Chapter 42- Antimicrobial Sensitivity Testing

Question 1

-One of the worlds most pressing public and animal health problems
-Occurs when a microbe changes or mutates in some way that reduces or eliminates the effectiveness of drugs, chemicals, or other agents designed to cure or prevent infections

Answer 1

Antibiotic resistance

Question 2

Why does antibiotic resistance happen?

Answer 2

when antibiotics are used to kill or inhibit the growth of susceptible bacteria, sometimes one of the bacteria survives

Question 3

Antibiotic resistance can also occur through

Answer 3

mutation of their genetic material or by acquiring pieces of DNA that code for the resistance properties

Question 4

Antibiotic resistant bacteria can quickly spread to

Answer 4

other mammals and threaten communities w/ a new strain of infectious disease that is hard to cure

Question 5

The most common mutation and form of antimicrobial resistance involves

Answer 5

extended-spectrum beta-lactamase (ESBL)

Question 6

Beta-lactamases aka

Answer 6

penicillinase

Question 7

ESBLs can cause

Answer 7

serious infection and are a common source of nosocomial infection

Question 8

Once a bacteria has been isolated from a patient, _ _ testing can be performed to determine the susceptibility or resistance to specific antimicrobial drugs

Answer 8

antimicrobial testing

Question 9

For an antimicrobial sensitivity test, the sample must be collected BEFORE

Answer 9

any tx begins

Question 10

-Most preferred method
-Uses paper discs impregnated with antimicrobial
-Quantitive and requires the measurement of inhibitory zone sizes

Answer 10

agar diffusion method

Question 11

Agar diffusion method techniques

Answer 11

Modified Kirby-Bauer technique or standardized disk susceptibility method (most used), U.S. Food & Drug administration method, International collaborative disc technique

Question 12

Antimicrobial discs should be kept in the _ and _ should not be used

Answer 12

refrigerator; outdated

Question 13

Indirect sensitivity testing requires that colony samples be taken from

Answer 13

a culture plate, subcultured in broth media, and incubated to achieve turbidity to match a standardized 0.5 McFarland suspension

Question 14

Direct testing method

Answer 14

application of undiluted samples (ex: urine) directly to a Mueller-Hinton plate

Question 15

Indirect testing is more _ than direct testing but results are not available as quickly

Answer 15

precise

Question 16

Discs should be placed

Answer 16

10-15mm part and avoid overlapping of Zones of Inhibition (ZOI)

Question 17

ZOI measured using a

Answer 17

caliper transparent ruler or template and includes the antibiotic disc

Question 18

Measurement is compared to a chart of ZOI for each antibiotic to determine the

Answer 18

relative resistance of the bacterium to the antimicrobial

Question 19

The zone sizes are divided into two major categories

Answer 19

resistant or susceptible

Question 20

Intermediate susceptibility

Answer 20

drug may be used for systemic infection if a high dosage is safe

Question 21

Strains of staphylococci are resistant to

Answer 21

methicillin and other similar drugs

Question 22

Minimum inhibitory concentration (MIC) of an antimicrobial is

Answer 22

the lowest concentration of a specific antimicrobial that can inhibit the growth of a given bacteria

Question 23

Choice of a specific concentration of antimicrobial is based on the

Answer 23

MIC, site of infection, and breakpoint of the antimicrobial (the dilution of the antimicrobial at which the bacteria begins to show resistance)

Question 24

MIC methods

Answer 24

agar diffusion or Microwell

Question 25

The presence of pathogenic bacteria does not necessarily indicate

Answer 25

infection

Question 26

Colony counts on cultured urine can help support a diagnoses of

Answer 26

UTI

Question 27

_ samples are not recommended for a colony count

Answer 27

Voided