Laboratory Diagnostic in Medical Laboratory Diagnostic in Medical MycologyMycology

INTRODUCTION Daily responsibilities of the clinical microbiology

laboratory Opportunistic fungi is increasing at an impressive

rate Laboratory technologists must recognize large

group of potential fungal pathogen

Detection and recovery of fungi from clinical specimens

Dermatophytosis and Agents of Superficial Mycosis Specimen and direct microscopic examination Skin, nail scraping and hair shaft Placed in one or two drops of 10-20% KOH A cover slip is placed on top and the preparation is heated gently Nails may require a strong alkali solution (25%KOH)

and long clearing time N. B. combination of KOH plus Dimethyl sulfaoxide

(DMSO) may be used for nail specimens

OBSERVATIONS

Hair

Endothrix hair invasion Ectothrix hair invasion

KOH microscopic examination of skin or nail

Skin or nail

Isolation media

1. SDA plus antibiotics and cycloheximide (SDACGC)2. SDACG) SDA Plus Antibiotics Identification of etiologic agents Colony characteristics Color of the surface and reverse of colony texture of the surface (powdery, granules,

woolly, cottony) rate of growth

Observation

Trichophyton violaceum• Color Pink• Texture Waxy Microscopic canis• Color White with yellow

reverse color• Texture Woolly

Observation

Trichophyton rubrum• Color White with brown to red

reverse color• Texture downy to

fluffy

Microscopic morphology

Arrangement and type of the conidia macroconidia or macroconidia other structure determine by teased mounts or slide

culture preparations mounted in lactophenol cotton blue special media used such as Corn Meal Agar or Potato Dextrose Agar to stimulate sporluation.

Microscopic morphology

Macroconidia of microsporum canischlamydospore of T. violaceum

Microconidia of T. rubrum

Pityriasis versicolor (Tinea versicolor)

A. Direct microscopic examination Skin scrapings are mounted in

10% KOH plus India ink or in lactophenol Cotton blue.

Observation Short hyphae spaghetti like

appearance Curved hyphae and yeast cells

A. Isolation media SDACG plus 2% Olive oil or

Tween 80

Identification of yeast of medical importance with reference to

Candida spp using the following schemeGerm tube test

Negative positive

Corn meal agar mostly C. albicans

+ChlamydosporesHyphae absent hyphae present

Unease test arthroconidia (+) blastoconidia (-)

Trichosporon species or geotrichum spp Candida spp

Biochemical tests

(+) (-)Small cells or large cell

C. glabrate S. cervisiae

Mucoid with Capsule or red with capsule

Cryptococcus spp Rhodoturula spps

Identification of C. albicans and other Candida species

a. Gram stain Gram positive oval or round shapeb. Germ tube test A small portion of an isolate colony suspended in a test tube containing 0.5

ml of rabbit or human serum or plasma The test tube is inoculated at 30C for 2-

3hr examined microscopically for the

presence of germ tubesN.B: Other Candida species produce

pseudohyphae and true hyphaeC. glabrate produces yeast form only

Observations: C. albicans produce germ tube

Identification of C. albicans and other Candida species

c. Chlamydospore production For the differentiation of C. albicans

from other Candida species using Corn Meal Agar plus 0.02 %

Tween 80 Observation C. albicans produce chlamydospore

after 24hr incubation at room temperature, while other Candida species produce only pseudohyphae and true hyphae.

N. B. C. glabrate produces yeast form only

Aspergillus

Colony appearanceMicroscopic appearance

Structure of Aspergillus

Microscopic appearance

Zygomycosis

Colony appearance

Microscopic appearance

structures