Bacterial Resistance

What are the two types of antimicrobial resistance?

Intrinsic and acquired

Define intrinsic resistance

Antimicrobial agent NEVER had activity against bacteria

Define acquired resistance

Antimicrobial was originally active, but genetic makeup of the bacteria has changed so the antimicrobial is no longer effective

What are the four mechanisms of acquired resistance?

1. Enzymatic inactivation

2. Efflux pumps

3. Changing in antibiotic binding site

4. Change in permeability

How are antimicrobial-resistant strains selected for?

When colonizing or infecting bacteria are exposed to antibiotics

What cell structure can cause decreased permeability through the cell membrane?

Porin channels

Define porin channels

Channels or tunnels that allow the antibiotic to enter the bacterial cell

Describe mutations in porin channels

Mutations can be present that will inhibit the antibiotic from being able to travel through them

Define efflux pumps

Allows the antibiotic to enter the bacterial cell and then pump it back out of the cell

Like a decoy method

Describe target alteration/binding site modifications in PBP that lead to MRSA

Beta-lactams bind to PBP 2 in MSSA

When the mecA gene is present, this causes a conformational change from PBP 2 to PBP 2a, leading to MRSA

Beta-lactam antibiotics cannot bind to PBP 2a

What is a major mechanism of bacterial resistance for beta-lactams and aminoglycosides?

Antibiotic degrading enzymes

What antibiotic degrading enzyme works against beta-lactams?

Beta-lactamases

In which type of bacteria are beta-lactamases more potent?

In Gram negative bacteria

What beta-lactamases confer resistance to ceftriaxone?

Extended-spectrum beta-lactamases (ESBL)