pt 3 (testing for dermatophytes)

Question 1

what are the functions of each of the 2 chemicals in the Fungassay media?

Answer 1

change the pH (changes agar color)
inhibit bacteria

Question 2

describe the correct procedure for collecting a sample from an animal that will be tested for the presence of dermatophytes (5-8 steps)

Answer 2

1. clean site (lay alcohol soaked gauze over site, remove and let air dry)
2. use hemostat to remove larger debris from edge of lesion
3. trim off piece and make fine shavings with a scalpel

Question 3

explain how to do the Fungassay test after a sample is obtained (inoculation, incubation, when to read results, how to identify any organisms that grow)

Answer 3

inoculation: flame loop, collect sample, transfer to agar (do not bury or close lid completely to allow airflow)

incubation: room temp, monitor everyday for growth

interpretation: 2-3 days agar color change is complete; dermatophytes induce fast color changing and colonies will be small

Question 4

how does the fungassay medium change when the dermatophytes are growing vs when contaminants are growing?

Answer 4

contaminants cause slow color changing - amber to red color because of alkaline wastes

Question 5

how does the colony color and texture of dermatophytes differ from that of contaminants?

Answer 5

dermatophytes (white or cream or tan, flat); contaminants (fluffy, tall, white - can change color)

Question 6

explain the procedure for identifying fungi from a sample taken from an animal without culturing it first; what is the chemical you need to mix the sample with?

Answer 6

mixed with 10 % NaOH solution gently warmed with a flame for 10 seconds on a slide to clear debris

Question 7

microsporum canis

Answer 7

rough edges, 6-13 septa

Question 8

microsporum gypseum

Answer 8

thin walled, 2-6 septa, more uniform and neat

Question 9

trichophyton

Answer 9

zoonotic; clusters, corkscrew appearance, cigar shaped with 5-6 septa

Question 10

aspergillus

Answer 10

dandelion, thicker than penicillium

Question 11

penicillium

Answer 11

broom or long hand similar to aspergillus

Question 12

rhizopus

Answer 12

large, round head on stalk, arise from single point

Question 13

alternaria

Answer 13

hand grenade or tennis racket on stalk

Question 14

fusarium

Answer 14

canoes smaller than microsporum

Question 15

yeast

Answer 15

footprint

Question 16

hyphae

Answer 16

filaments that compose the body of a fungus

Question 17

conidia

Answer 17

an asexual spore

Question 18

mycelium

Answer 18

a mat made up of intertwining thread-like hyphae

Question 19

describe how to prepare a slide from a fungal or contaminant colony and identify the organism

Answer 19

1. 1-2 drops pf stain on slide
2. flame wire loop
3. use loop to remove growth from culture
4. mix with stain
5. place cover slip
6. 10X or 40X to look on edges of clumps

Question 20

what is the name of the stain used when looking at fungi microscopically?

Answer 20

lactophenol cotton blue stain