Mycology and Parasitology Morphology

Malassezia furfur; Yeast

Causes tinea versicolor

• Requires lipid source

(sterile olive oil)

• Yeast with "spaghetti and

meatballs" morphology

Trichophyton rubrum (dermatophyte)

Skin and nail infections

(most common worldwide)

• Colony surface is

white/buff

• Colony bottom is red

(rubrum)

• Tear shaped microconidia

"birds on a wire"

• Negative for hair shaft

penetration

Trichophyton mentagrophytes (dermatophyte)

Looks very similar to T.

rubrum

• Positive for hair perforation

Microsporum canis (dermatophyte)

• Skin and scalp infections

usually from pets

• Colony surface is white

with yellow edges

• Spindly, rough

macroconidia with >6

cells

Microsporum gypseum (dermatophyte)

• Scalp and skin infections,

common in animals

• Oval, rough walled

macroconidia with <6 cells

Epidermophyton floccosum (dermatophyte)

• Skin and nail infections

• Colony is yellow, olive-gray,

or khaki

• Reverse of colony is orange-

brown

• Smooth club shaped

macroconidia with rounded

ends, often found in

clusters

o 2-6 cells

• No microconidia

Histoplasma capsulatum

• Small, narrow yeast in tissues

(easy to confuse with other

pathogens)

• Septate, hyaline hyphae with

spiny macroconidia

Blastomyces dermatitidis

• Broad based budding yeast (BBB)

often with double contours

• Mold form is not very distinct

Coccidioides immitis

Spherule form at 37 C

• Mold form

o Hyaline, septate with "Train

track" arthroconidia

Paracoccidioides brasiliensis

Yeast: large, round "mariner's

wheel" with circumferential

budding

o Don't mix this up with H.

capsulatum's mold form

macroconidia

• Mold: septate, hyaline,

terminal and intercalary

chlamydospores

Sporothrix schenckii

• Causes "rose gardener's disease"

• Yeast: cigar shaped, narrow based

• Mold: hyaline, septate hyphae with

"rosettes" of microconidia

Aspergillus fumigatus

• Blue-green colonies

o White apron and reverse

• Single row of phialides

covering top 2/3 of vesicle

Aspergillus flavus

• Yellow-green or olive colonies

o Light reverse side

• Circumferential phialides

Aspergillus niger

• Dark brown/black colonies

o Light reverse side

• Vesicle has two rows of

phialides covering the whole

surface

• Black conidia

Fusarium spp.

• Violet colonies

• "Canoe" or "banana"

microconidia

Acremonium spp.

• Gray, white, or pink

colonies

• Long, narrow,

unbranched phialides

with clusters of

microconidia

Penicillium spp.

• Usually a

contaminant, but can

cause infections

• Blue-green powdery

colonies with white

border

• "Skeleton hand"

phialide and conidia

arrangements

Scorpulariopsis spp.

• Contaminants but can cause

infection

• Powdery brown/tan colonies

• Rough "lemon drop" conidia

Rhizopus spp.

• Rhizoids and

unbranched

sporangiophores

• Sporangiophore = sac of

spores

Mucor spp.

No rhizoids

• Sporangia fall apart

easily

Alternaria (dematiaceous mold)

• Brownish black colonies

• Chains of club-shped conidia

with transverse and longitudinal

separations

Coccidia

• Stool samples

• Modified acid fast

Trypanosoma brucei

• Larger organism

• S- or C-shaped

• Small posterior kinetoplast

Trypanosoma cruzi

• Smaller

• C-shaped

• Large posterior

kinetoplast

Ted cruz

Plasmodium vivax

• Retics infected (large RBCs)

• Ring forms >1/3 size of RBC

• Mature troph is ameboid, fills RBC

• Schizont has 12-24 merozoites

• Gametocytes are large and oval

• Schuffner's dots

Plasmodium ovale

• Retics infected (large RBCs)

• Ring forms >1/3 size of RBC

• Mature troph more compact than P. vivax "

o "Comet forms"

