useful in diagnosing disseminated infections
• Mucocutaneous lesions are a unique & common site of dissemination
The yeast of Histoplasma capsulatum prefer to be intracellular and inhabit
Macrophages.Small 2 – 4 um, regular in size, and oval to round.
Do not have a capsule, this is just a staining artifact.
H & E PAS
Gram Wright’s
Histoplasma will stain with a variety of stains
Histoplasmosis rapid diagnosis
• Antigen detection in urine• Quantitative Enzyme immunoassay• Random urine specimen• Most useful for disseminated infection and chronic
pulmonary disease• Antigen is detectable in >=85% of these infections• Good for diagnosis of immune suppressed patients
that do not produce a detectable antibody response• Antibody tests are available but have been replaced
mostly by Antigen detection
Histoplasma capsulatum• Fungal culture incubated at 30˚C
• Very SLOW growing taking 2 – 8 weeks to form colonies• Colony is white to brown and cottony • Microscopic appearance – tuberculated macroconidia that are
large and round (8 – 16 µM) plus small microconidia (2 - 4µM) [see picture]
• Microconidia are the infectious particle growing in nature and capable of penetrating deep into the lung
• DNA probe must be used to confirm identification so there is no confusion with look alike fungi to the inexperience
• Sepedonium species looks somewhat like Histoplasma and is considered a look a like fungus – it is a contaminate
Histoplasma capsulatum culture at 30˚C is white and cottony.
Microscopic exam: Tuberculate [projections]on the macroconidia.Microconidia are the infectious particle. Thin hyaline septate hyphae
Appearance in culture at 30 degrees C
Sepedonium species
Appearance in culture at35 degrees C
• Culture at 35˚C is yeast phase• Grow as small yeast, round to oval, always consistent
in size and shape (2 -4 uM) narrow neck at the budding juncture
Histoplasma capsulatum in tissue• Granulomas are usually produced and can be either
caseating or non caseating• Infection usually begins by breathing in the microconidia
and infecting the Lung• Infection disseminates to organs of the
Reticuloendothelial System (RES) – with high % of dissemination to the Bone Marrow
• Intracellular budding yeast (2 – 4 µM) are seen in all tissues
Leishmania speciesNote small round kinetoplast next to nucleus
Toxoplasma
Histoplasma capsulatum
Beware of look alike organisms in tissue specimens!!
H capsulatum var duboisii yeast cells are 8 – 10 uM in size, which is 2X the size of regular Histoplasma capsulatum yeast cells.
H. capsulatum var duboisii disease is found in Central AfricaCauses infection in skin and boneThe 30˚C culture is identical to H capsulatum.
Unusual variant of H. capsulatum
Blastomyces dermatitidis• Epidemiology
• Ohio and Mississippi River valleys• No association with specific animal or activity• Forrest and river banks?• Primarily a pulmonary infection which may disseminate to the skin
and bone
Well demarcated skin lesion is typicalScraping of skin lesions are full of yeast cells
Blastomyces dermatitidis• Culture at 30˚C
• Grows in 2- 3 weeks• Fluffy white – buff colored mold, prickly• Pear shaped conidia at the end of supporting hyphae
– looks like lollipops• Look alike fungus – Chrysosporium species• Do DNA probe test to confirm identification
BlastomycesChrysosporium
Slow growing yeast colony taking @ 4 weeks to form a colonyYeast cell is 8 – 20 um in size and is unique for it’s Broad Based Budding pattern and the double contoured wall.
Blastomyces culture at 37 degrees C
Blastomyces dermatitidis histopathologyMixed pyogenic and granulomatous inflammation is observed in tissue with Broad based budding yeast cells
Coccidioides immitis
• Endemic in SW USA, Mexico, South America, in areas known
as the Sonoran life zone with a warm climate and desert sandsInfection is from inhalation of fungal particles found in the sand
• Coccidioides posadasii is a genetically related to C. immitis. The two species are located in different endemic regions, but produce the same disease process
Coccidioidomycosis• 95% of infections are asymptomatic or with limited
symptoms • The remaining 5% are focal pulmonary, progressive
pulmonary or disseminated infections. Dissemination to the central nervous system is difficult to cure and has a high fatality rate.
• Higher incidence of dissemination occurs in patients with: • defects in cell mediated immunity (HIV), • darker skinned ethnic groups, • pregnancy
Coccidioides immitis [posadasii]
• Culture at 30˚C• Requires only 2 – 3 days to grow, colony starts waxy and
becomes wooly in around 7 – 10 days• Under the microscope one looks for foci of septated hyphae
with thick walled barrel shaped arthroconidia with clear spaces in between. The clear spaces are dead arthroconidia.
