Quiz 5

Question 1

What is the shape of staph and strep?

Answer 1

Cocci for both

Question 2

What is the gram reaction of staph and strep?

Answer 2

gram + for both

Question 3

What is the arrangement of staph and strep?

Answer 3

strap: clusters
strep: chains

Question 4

Where is staph and strep found in the body?

Answer 4

staph: skin, nasal passage
strep: mouth, throat, vaginal area, GI tract

Question 5

Is staph and strep catalase positive or negative?

Answer 5

staph: catalase positive (facultative anaerobe)
strep: catalase negative (aerotolerant anaerobe)

Question 6

Reaction to cold or dryness for staph and strep?

Answer 6

staph: resistant
strep: sensitive

Question 7

What is the salt tolerance for staph and strep?

Answer 7

staph: osmotolerant
strep: not osmotolerant

Question 8

What is the percent of humans that carry S. epidermidis and S. aureus?

Answer 8

S. epidermidis: 100 percent
S. aureus: 25-30 percent of people (50 percent of healthcare workers)

Question 9

What is the pathogenicity of S. epidermis and S. aureus?

Answer 9

S. epidermidis: not pathogenic
S. aureus: pathogenic

Question 10

Is S. epidermidis and S. aureus normal flora?

Answer 10

S. epidermidis: normal flora
S. aureus: 2/3 of people carry it sometimes

Question 11

Is S. epidermidis and S. aureus a fermenter of mannitol (sugar)?

Answer 11

S. epidermidis: no
S. aureus: yes

Question 12

Is there a coagulase reaction with S. epidermidis or S. aureus?

Answer 12

S. epidermidis: negative
S. aureus: positive

Question 13

What are the three main virulence factors of staph?

Answer 13

coagulase
b-hemolysin
staphylokinase

Question 14

What is coagulase?

Answer 14

forms clots (97% of staph)
- forms a clot and helps to protect bacteria from immune system

Question 15

What is B-hemolysin?

Answer 15

digests red blood cells and uses the contents for food and multiplies
- digests RBCs for food

Question 16

What is staphylokinase?

Answer 16

dissolves clot
- allows for spread to neighboring tissues

Question 17

What levels of staph infection are there?

Answer 17

-skin diseases
- sepsis
- pneumonia
- necrotizing fasciitis
- food poisoning

Question 18

What is the purpose of the mannitol salt agar?

Answer 18

to presumptively identify staphylococcus aureus and select for the growth of salt tolerant bacteria

Question 19

Why is beef extract included in the MSA recipe?

Answer 19

peptones, general growth

Question 20

Why is sodium chloride included in the MSA recipe?

Answer 20

selective for osmotolerant organisms

Question 21

Why is D-mannitol included in the MSA recipe?

Answer 21

fermentation to produce acids, differential

Question 22

Why is phenol red included in the MSA recipe?

Answer 22

pH indicator; pink = alkaline, yellow is acidic

Question 23

What does a yellow agar on the MSA mean?

Answer 23

acidic pH -> bacteria metabolized the mannitol and produced acidic products
- presumptive S. aureus
- could be micrococcus (non-pathogenic)
- can determine S. aureus by coagulase

Question 24

What does a red or pink agar on the MSA mean?

Answer 24

alkaline pH -> bacteria did NOT metabolize mannitol, but instead used peptones as a food source (osmotolerant)
- could be S. epidermis (-)

Question 25

What does no growth mean on the MSA?

Answer 25

no osmotolerant bacteria (-)

Question 26

What is the purpose of the coagulase test?

Answer 26

to test whether bacteria produce coagulase (like S. aureus) - confirmatory test after MSA agar

Question 27

What is the substrate for the coagulase test?

Answer 27

Fibrinogen - clotting factor that is liquid and the source is rabbit plasma

Question 28

What is the exoenzyme in the coagulase test?

Answer 28

coagulase

Question 29

What is the products for the coagulase test?

Answer 29

Fibrin clot (solid)

Question 30

What is a positive and negative of the coagulase test?

Answer 30

positive: solid product negative: liquid product

Question 31

What is the purpose of the CAMP test?

Answer 31

to identify and confirm the presence of group B strep - streptococcus agalactiae

Question 32

What were the 5 organisms tested in the CAMP test?

