Mycology Introduction

Fungi exist as …

Molds, Yeasts, or Dimorphic fungi

Mold vs Yeast

Mold =

• Multicellular

• Sexual or Asexual reproduction (spores / conidia)

• Hyphae → Fuzzy / Wooly colonies

• Various colors

Yeast =

• Single-celled

• Asexual reproduction = Budding (blastoconidia)

• Pseudohyphae (formed by continous budding) or No hyphae

• White, smooth, “bacteria-like” colonies

Dimorphic fungi =

Fungi that has a yeast + mold phase

Grows as Yeast at Body temp. (37°C in vitro + in vivo)

Grows as Mold at Room temp. (22-30°C in vitro)

most common yeast isolated from blood cultures =

Candida spp.

if testing is delayed, how do you store CSF?

keep at Room Temp.

how to process nail vs skin specimen

Nails : dissolve w/ 20% KOH + may need to use heat

Skin : break down w/ 10% KOH

Why is it important to know how a urine specimen was collected for culture?

Clean Catch : some normal flora contamination is normal ; >100,000 CFU/mL is considered a UTI

Catheter : NO normal flora contamination should occur ; any growth is a concern

purpose of using KOH

KOH dissolves human cells lacking keratin cell walls (hair, nails, skin)

leaves any fungus to be viewed

Calcofluor White stain

Fluorescent blue stain → binds to Fungi cell walls

causes fungal elements to fluoresce under fluorescent scope

(used w/ KOH)

India ink is used on what specimen to identify what fungus ?

India ink stains Cryptococcus neoformans in CSF

• C. neoformans has visible “Halo” = thick capsule lacks india ink surrounding fungi

what stain is used for Fungal tease or cellophane mounts?

Lactophenol aniline blue

Most common media used to culutre fungi =

Sabouraud dextrose agar (SDA)

Sabouraud Dextrose Agar (SDA / SAB) media

Non-selective media for Fungi cultures

• acidic pH inhibits bacteria growth

incubation temperature for Fungal cultures

30°C

Rugose vs Verrucose colonies

Rugose = wrinkles, corrugated

Verrucose = rough elevations

Umbonate colony appearance =

“Round knob” above media

Mycelium =

network of hyphae (fungal threads)

Aerial vs Vegetative Hyphae

Aerial Hyphae =

• Reproductive (produce conidia)

• Above media surface

Vegetative Hyphae =

• Inside media → Absorbs nutrients inside agar

  

What is the name for this hyphae structure?

Racquet hyphae = enlarged, club-shaped

What is the name for this hyphae structure at the bottom?

Rhizoid hyphae = “Root-like” hyphae that grow on stolons

Hyaline vs Dematiaceous hyphae

Hyaline = BLUE stained (Nonpigmented hyphae)

Dematiaceous = BROWN stained (dark pigmented due to melanin in cell wall)

Conidiogenous cells =

Conidiogenous cells are attached to Conidiophore (extension of hyphae)

Conidiogenous cells produce Conidia (spores)

Phialides =

“Vase-like” structures → attached to conidiophores ; produce phialoconidia

Uniseriate vs Biseriate phialides

Uniseriate = One row of phialides

Biseriate = Two rows of phialides

• bottom row = Metulae

Annellides =

similar to phialides, but have rings around tip (where annelloconidia forms) 

annelloconidium can become spiny (echinulate) w/ age

Sporangium

Sac-like cell containing spores 

• form on Sporangiophores + produce Sporagniospores

Columella

Structure that spores attach to inside sporangium 

Micro- vs Macroconidia

Microconidia = small, unicellular spores

Macroconidia = larger, multi-septate spores

Arthroconidia

spores formed by fertile Hyphae Fragmentation

Blastoconidia vs Chlamydoconidia

both = asexual reproduction of YEAST

Blastoconidia =

• spores produced by budding

• develop in clusters along hyphae

Chlamydoconidia =

• thick-walled survival spores forming under certain growth conditions

• Terminal, Sessile, Intercalary chlamydospores form at tips, side, or inside hyphae

Differentiate the types of Chlamydocondia → Terminal, Sessile, Intercalary

based on location in relation to Hyphae

Terminal = tip

Intercalary = inside

Sessile = on the side

Pseuodhyphae =

structure of YEAST

• yeast budding continues w/out conidia separation → forms long filament of attached blastoconidia

• shows constrictions between cells (TRUE hyphae = NO constrictions w/ parallel sides)