MICRO Superficial Wounds/ Mycology

Question 1

Provide an example of how the skin inhibit pathogens

Answer 1

• acid pH produced by fatty acids of the sebaceous gland
• gram positive bacteria (skin flora) convert fatty acids/ lipids to unsaturated fatty acids = INHIBIT GRAM NEG BACTERIA and FUNGI

Question 2

List obligate skin pathogens

Answer 2

• S. aureus
• Candida sp.
• Enterobacteriaceae
• Beta hemolytic Streptococci
• Pseudomonas aeruginosa

Question 3

Which of the following microscopes is used for examination of calcofluor white stained slides?

a.
Bright field

b.
Fluorescent

c.
Polarizing

d.
Inverted

Answer 3

b.
Fluorescent

Question 4

The following results are recorded from a cat bite swab:
Direct Smear:

3+WBC
3+ RBC
1+EPI
4+GNB
1+GPCCL
Culture:
BAP: 4+ small grey non-hemolytic
1+ small white opaque
CAPCO2: 4+ small grey non-hemolytic
1+ small white opaque
MAC: no growth

Which of the following organisms is the most likely pathogen?

a.
Staphylococcus aureus

b.
Toxoplasma gondii

c.
Pseudomonas aeruginosa

d.
Pasteurella multocida

Answer 4

d.
Pasteurella multocida

Question 5

Which of the following organisms produces an oxidative reaction in the O-F test?

a.
Serratia marscesens

b.
Pseudomonas aeruginosa

c.
Staphylococcus epidermidis

d.
Morganella morganii

Answer 5

b.
Pseudomonas aeruginosa

Question 6

Which of the following organisms is / are fastidious gram negative bacilli? Select all that apply:

a.
Legionella sp

b.
Francisella sp

c.
Haemophilus sp

d.
Brucella sp

Answer 6

b.
Francisella sp

c.
Haemophilus sp

Question 7

Which of the following antimicrobials identifies MRSA?

a.
Cefoxitin

b.
Cefazolin

c.
Oxacillin

d.
Methicillin

Answer 7

a.
Cefoxitin

Question 8

Organism with “ASB” colonial morph

Answer 8

Bacillus sp.

Question 9

Organism with “pyo” colonial morph

Answer 9

Pseudomonas aeruginosa

Question 10

Francisella tularensis is a level __ organism.

Answer 10

Francisella tularensis is a level THREE organism.

Question 11

Typical results for Pseudomonas aeruginosa (TSI, motility, 42C growth, oxidase)

Answer 11

TSI: K/K
Motility: pos
Growth at 42C: pos
Oxidase: pos

Question 12

Which of the following results require immediate attention when working with Bacillus spp?

a.
Catalase positive

b.
Non-hemolytic

c.
Lecithinase positive

d.
Lipase negative

Answer 12

b.
Non-hemolytic

NOTE: Bacillus cereus

Question 13

Which of the following techniques is most useful for direct examination of skin, hair or nails for fungal infection?

a.
Gram stain

b.
Ziehl-Neelsen stain

c.
10% KOH

d.
India ink

Answer 13

c.
10% KOH

Question 14

Which of the following antimicrobials is the best option for an MRSA wound infection?

a.
Vancomycin

b.
Metronidazole

c.
Colistin

d.
Penicillin

Answer 14

a.
Vancomycin

Question 15

test results to ID S. pyogenes

Answer 15

cat -
PYR +
latex A
CAMP -
Taxos A Sensitive

Question 16

test results to ID P. aeruginosa

Answer 16

% = gnb
TSI = K/K
OF = oxidative
Wet mount motil = pos
Ox = pos
Nitrate = pos
TSB 42°C = pos
UV = pos

Question 17

What is the nitrate reduction test ?

Answer 17

add reagent A+B turns red = pos (nitrATES -> nitRITES)

if neg, add zinc:

red w zinc = neg (no nitrites)
white w zinc = pos (reduced further)

Question 18

tests to ID yeast

Answer 18

• direct smear
• CAC
• germ tube
• MALDI TOF

Question 19

Test results to ID Pasteurella multocida

Answer 19

%= gncb
Ox= pos
CAT= pos
TSI= A/A
Spot indole= pos

NOTE: animal bites

Question 20

What can happen if the germ tube test is incubated for >2.5 hrs ?

Answer 20

Candida sp. produces pseudohyphae= FALSE POS