Bacteriology: Mycology

Question 1

What is the cell membrane and cell wall of fungus made of?

Answer 1

Cell membrane has ergosterol rather than cholesterol
Cell wall made of chitin

Question 2

What characteristic of chitin makes it easy to infect animals?

Answer 2

It is difficult to digest but it cannot make their own energy

Question 3

What is yeast?

Answer 3

unicellular form of a fungus

Question 4

What is hyphae?

Answer 4

filamentous form of fungus

Question 5

What are pseudohyphae?

Answer 5

chains of yeast that look like hyphae

Question 6

What is mold?

Answer 6

a fungus that grows as a mass of hyphae (mycelium)

Question 7

What are dermatophyte?

Answer 7

fungal organism that causes ringworm

Question 8

What are endospores?

Answer 8

spore contained within a sac

Question 9

What are dimorphic fungus?

Answer 9

fungi that exist as yeast forms in animal tissues & as hyphae in environment due to temperature differences.

Question 10

What are the 3 main ways that fungi grow?

Answer 10

1) budding yeast
2) germinating spore/conidia
3) fruiting body

Question 11

What are the characteristics of budding yeast?

Answer 11

broad-based
narrow-based
asexual reproduction by budding
the type of budding allows us to differentiate between different oranisms

Question 12

What are the characteristics of germinating spore/conidia?

Answer 12

forms germ tube that can grow into a new organism

Question 13

What are the characteristics of fruiting body?

Answer 13

produce many conidia that are each very tiny & light & can be dispersed through the environment

Question 14

How can fungi spread?

Answer 14

locally by the release of conidia
aerosolized by the release of conidia into the air

Question 15

What gives rise to the patchy appearance of mold?

Answer 15

The local and aerosolized spread of conidia

Question 16

What are the 2 types of hyphae?

Answer 16

Septate & nonseptate

Question 17

What are the characteristics of septate hyphae?

Answer 17

They have lines (septum) that divide the hyphae into “sections”

Question 18

What are the characteristics of nonseptate hyphae?

Answer 18

There are no lines that divide the hyphae into section

Question 19

What types of conidia do Dermatophytes have

Answer 19

Arthroconidia and macroconidia and microconidia

Question 20

What are arthroconidia?

Answer 20

observation in patients
spores release during hyphal fragmentation

Question 21

What are macroconidia?

Answer 21

observed in lab
big
allows for differentiation between dermatophyte species

Question 22

What types of growth and reproduction do other fungi species have?

Answer 22

Fruiting bodies, clusters, small little buds

Question 23

What are the factors that affect the development of fungal disease?

Answer 23

Virulence factors
Tissue affected
Host immunity
Geographic location
Environment

Question 24

How do we diagnose fungal infections?

Answer 24

Presumptive
Direct swab/observation
Culture
Antibody detection
Antigen detection

Question 25

What is the best diagnostic technique for superficial skin samples?

Answer 25

wet mount cytology

Question 26

What is the mounting fluid solution used for wet mount cytologies?

Answer 26

10% potassium hydroxide which clears cellular debris New methylene blue lactophenol cotton blue

Question 27

What types of stain do we use for routine fungal samples?

Answer 27

Diff-quick Wright-Giemsa H&E

Question 28

What types of stain do we use for special fungal samples?

Answer 28

Gamori's methenamine silver: fungal wall takes up silver in the stain and appear black Periodic acid-schiff (PAS)

Question 29

What techniques can we use in direct exam/observation?

Answer 29

Wet mount cytology Stain/Reaction Cytology Impression smear Histopathology

Question 30

What is the biggest draw back with fungal cultures?

Answer 30

They can take way to long and this can be dangerous with sever infections. Normal fungal culture can take 4 weeks or more

Question 31

What samples can we collect to send OUT and which is the best?

Answer 31

Fresh tissue/ fluid--BEST Swabs-- only when you cannot get a better sample

Question 32

What sort of transport conditions are necessary for samples to be sent OUT?

Answer 32

Overnight shipping to lab dermatophytes: hair/nails/scales/ skin in a sterile container @ room temp Room temperature samples if fungal disease is primary differential send chilled on ice if bacterial contamination or differential

Question 33

What are the test that can be done IN-HOUSE?

Answer 33

DTM: dermatophyte test media RSM: rapid sporulation media

Question 34

What are the characteristics/ draw backs of DTM?

Answer 34

has a pH indicator in media starts yellow but changes to red/pink with growth of dermatophytes false positives can occur if you wait to long to read results

Question 35

Why does the DTM media change color?

Answer 35

pH change occurs when organism eats protein in agar resulting in an ammonia by product, increasing the pH, allowing the agar to change color

Question 36

What are the infectious species of dermatophytes?

Answer 36

Mycosporum spp Trichophyton spp.

Question 37

What disease does dermatophytes cause?

Answer 37

Ringworm

Question 38

What are the clinical signs of dermatophtophytosis?

Answer 38

Hair loss Scales Crusts Red skin Pruritis Papules/pupstules

Question 39

How can you diagnose Dermatophytosis?

Answer 39

Woods lamp Cytology (wet or dry))

Question 40

What liquid is used typically used for a wet mount dermatophyte cytology?

Answer 40

Potassium hydroxide

Question 41

What makes DTM turn red?

Answer 41

It has phenol red indicator in it

Question 42

How long does it take for a DTM to become positive?

Answer 42

3-7 days

Question 43

What causes false positive readings with DTMs?

Answer 43

age-- not reading it in the correct time frame

Question 44

What type of mycoses does dermatophytes cause?

Answer 44

cutaneous mycoses

Question 45

What type of mycoses does sporotrichosis cause

Answer 45

cutaneous mycoses that can become systemic

Question 46

What is the dimorphic fungus that is a sporotrichosis?

Answer 46

Sporothrix schenckii

Question 47

What type of fungus is Sporothrix schenckii

Answer 47

dimorphic fungus

Question 48

Where does Sporothrix schenckii like to live?

Answer 48

soil, dead vegetation, and roses

Question 49

What is the typical host of Sporothrix schenckii?

Answer 49

Cats

Question 50

What must a patient have in order to become infected with sporotrichosis?

Answer 50

and abrasion or puncture/wound

Question 51

How are sporotrichosis diagnosed and what does it look like?

Answer 51

Usually diagnosed through histopathology and there will be macrophages with ovid yeast in them

Question 52

What type of mycoses does blastomyces dermatitidis, histoplasma, cryptococcus, and coccidiodes cause?

Answer 52

respiratory mycoses that becomes systemic

Question 53

What are the characteristics of Blastomyces dermatitidis?

Answer 53

Yeast stain big and blue with broad based budding and are found in wet environments like river valleys

Question 54

What are the characteristics of Histoplasma?

Answer 54

Many yeast inside of macrophages and are a associated with bat dropping and can be found in the midwest

Question 55

What are the characteristics of cryptococcus?

Answer 55

Yeast have a big thick capsule and are found all throughout the U.S

Question 56

What are the characteristics of coccidioides?

Answer 56

Endospores and are found in the southwestern U.S.

Question 57

What is the pathogenesis of dermatitidis, histoplasma, cryptococcus, and coccidiodes?

Answer 57

Starts with inhalation of the spore & goes to the lungs then from the lung it is picked up and taken to the lymph system from there the spore can then invade the host cells if they normally do that then the phagocytic cells then carry it around through the lymph & blood to other sites

Question 58

What are the common sites of systemic infection?

Answer 58

Bone & Brain Eyes Lymphnodes & lungs Skin