MICRO EXAM 2 CH14

Question 1

When do you see arrangement morphology on media?

Answer 1

Direct smear

Question 2

When do you not see arrangement morphology on media?

Answer 2

Indirect smear

Question 3

Which Staphylococcus spp. is coagulase pos?

Answer 3

S. aureus

Question 4

Which Staphylococcus spp. is coagulase neg?

Answer 4

S. epidermidis
S. saprophyticus
S. haemolyticus
S. legdunesis

Question 5

Characteristics of Staphylococcus spp.?

Answer 5

Non-motile
Non-spore forming
Non-encapsulated
Aerobic
Oxidase Neg
Bacitracin R (Taxo A)

Question 6

Primary reservoir of S. aureus?

Answer 6

Nares; also vagina, pharynx and skin surfaces

Question 7

Mode of transmission of S. aureus?

Answer 7

Traumatic introduction
Direct Contact
Inanimate objects
Indueling devices
Immune response defects

Question 8

What are the 6 virulence factors of S. aureus?

Answer 8

Enterotoxins
Toxic Shock Syndrome
Toxin 1 (TSST)
Exfoliatin toxin
Cytolytic toxins
Extracellular enzymes
Protein A

Question 8

Enterotoxins

Answer 8

Vomiting and diarrhea/food poisoning

Question 9

TSST

Answer 9

Superantigen stimulating T-cell proliferation and cytokines.
Seen in nearly all menstruation associated TSS.

Question 10

Exfoliatin toxin

Answer 10

Epidermolytic toxin
Scalded skin syndrome

Question 11

Cytolytic toxins

Answer 11

4 hemolysis (alpha beta, gamma, delta)
1 Leukocidin

Question 12

What is the toxin for leukocidin called?

Answer 12

Panton-Valentine Leukocidin (PVL)
Causes cutaneous infections, necrotizing pneumonia.

Question 13

Extracellular eznymes

Answer 13

Hyaluronidase
Lipase
Staphylocoagulase

Question 14

Protein A

Answer 14

Cell wall component
Binds to Fc on IgG
Inhibits phagocytosis

Question 15

How is S. epidermidis predominantly aquired?

Answer 15

HAI via catheters, shunts, and heart valves.

Question 16

Types of skin/wound infections caused by S. aureus?

Answer 16

Folliculitis
Furuncles (boils)
Carbuncles
Impetigo
Scalded skin
syndrome/Ritter disease
Abscess

Question 17

What does S. epidermidis need to become pathogenic?

Answer 17

Biofilm

Question 18

What source does S. saprophyticus come from?

Answer 18

Urine

Question 19

Significance of S. lugdunensis?

Answer 19

Contains mecA gene that makes it resistant to methicillin.
Mocks S. aureus

Question 20

What media does Staphylococci grow easily on?

Answer 20

BAP or thioglycollate

Question 21

What other medias can you grow Staphylococci on?

Answer 21

MSA, CNA, PEA and chromagar

Question 22

Pos thioglycollate in broth result?

Answer 22

Cloudy with streamers

Question 23

Direct gram stain results?

Answer 23

GPC in clusters and WBC

Question 24

Colony morphology of S. aureus?

Answer 24

Round White to golden creamy Beta-hemolysis

Question 25

Colony morphology of S. epidermidis?

Answer 25

Small-medium sized Gray to white Non-hemolytic

Question 26

Colony morphology of S. saprophyticus?

Answer 26

Medium sized White to slight yellow

Question 27

What biochemical test is used to differentiate Staph from Strep?

Answer 27

Catalase

Question 27

How many seconds after beginning catalase test do you read results?

Answer 27

20 sec

Question 28

What would give you a false pos catalase test?

Answer 28

Gouging the BAP media onto slide when performing catalase test. RBC react with H2O2.

Question 29

What are the 3 types of coagulase tests?

Answer 29

Slide Coagulase Tube Coagulase Rapid Coagulase

Question 30

What does slide coagulase test detect?

Answer 30

Cell-bound clumping

Question 31

What does tube coagulase test detect?

Answer 31

Free coagulase/staphylocoagulase

Question 32

What does rapid coagulase test detect?

Answer 32

Clumping factor and protein A

Question 33

What Staph sp. is coagulase pos?

Answer 33

S. aureus

Question 34

What test can differentiate S. saprophyticus from other Staph spp.?

Answer 34

Novobiocin susceptibility test

Question 34

What is the result on novobiocin test for S. saprophyticus?

Answer 34

If zone of inhibition is less than 16mm (resistant)

Question 35

Related genus to Staphylococcus?

Answer 35

Micrococcus

Question 35

Biochemical test results for micrococcus?

Answer 35

Catalase Pos Coagulase Neg

Question 35

What biochemical test is used to detect Micrococcus?

Answer 35

Microdase disc

Question 36

What antibiotic is resistant to S. aureus?

Answer 36

Penicillin (MRSA)

Question 37

Why is S. aureus resistant to penicillin (methicillin)?

Answer 37

Beta lactamase enzyme

Question 38

What virulence factor causes oxacillin resistance?

Answer 38

MecA gene

Question 39

*Review* If erythro R and clinda S, what do you do?

Answer 39

Perform D-test

Question 40

*Review* Pos D-test results for erythro and clinda?

Answer 40

No ZOI for erythro, D shape ZOI for clinda

Question 41

*Review* Neg D-test results for erythro and clinda?

Answer 41

No ZOI for erythro, circular ZOI for clinda

Question 42

Rapid methods for detecting MRSA and MSSA?

Answer 42

RT-PCR and/or MALDI-TOF