• Arthroconidia infectious particle in nature• Very infectious to laboratory personnel
Coccidioides • Malbranchea species can look like C. immitis under the
microscope• Because of look-a-like fungi one needs to confirm
identification of Coccidioides immitis with DNA probe or similar method to be sure!
Coccidioides Malbranchea
Barrel shaped alternating arthroconidia are produced in cultures grown at both 30 and 35 C.There is no yeast phase for C. immitis [posadasii]
No yeast phase with Coccidioides!
Coccidioides Histopathology• Thick walled spherules (10 – 80 uM) with endospores
are seen in tissue. This is the second form of Cocci. No yeast cells are produced in tissue for this fungus.
• Spherules are at all stages of development- fragmented spherules to well formed with endospores
• Granulomatous inflammation with caseation is usually observed
Development of Cocci spherules from the inhalation of Arthroconidia from nature
Rhinosporidium seeberi (aquatic parasite) forms spherules but much larger than the Cocci spherules - they are usually > 80 uM in size. Also R. seeberi almost always cause oral or nasal mass lesions
Oral or nasal mass lesionsof Rhinosporidium seeberi
Coccidioidesspherules
Coccidioides is not the only spherule forming organism!
Paracoccidioides brasiliensis
• South American Blastomycosis – endemic area Brazil, Venezuela, Columbia
• Inhale infectious particle from soil• >95% of infections in males, possibly due to
estrogen inhibition of mycelial to yeast transformation
• Disease presentation:1. Pneumonia2. Disseminated infection to 2 or more organs3. Extrapulmonary lesions on the face and oral
mucosa
Paracoccidioides
• Cultures at 30*C for mycelial phase are usually not done due to slow growth and nonspecific sporulation
• Culture @ 37˚C• Slow growing yeast• Large yeast (10 – 30uM) with multiple daughter buds (2 – 10
uM) in size • Unique yeast cell known as the Mariner’s wheel or Pilot’s wheel
yeast
Tissue Exam ofParacoccidioides brasiliensis
If more than 2 buds off mother cell – High likelihood it is ParacoccidioidesGranulomatous inflammation with GiantCells
Sporotrichosis
• Sporothrix schenckii• Cutaneous inoculation of fungus from penetrating injury with a
spore or thorn (rose bush)• Initial skin lesion w/wo ulceration• Lymph-cutaneous spread – bone – systemic• Pulmonary and CNS infections are rare but reported
Starts as one ulcerative lesion and then chainsUp the lymphatics – can involve lymph nodes and bone
Sporothrix schenckii•MOLD PHASE
• 30*˚C growth in 3 -5 days• Turns brown to black over time• Septate hyphae with conidia in daisy wheel pattern
•YEAST PHASE• At 37˚C small oval yeast cells, elongated 2 – 5 µM, described as cigar bodies
Sporothrix schenckii• Histology –
• Pyogenic – to – granulomatous inflammation• Hard to find yeast in human tissue• Asteroid body known as Splendore-Hoeppli phenomenon
can be seen, but not specific to Sporothrix, also seen in:• Zygomycetes (Mucorales)• Aspergillus• Blastomycosis• Candida
Daisy like spore arrangement
Sporothrix schenckii
Green colony with red diffusable pigment Uncommon dimorphic fungus The only species of Penicillium that is dimorphicCauses skin lesions in tropics and Pneumonia in immune suppressed
Penicillium marneffei
Penicillium marneffei yeast like cells in tissue
SUBCUTANEOUS FUNGAL INFECTIONSVery unique structures in tissue!
Subcutaneous Fungal Infections Most common will be described• Mycetoma [2 types]
• Actinomycotic – caused by higher bacteria• Eumycotic – caused by dark pigmented molds
• Chromomycosis [Chromoblastomycosis]• Phaeohyphomycosis• Sporotrichosis
Mycetoma• First observed in India and known as Madura Foot or Maduromycosis • Found in the hot temperate parts of the
world
• Three criteria describe Mycetoma:1. Lesions lead to swollen extremities2. Draining sinuses3. Sulfur granules observed in tissue and found in the
weeping drainage
• Fungus grows on organic debris in soil• Implanted into subcutaneous tissue from trauma
Swollen extremity and draining sinus with sulfur granules
Sulfur Granule
Mycetoma
Mycetoma • There are two types of Mycetoma:
1. Actinomycotic mycetoma – caused by higher bacteria species
2. Eumycotic mycetoma – caused by the black molds
• Actinomycotic Mycetoma• 98% of cases of Mycetoma• Nocardia species most common cause• Sulfur granules formed in tissue and the granules vary in
color and contain a matrix of the filamentous bacteria
Gram stain as filamentous Gram positive bacilli – can be poorly staining and appear speckled.Nocardia are positive [red] on the Modified Kinyoun stain.
