Fungi

Question 1

What are Fungi?

Answer 1

unlike bacteria - they are eukaryotes and posses a nuclear membrane and membrane bound organelles, such as endoplasmic reticulum and mitochondria

Question 2

what do fungi look like?

Answer 2

• plant-like forms but lack defined root or leaf structures and are non-photosyntheitic

Question 3

what is their kingdom?

Answer 3

they are assigned their own - Mycota

Question 4

what are Yeast forms?

Answer 4

single, unconnected vegetative cells which grow in a manner similar to bacteria (but they grow ten times faster)

Question 5

How do Yeast reproduce?

Answer 5

by budding

Question 6

What don’t Yeast do?

Answer 6

they do not sporulate and are not much of a hazard to lab workers

Question 7

What are filamentous fungi (/molds)?

Answer 7

consist of a complex mass (mycelium) composed of tubes called hyphae

Question 8

How do hyphae reproduce?

Answer 8

by the formation of spores which are released in enormous numbers from the mycelium

Question 9

What happens to these spores?

Answer 9

can become airborne and present a contamination hazard in labs working on pathogenic molds

Question 10

How can spores be formed?

Answer 10

asexually or sexually
asexually - most common way and are called Conidia
Sexual = ascospores

Question 11

What happens when the hyphal filaments are packed densely?

Answer 11

the mycelium can appear to be cohesive tissue, as in the case of mushrooms

Question 12

what do Fungi produce?

Answer 12

Fungi are saprophytic or parasitic and procude a variety of unusual metabolic products, some of which are highly toxic to higher animals

Question 13

How do you identify fungi?

Answer 13

Medically important fungi = ID depends upon microscopic examination of the morphology, particularly of sporulating forms “by their fruits ye shall know them”
- biochemical tests / sophisticated technologies can also be used

Question 14

What are dimorphic fungi?

Answer 14

fungi which have both yeast and filamentous phases, usually dependent on temperature or other growth conditions

Question 15

Taxonomy: why is the classification of fungi difficult?

Answer 15

complicated because many fungi can reproduce both sexually and asexually
= the morphological charactristics are different for each stage, and since speciation was established on the microscopic morphology, the sexual and asexual stages of teh same ogranism may actually have different species names

Question 16

Taxonomy: Asexual stage name?

Answer 16

anamorphic

• asexual = budding
• a group of fungi which only an anamorphic (asexual) form is known and these are termed the Fungi Imperfecti

Question 17

Taxonomy: why called fungi imperfecti?

Answer 17

because they reproduce in a non-sexual manner and God declares sexual is the perfect / correct way of producing

Question 18

Taxonomy: Sexual stage name?

Answer 18

telomorphic

Question 19

For clinical purposes how can fungi be classified?

Answer 19

into: yeasts, molds, dimorphic fungi and poisonous mushrooms

Question 20

What is a kerion?

Answer 20

a large mat of fungal infection

Question 21

what is jock itch caused by?

Answer 21

Trichophyton mentagrophytes

Question 22

Athletes foot is caused by what?

Answer 22

dermatophytes - and the resulting skin fissuring may predispose infected patients to bacterial cellulitis

Question 23

most yeast infections are what?

Answer 23

endogenous - except for Cryptococcus neoformans - which is associated wiht teh excreta of gregarious birds - primarily pigeons

Question 24

What are the Predisposing Factors to Yeast infection? (Superficial)

Answer 24

1) wet work (dishwashers)
2) pregnancy, oral contraceptives (tight clothing)
3) diabetes mellitus
4) use of broad spectrum antibiotics
5) HIV infection, CD4 < 500
6) Dectin-1 (beta glucan receptor deficiency)

Question 25

What are the Predisposing Factors to Yeast infection? (Deep)

Answer 25

1) immunosuppression, especially corticosteroids
2) indwelling venous catheters
3) use of broad spectrum antibiotics
4) IV drug abuse
5) HIV infection, with CD4 < 200 ** (big point to remember)

Question 26

Diagnosis of Yeast

Answer 26

• microscopic examination with quick wetmount establishes the presence of yeast since they are much larger than bacteria
  next step: germ tube test which is speciifc for Candida albicans
• yeast is incubated for three hours at 37 degrees in a biological fluid

Question 27

Formation of germ tubes provides what?

Answer 27

definitive identification - if psoitive - no further tests are necessary
negative - yeast is planted on corn meal agar and examined after incubation

Question 28

What other tests may be necessary for yeast?

Answer 28

biochemical and carbohydrate assimilation tests may also be necessary

Question 29

Whats good about the germ tube test?

Answer 29

• any lab anywhere can do this - very simple

Positive = candida albicans

Question 30

Candida Albicans

Answer 30

extremely common - part of the normal flora of the oropharynx, vagina, bowel, and skin
- most common species causing infection

Question 31

in normal individuals - what does CA cause?

Answer 31

mild to severe or even chronic superficial infections of the skin - due to wet skin on skin (sweaty) = red patch, bit of a silvery shine under some light
KEY FEATURE = satellte lesion = little ones outside the main patch

Question 32

What are some examples of the superficial infections CA can cause?

Answer 32

(diaper rash, balanitis, infections of intertriginous areas), nails (onchomycosis) and mucous membranes (thrush - white patches in back of mouth, and vaginitis - cottage cheese-like discharge)

Question 33

in immunocompromised patients, what happens?

Answer 33

deep tissues can be infected to produce severe systemic disease (esophagitis, pyelonephritis, sepsis)
t

Question 34

Therapy ?

Answer 34

topical

vaginal = swallow fluconazole once and its done

Question 35

Cryptococcus neoformans var neoformans

Answer 35

get from being around birds

Question 36

what does neoformans cause?

Answer 36

• diffuse pulmonary infection - usually asymptomatic - but can also cause localized abseccess and granuloma formation in lung, brain, lymph nodes, skin and bone
• mainly associated with chronic meningitis in AIDS patients

Question 37

Cryptococcus Gattii

Answer 37

• causes localized abscesses (cryptococcomata) in the tropics
• associated with eucalyptus plants
• emerging problem in Pacific NW where it colonized in trees and soil
• 20% mortality, most commonly pneumonia, and most patients not immunocompromised