Answer 32

- Streptococcus agalactiae: causes serious infection in newborns - Streptococcus pyogenes: causes strep throat - Streptococcus mutans: causes cavities - Enterococcus faecalis: in GI tract - Streptococcus pneumoniae: causes pneumonia

Question 33

What is the purpose of the bile esculin agar?

Answer 33

to select for the growth of enterococcus for presumptive identification

Question 34

What are the ingredients used in the recipe for the bile esculin agar and what is each used for?

Answer 34

- peptones; general growth - oxgall (bile salts); inhibit gram +, except enterococcus (selective) - sodium azide; inhibits gram - (selective) - esculin: has glucose and is a special food source; differential for E. faecalis - ferric citrate: turns brown with esculetin (product of esculin digestion)

Question 35

What does growth, but not brown on the bile esculin agar mean?

Answer 35

growth, but not brown = enterococcus but not E. faecalis

Question 36

What does growth and brown on the bile esculin agar mean?

Answer 36

presumptive E. faecalis

Question 37

What is the M protein?

Answer 37

It was classified by rebecca lancefield and it has antiphagocytic properties that allow bacteria to stick to surfaces

Question 38

What is beta hemolysis?

Answer 38

complete destruction of RBCs (get clear zones around colonies) - group A and B strep

Question 39

What is alpha hemolysis?

Answer 39

partial destruction of RBCs (get green zones around colonies) - streptococcus pneumoniae

Question 40

What is gamma hemolysis?

Answer 40

no damage to RBCs (no change to agar) - S. mutans and Group D strep

Question 41

What diseases are associated with streptococcus pyogenes and what classification of strep is it?

Answer 41

strep throat, scarlet fever, necrotizing faciitis group A: beta hemolytic

Question 42

What diseases are associated with streptococcus agalactiae and what classification of strep is it?

Answer 42

major neonatal pathogen, leading to pneumonia, sepsis, meningitis group B: beta hemolytic

Question 43

What diseases are associated with enterococcus faecalis and what classification of strep is it?

Answer 43

found normally in gut and infections may result in areas of the body outside of the GI tract group D: gamma hemolytic

Question 44

What disease are associated with streptococcus mutans and what classification of strep is it?

Answer 44

cavities non-lancefield: gamma hemolytic

Question 45

What diseases are associated with streptococcus pneumoniae and what classification of strep is it?

Answer 45

causes pneumonia non-lancefield: alpha hemolytic

Question 46

What is a positive test for the CAMP test?

Answer 46

look for triangular zone of enhanced beta hemolysis (synergistic)

Question 47

What is a positive for antibiotic sensitivity in the CAMP test?

Answer 47

clearing around the disk

Question 48

What is used to identify strep pneumoniae?

Answer 48

optochin sensitivity

Question 49

What is used to identify strep pyogenes?

Answer 49

bacitracin sensitivity

Question 50

What is used to identify strep agalactiae?

Answer 50

CAMP positive

Question 51

What is used to identify enterococcus faecalis?

Answer 51

bile esculin positive

Question 52

What is used to identify strep mutans?

Answer 52

negative to all tests

Question 53

What is mycology?

Answer 53

study of fungi

Question 54

What are the differences between yeast and mold?

Answer 54

yeast: - unicellular -colonies resemble bacteria - reproduce by budding (asymmetrical division) molds: - multicellular - colonies have velvety or fuzzy appearance - hyphae: filaments for nutrient absorption - filamentous - thread like - reproduce using spores either asexually or sexually

Question 55

What is a medically important yeast?

Answer 55

Candida albicans - causes yeast infection = candidiasis

Question 55

Who is most susceptible to candida infections?

Answer 55

- diabetics - those with immunodeficiency - catheterized patients - infants - individuals taking antimicrobial medications

Question 56

What is a nonpathogenic yeast?

Answer 56

Saccharomyces cerevisiae - brewers yeast - used to produce beer, wine, and bread - fermentation produces CO2 gas and ethanol

Question 57

What are the three types of molds?

Answer 57

rhizopus stolonifer - black bread mold - hyphae are coenocytic (multinucleated cells) - reproduce asexually (sporangiospore) or sexually (zygospore) penicillium notatum - medically important mold - spores are green and hyphae are white

Question 58

Why is fungi grown on saburaud's dextrose agar (SAB)?

Answer 58

low pH of 5 or 6 encourages fungi to grow and not bacteria