Modified acid-fast stain[modified Kinyoun stain]
Gram stain of sputum containing Nocardia
Nocardia
Edge of granule has thin filamentous bacteriafor both bacteria – Nocardia is modified acid fast [PAF] positive and is aerobic bacteria. Actinomyces is PAF negative and grows anaerobically.
Beware! Sulfur granule caused by Actinomyces israelii looks identical.
Actinomycotic sulfur granule - Nocardia
Requires 3 – 5 days to grow on agar media [Sabs, 5% Sheep’s blood agar
Colony is dry and crumblyMusty smell
Total of 85 speciesNocardia asteroides is the most common species isolated from human infection
Identification by HPLCor molecular methods
Nocardia species cause mycetoma, and can also cause Pulmonary and Brain infections
Eumycotic mycetoma – subcutaneous infection caused by the black molds
Numerous species of pigmented/black fungi found naturally in the soil can cause this type of infectionCause @ 2% of cases of mycetoma Traumatic implantation injects the mold into the subcutaneous tissueMost common species of black mold include:
Cladophialophora (Cladosporium) carrioniiCladophialophora bantianaPhialophora verrucosaFonsecaea pedrosoiExophiala speciesWangiella species
Eumycotic sulfur granule – the granule is full of a matrix of thick fungal hyphae
Chromomycosis/Chromoblastomycosis
• Three characteristics describe Chromomycosis• Wart like lesions in subcutaneous tissue• Sclerotic bodies observed in tissue• Growth of dark/pigmented fungi
• Black mold naturally found in the soil cause infection through abrasion/ implantation
• Black molds that can cause Chromomycosis:• Cladophialophora [Cladosporium] carrionii• C. bantiana• Phialophora verrucosa• Fonsecaea pedrosoi• Exophiala species• Wangiella species
Chromomycosis/Chromoblastomycosis
Wart like/Verrucous lesionsIn subcutaneous tissue
Sclerotic Body/Medlar Body/Copper Penny is the uniquestructure found in tissue
Prototheca wickerhamii – the cause of Protothecosis• Algae without chlorophyll• Causes skin lesions & nodules• Most common in patients with suppressed immune
system• Compare morula of Protothecosis to sclerotic body of
Chromomycoses
Phaeohyphomycosis This infection is caused by traumatic implantation of dark
fungi into subcutaneous tissue• Variety of infections but nodules/lesions most common
with/without dissemination• Dark hyphae only observed in tissue
Black molds/Dark molds also known as Dematiaceous fungi Black colored colonies and the reverse [back of colony] is also blackNaturally brown hyphae and sporesOne of the major causes of mold growth due to water damage!
Black Molds – Dematiaceous fungi• Black colonies• Brown hyphae and spores• Numerous species • Difficult to identify
• All have one of four types of sporulation• Rhinocladiella-like• Cladosporium-like• Phialophora-like• Acrotheca-like
Rhinocladiella type sporulation
Phialophora type sporulation
Cladophialophora [Cladosporium type sporulation]
Acrotheca type sporulation
Exophiala species
Black Molds that can cause Mycetoma/Chromomycosis/PhaeohyphomycosisThese are difficult to identify but viewing is necessary!
Cladophialophora bantiana
Wangiella dermatitidis
Phialophora verrucosa
AlternariaOther black molds of importance:
Bipolaris australiensis
Very invasive fungal infection:Skin, nasalsinuses, bonebrain
Curvularia lunata
Center cell is the largest
Opportunistic fungal pathogenReported in patients with Bone Marrow Transplantation and Aplastic anemiaCan cause unusual erythematous skin lesions
Exserohilum rostrum• Associated with compounded pharmaceutical [steroid]
products contaminated with dust/dirt• Used for infections into lumbar spine and knee joints for
pain management• Meningitis• Spinal abscess• Synovial infections
Scedosporium apiospermum/Pseudallescheria boydiiCat fur-like colony
IMPORTANT YEAST CAUSING HUMAN INFECTION
Candida speciesCryptococcus neoformans & Cryptococcus gattii
Cutaneous and Superficial Mycoses
• Candida species (@ 10 found in humans)• Opportunistic pathogen involving skin or mucous
membranes from excessive exposure to moisture, antibiotics, or immune suppression
• Yeast is from endogenous source – found as normal flora in the GI and GU tracts and skin
• Variety of infections including: Thrush, vaginitis, skin lesions, nail, diaper rash, to more serious infections like fungemia and endoarditis.
