Medical Microbiology: Bacterial Resistance Mechanisms Encounterd In Clinical Practice

Front 1

What percent of antibiotics used in the US are used inappropriately?

Back 1

50%

Front 2

General Mechanisms of Resistance:

Back 2

1. Enzyme inactivation or modification of antimicrobial agent (ex. b lactamases and AMEs)

2. Decreased uptake (efflux pumps) of antimicrobials (seen in Gram - bacteria)

3. Altered target site (PBPs)

4. Alternative pathways around antimicrobial activity (seen with trimethoprim)

Front 3

Intrinsic resistance

Back 3

I think of it as innate resistance, which results from normal genetics or physiologic state of microorganism. Referred to as nature of the beast...

Front 4

Acquired resistance

Back 4

Resistance acquired by mutation within a genome or by genetic transfer from other strains of bacteria. The bacteria have altered cellular physiology and structure caused by changes in the genetic makeup.

Front 5

Plasmid

Back 5

Circular extrachromosomal DNA naturally present in bacteria

Front 6

Transposon

Back 6

Genes that move from 1 DNA molecule to another within the same site

Front 7

Common B lactamases

Back 7

TEM-1 and SHV -1

Front 8

Organisms effected by common Beta lactamases:

Back 8

Staph, Enterococci,
Gram - bacteria: enterobacteriaceae, P. aeruginosa and Acinetobacter

Front 9

What does a Gram negative bacteria have that Gram positive lack?

Back 9

Periplasmic space where there is a higher concentration of beta lactamase. This is why gram negative bacteria are more resistant to antimicrobials then Gram + bacteria.

Front 10

Nafcillin and oxacillin are special because they avoid hydrolysis by Beta lactamase, why is this?

Back 10

They have side chains that are modified to reduce hydrolysis of the Beta lactam ring.

Front 11

AMP C is basically another name for what enzyme?

Back 11

Beta lactamases or cephalosporinases

Front 12

Induction is also known as reversible what?

Back 12

Reversible Derepression

Front 13

Labile antibiotic

Back 13

In this case, an antibiotic would be inactived by the enzymes produced by the bacteria