• Schizont has 6-14 merozoites

• Gametocytes are large and oval

• Schuffner's dots

Plasmodium malariae

• Infects senescent RBCs (small to

normal)

• Ring form 1/3 size of RBC, thick

o Bird's eye

• Mature trophs = band and basket

forms

o Do not fill RBC

o Prominent pigment

• Schizont has 6-12 merozoites

o Rosette forms

• Gametocyte can fill RBC

Plasmodium falciparum

Only ring forms and gametocytes seen

in blood

• Infects all sizes of RBC

• Small, delicate ring forms

o Applique forms

o Multiple infections

o Multiple chromatin dots

• Gametocyte = banana shaped

Entamoeba histolytica

• Cyst (left)

o Up to 4 nuclei

o Chromatoidal body with

smooth ends

• Trophozoite (right)

o 15-20 microns

o Small, central karyosome

and fine peripheral

chromatin

o May see

erythrophagocytosis

(diagnostic)

Entamoeba coli

• Cyst (left)

o Up to 8 nuclei

• Trophozoite (right)

o 20-25 microns

o Eccentric karyosome

o Clumpy peripheral

chromatin

Entamoeba hartmanni

• Cyst (left)

o Looks like

aminiature E.hist

olytica

o Up to 4 nuclei

• Trophozoite (right)

o 5-10 microns

o Looks like a

miniature E.

histolytica

o No ingested

RBCs

Endolimax nana

• Cyst (left)

o No peripheral chromatin

o 4 nuclei with karyosomes

• Trophozoite (right)

o 6-10 microns

o Hard to distinguish from

Iodamoeba buetschlii

Iodamoeba buetschlii

• Cyst (left)

o No peripheral chromatin

o Prominent vacuole

• Trophozoite (right)

o 8-20 microns

o Vacuolated and granular

Giardia intestinalis (flagellate)

• Cyst (left)

o 4 nuclei

• Trophozoite (right)

o Pear shaped

o Central axoneme

o 2 nuclei

o 2 sucking disks

o 2 parabasa

Chilomastix mesnili (flagellate)

• Cyst (lower)

o "Shepherd's crook"

cytostome

• Trophozoite (upper

and right)

o Pear shaped

o Anterior end is

rounded, nucleus

o Posterior end is

tapered

o "Shepherd's crook"

cytostome

Dientamoeba fragilis

• No cyst

• Trophozoite

o Round

o Binucleate

o Internal flagellum

Balantidium coli (cilliate)

• Cyst

o Infrequently seen

• Trophozoite

o Large, up to 200 microns

o Cytostome and cilia

Kidney bean

Enterobius vermicularis

• Egg

o Thin walled oval with

flat side

o Found in scotch tape

prep rather than stool

Trichuris trichiura

• Egg

o Thick walls

o Bilateral polar plugs

Ascaris lumbricoides

• Egg

o Rough, bumpy surface

o Thick shell, stained with

bile

Hookworm

• Egg

o Necatur and Ancylostoma

eggs are indistinguishable

o "Steak on a plate"

Strongyloides stercoralis

• Worm (rhabditiform larva)

o Short buccal canal

o Bulbar portion of

esophagus

o Genital primordium

Taenia saginata

• Eggs are identical to T.

solium

o Around 30-40 microns

• Worm

o Smooth scolex with

four suckers

o Proglottids

Longer than they are

wide

>13 uterine branches

Taenia solium

• Eggs are identical to T. saginata

• Worm

o Scolex with four suckers with armed

rostellum

o Proglottids

Longer than they are wide

<13 uterine branches

Diphylobothrium latum

• Eggs smooth with

shoulderless

operculum and

small knob

o Around 60 microns

• Worm

o Scolex is almond-

shaped with 2

sucking grooves

o Proglottids wider

than long

Hymenolepis diminuta

• Eggs have thin inner and

outer shells

o About 80 microns

o Polar filaments between

shells

o Embryo with hooklets

inside inner shell

Hymenolepis nana

• Eggs

o About 40 microns

o Two shells with polar filaments between

o Oncosphere has six hooklets