Candida species
• Candida albicans – most common species causing @ 60% of human yeast infections
• Candida glabrata, C. krusei, and C. tropicalis are becoming more common in infection
• These 3 species are more likelyto be resistant to Fluconazole
• Candida parapsilosis has emerged as a pathogen of children and IV lines
Candida species
• Grow in 24 – 48 hours• SABS, IMA, BAP
• Bacteria-like colony – pasty white• Budding yeast – oval @ 7-8 um in size
form pseudohyphae (Yeast do not detach and form elongated hyhae) Can appear like sausage links
• Exception **Candida glabrata is @ 4 µM in size and does NOT form any pseudohyphae
Candida albicansIdentification
• Germ tube formation• Incubate small amount of yeast in serum for 3-4hr at 35 ˚C• Do not incubate >4 hr – this can lead to a false positive
reaction with C. tropicalis• C. dubliniensis also positive (uncommon yeast isolate)
• Chlamydospore formation• Growth on cornmeal agar >48 hrs• Rudimentary structures
C. albicanschlamydospore
C. glabrata only forms yeastNo pseudohyphae
ChromAgar for the identification of Candida
Chromogenic substratesTurn different colors with4 different yeast species
Yeast with pseudohyphae
Candida Histopathology• Pyogenic to granulomatous• Usually observe yeast cells, pseudohyphae and/or hyphae
appearing structures• Candida glabrata = smaller yeast cells and no pseudohyphae
GMS stain of Candida glabrataCandida species not glabrata
Cryptococcus neoformans
• In nature forms a 2um non-encapsulated yeast cell. It is associated with bird droppings (esp. pigeon). C neoformans is enriched by the nitrogen in the droppings.
• Yeast cells are inhaled – travels through the pulmonary system with hematogenous spread to brain and meninges
• Has tropism to the meninges• Infects mostly compromised hosts - AIDS
Cryptococcus neoformans
• Irregular sized (2 – 20uM) yeast cells• Polysaccharide capsule is virulence factor and it’s presence is used in
diagnostic tests for C. neoformans • India ink exam of CSF is a negative staining method/capsule not
stained, • Sensitive test for AIDS patients (90% sensitive)
• Cryptococcal antigen test – capsular polysaccharide is detected in both CSF and serum,• Test for diagnosis and can also follow recovery with falling titer /more
sensitive than India ink• Grows on mycologic agars but is sensitive to cycloheximide –
• Mucoid colonies due to capsule polysaccharide formation• Urease enzyme + Inositol assimilation +• Brown colonies produced on bird seed agar
Cryptococcus gattii – a closely related relative of C. neoformans• Isolated from forested area of the Pacific Northwest (British Columbia, Washington, Oregon and California) found in soil debris and tree species• Infection of normal and immune suppressed hosts• Mostly Pulmonary disease [Cryptococcoma] but can develop meningitis like C. neoformans• Culture and staining identical to C. neoformans except for L Canavanine glycine bromthymol blue medium –
C. gatti = blue
C. neoformans = colorless
Positive India Ink
Urea medium demonstrating urease enzyme activity of Cryptococcus
Observe Budding cells
Variability in size
Positive
Mucoid colonies ofC. neoformans andC. gattii
C. neoformans/C. gattii formsbrown colonies on Birdseed agar
Mucicarmine stain
Stains the capsular polysaccharide of capsule
Pneumocystis jiroveci could be confused with C. neoformans – Careful! Central nuclear staining
C. neoformans/ C. gattii
CUTANEOUS AND SUPERFICIAL MYCOSESMalassezia furfurDermatophytes
Malassezia furfur
• Pityriasis versicolor• Most superficial of the dermatomycoses • Found as normal flora on the skin,• More common on oily skin or high use of skin oils• Diseases: • Skin: macules, papules, patches, plaques on chest back and shoulders with either hypo or hyper pigmentation – does not invade into deeper tissues
• Fungemia in neonates caused by skin flora tunneling in the IV lipid feeding lines
Malassezia furfur• Lipophilic yeast – oil required for growth
• Media used for culture must contain oil or have oil overlay
• Small budding yeast 2 – 4 µM with collarette
Spaghetti and meatballs
Size range for Yeast• Candida glabrata/Histoplasma capsulatum
