AST (TABLE)

Question 2

Standard inoculum density for bacterial AST? a. 1.0 x 10^6 CFU/mL b. 1.5 x 10^8 CFU/mL c. 5.0 x 10^5 CFU/mL d. 3.0 x 10^8 CFU/mL

Answer 2

b

Question 3

Turbidity standard used for disk diffusion inoculum? a. 1.0 McFarland b. 2.0 McFarland c. 0.5 McFarland Standard d. Saline blank

Answer 3

c

Question 4

Standard medium used for Kirby Bauer method? a. Blood agar b. Chocolate agar c. Mueller-Hinton Agar d. TSA

Answer 4

c

Question 5

Addition of 2% NaCl in MHA is used for AST of what organism? a. Streptococcus b. Haemophilus c. S. aureus d. Enterococcus

Answer 5

c

Question 6

Addition of 5% sheep’s blood in MHA is used for AST of what? a. S. aureus b. Streptococcus c. Haemophilus sp. d. Pseudomonas

Answer 6

b

Question 7

HTM with X and V factor is used for AST of what organism? a. Streptococcus b. Staphylococcus c. Haemophilus sp. d. Enterococcus

Answer 7

c

Question 8

Maximum allowed calcium concentration in MHA? a. 50 mg/L b. 25 mg/L c. 12.5 mg/L d. 5 mg/L

Answer 8

b

Question 9

Maximum allowed magnesium concentration in MHA? a. 25 mg/L b. 20 mg/L c. 15 mg/L d. 12.5 mg/L

Answer 9

d

Question 10

Increased Ca and Mg concentration decreases activity of aminoglycosides against what? a. All microorganisms b. Streptococcus c. Pseudomonas aeruginosa d. S. aureus

Answer 10

c

Question 11

Increased Ca and Mg concentration decreases activity of tetracyclines against what? a. Gram positives only b. Gram negatives only c. All microorganisms d. Fungi

Answer 11

c

Question 12

Thymidine content in Kirby Bauer media should be? a. High b. Moderate c. Minimal to absent to completely absent d. Variable

Answer 12

c

Question 13

Excess thymidine can result in false resistance to which drugs? a. Aminoglycosides b. Sulfonamides and trimethoprim c. Tetracyclines d. Beta lactams

Answer 13

b

Question 14

Standard pH of MHA for AST? a. 6.0–6.5 b. 6.8–7.0 c. 7.2–7.4 d. 7.5–8.0

Answer 14

c

Question 15

Most pathogens are described as what type regarding pH? a. Acidophilic b. Alkaliphilic c. Neutrophil d. Halophilic

Answer 15

c

Question 16

Decreased pH results in decreased activity of which drugs? a. Tetracyclines b. Aminoglycosides erythromycin clindamycin c. Sulfonamides d. Penicillin

Answer 16

b

Question 17

Decreased pH results in increased activity of what? a. Aminoglycosides b. Macrolides c. Tetracyclines d. Beta lactams

Answer 17

c

Question 18

Standard agar depth for disk diffusion? a. 2–3 mm b. 3–5 mm c. 5–7 mm d. 7–10 mm

Answer 18

b

Question 19

Agar depth less than 3 mm results in what? a. False resistance b. False susceptibility c. No growth d. Smaller zones

Answer 19

b

Question 20

Agar depth more than 5 mm results in what? a. False susceptibility b. Accurate results c. False resistance d. Larger zones

Answer 20

c

Question 21

Standard incubation atmosphere? a. CO₂ enriched b. Anaerobic c. Humidified ambient air d. Microaerophilic

Answer 21

c

Question 22

Excess CO₂ incubation causes what pH change? a. Increased pH b. No change c. Decreases pH d. Alkaline shift

Answer 22

c

Question 23

Excess CO₂ leads to decreased activity of which drugs? a. Tetracyclines only b. Aminoglycosides erythromycin clindamycin c. Sulfonamides d. Beta lactams

Answer 23

b

Question 24

Excess CO₂ leads to increased activity of what? a. Aminoglycosides b. Macrolides c. Tetracyclines d. Penicillin

Answer 24

c

Question 25

Strict incubation temperature for Kirby Bauer? a. 30°C b. 35°C c. 37°C d. 42°C

Answer 25

b

Question 26

Incubation above 35°C may cause failure to detect what? a. VRE b. ESBL c. MRSA d. CRE

Answer 26

c

Question 27

Standard incubation length for disk diffusion? a. 12–14 hours b. 14–16 hours c. 16–18 hours d. 18–24 hours

Answer 27

c

Question 28

Long term storage of antibiotic disks? a. Room temperature b. 4°C c. Non-frost freezer at -20°C (tightly sealed desiccated container) d. -80°C freezer

Answer 28

c

Question 29

Short term storage of antibiotic disks? a. Room temperature b. 2–8°C (tightly sealed desiccated container) c. -20°C d. 37°C

Answer 29

b

Question 30

Before opening disk container what should be done? a. Shake container b. Freeze container c. Allow to warm at RT before opening container d. Add desiccant

Answer 30

c