Module -> Antibiotic Testing & Resistance

Antibiotic Testing & Resistance

Antimicrobial Susceptibility Testing (AST)

Testing used to determine which antimicrobial is effective against a bacterial isolate.

Kirby-Bauer Test

A disk diffusion test that measures the zone of inhibition around antibiotic disks.

Zone of Inhibition

The area around an antibiotic disk where bacterial growth is prevented.

Broth Dilution

A test using different antibiotic concentrations to determine the MIC.

MIC

Minimum Inhibitory Concentration; the lowest drug concentration that prevents visible bacterial growth.

E-Test

A test combining diffusion and dilution methods to determine antibiotic susceptibility.

Low MIC

Generally means less drug is needed to inhibit the organism, but MIC must be interpreted for the drug, host, infection site, and bacteria.

Sub-MIC

An antibiotic concentration below the MIC that can favor selection of resistant bacteria.

Combination Antibiotic Therapy

Using more than one antimicrobial to improve treatment or reduce resistance.

Synergy

When two drugs work together more effectively than either alone.

Polymicrobial Infection

An infection caused by multiple types of microorganisms.

Four-Quadrant Therapy

Therapy designed to cover Gram-positive, Gram-negative, aerobic, and anaerobic bacteria.

Intrinsic Resistance

Resistance that bacteria naturally possess because of their genetics or structure.

Acquired Resistance

Resistance that develops through mutation or horizontal gene transfer.

Resistance Mechanism 1

Preventing the antibiotic from entering the bacterial cell.

Resistance Mechanism 2

Pumping the antibiotic out of the bacterial cell using efflux pumps.

Resistance Mechanism 3

Using enzymes to destroy or modify the antibiotic.

Resistance Mechanism 4

Changing or protecting the antibiotic's target site.

VRE

Vancomycin-resistant Enterococcus.

MRSA

Methicillin-resistant Staphylococcus aureus.

MRSP

Methicillin-resistant Staphylococcus pseudintermedius.

ESBL

Extended-spectrum beta-lactamase-producing bacteria such as E. coli and Klebsiella.

MDR

Multidrug-resistant bacteria.

XDR

Extensively drug-resistant bacteria.

Antimicrobial Stewardship

Responsible use of antimicrobials to preserve their effect