• 2 – 4 um• Candida species
• 8 – 10 um plus pseudohyphae• Cryptococcus neoformans/gattii
• 2 – 20 um• Blastomyces dermatitidis
• 8-15 um
Dermatophytes – Ringworm infections
• Hair, skin and nail infections• 3 genera of fungi
• Microsporum species (many)• Epidermophyton floccosum• Trichophyton species (many)
• Disease described by area of the body infected: tinea capitis (head), t. pedis (foot)
• Usually a clinical diagnosis not requiring culture• Can do a KOH prep or Calcofluor white prep to visualize fungal hyphae
Positive KOH prepShowing thin septate fungal hyphae
Calcofluor white stain with fluorescence – thin fungal hyphae
Microsporum canisMain cause of ringworm from dog and catWhite colony/ yellow on backside of colonyTuberculate macroconidia [spiny projections]Few if any microconidia
Microsporum gypseum infection from exposure to contaminated soil
Trichophytonrubrum
White colony with red diffusable pigment
Pencil shapedMacroconidiaMany micro-Conidia
Infection from fomites
Red diffusible pigment
Trichophytontonsurans
Ballooning Microconidia
Primary cause of epidemic scalp ringworm in children from infection of Hair
Epidermophyton floccosum
Beaver tail large spores without microconidiaKhaki green colony
Opportunistic Fungal PathogensInfections in the immune suppressed host
or special circumstancesHyaline moldsBlack molds
Opportunistic Fungi - hyaline
• Hyaline – no color to the hyphae• Regular septations in the hyphae • Branching – angle can be helpful in identification• Usually grow in 3 – 5 days at 30˚C• ??? of species thousands– taxonomy changing daily
Aspergillus species• Hyaline with septations• Numerous round conidia• In tissue - Branching at 45 degree angle• Primarily pulmonary infection in immune suppressed• Invade vessels, cause thrombosis & infarctions
Aspergillus Structure
Aspergillus speciesFour species most common in human infections:1. Aspergillus fumigatus 2. Aspergillus flavus3. Aspergillus niger4. Aspergillus terreus – unique and important – only
Aspergillus species resistant to Amphotericin B
Aspergillus Galactomannan Enzyme immunoassay – detects circulating Aspergillus antigen in the blood and/or bronchial lavage fluid
Problems with low sensitivity and specificity False positive reaction in patients on therapy with Piperacillin/Tazobactam, infected with Histoplasma capsulatum
Aspergillus fumigatus
Blue/Green colonyPhialids with spores areDirected upward
Aspergillus flavus
Green colonyOrange colored spores that surround the vesecle
Aspergillus niger
Black colonyBlack spores surround the vesicle
Aspergillus terreus Sandy colored colony
Aleurioconidia
Resistance to Amphotericin B
Aspergillus•fruiting head dichotomous•branching septate hyphae• branching at 45* angle
Pseudallescheria boydiican be confused for Aspergillus, hyphae is a bit thinner. Culture separates the two fungi.
Fusarium species – Common in nature/plantsdisease related to immune status of hostInfections reported: Disseminated in bone marrow
transplantsCorneal infections in contact
lens wearers
Scopulariopsis species –Soil and plantsInfections: Nail, skin, sinusitis, pulmonary and disseminated
Paecilomyces speciesIsolated from soil and foodOpportunistic pathogen in the immune suppressed
Penicillium species – most common mold in the environment, bread mold, uncommon cause of human disease
MUCORMYCOSIS/ZYGOMYCOSISHyalineBroad non-septate hyphae
Mucormycosis/Zygomycosis• Infections in diabetics, the elevated glucose enriches fungal growth – classic infection is rhinocerebral mucormycosis
• Sinus and pulmonary infection in the immune suppressed host
• Broad, hyaline, aseptate hyphae produced• Cultures grow in 24 hrs, coarse aerial hyphae• Can be difficult to culture – tube like hyphae killed during manipulation and plating
• Should not grind tissue• Mince tissue and place on agar
Zygomycete – coarse, aerial hyphae after 24 hours growth on SABS agar at 30˚C
Rhizopus Absidia
Distant rhizoids
Mucor
No rhizoids
Rhizoids
90˚ angle branching, aseptate, ribbon like
Invades vessels and can cause infarcts and thrombi
Zygomycetes (Mucorales)