Antibiotic Resistance

Question 1

What is intrinsic resistance?

Answer 1

Intrinsic resistance is a quality that a bacteria naturally has to prevent the drug from penetrating or acting on it
- Lack of drug targets or lack of access to drug targets

Question 2

What is acquired resistance?

Answer 2

Genetic variability allows bacteria to become resistant to an antibiotic that used it to be sensitive to

Question 3

What is constitutive resistance?

Answer 3

Bacterial mechanism is consistently present and usually essential to bacterial function

Question 4

What is inducible resistance?

Answer 4

Resistance gene turned on in response to environmental stimuli (e.g. antibiotics) => Expanded-spectrum beta-lactamases in E. coli

Question 5

What are examples of single nucleotide base pair mutations?

Answer 5

1) Quinolone resistance:
- Point-mutations in DNA gyrase or topoisomerase
2) Evolution of beta-lactamases in gram-negatives
- Families differ by many AA’s. Within families, isoenzymes differ from each other by single or several AA’s.

Question 6

What is the mechanism behind larger DNA rearrangement (jumping genes) bacterial resistance?

Answer 6

Transposable DNA segments prone to rearrangement in bacterial chromosome or plasmid DNA

Question 7

What is the mechanism behind acquisition of DNA from other bacteria as a means of bacterial resistance?

Answer 7

• Foreign DNA containing resistance genes can be acquired from plasmids, bacteriophages, and transposable genetic elements
• Conjugation, transduction, transformation allow genetic material to move within populations of bacteria and is perpetuated over time

Question 8

How do bacteria survive antibiotic exposure?

Answer 8

1) Alter drug permeability
2) Alter drug targets
3) Inactivate of drug
4) Active efflux

Question 9

What are the dominant resistance mechanisms to cell wall synthesis blocking antibiotics?

Answer 9

1) Altered penicillin-binding proteins (ie Streo Pneumonia)

2) Modified cell wall targets (Vancomycin resistant enterococcus)

Question 10

What is the major resistance mechanism to quinolines?

Answer 10

1) Altered gyrase or topoisomerases

Question 11

What are the major resistance issues of S. aureus?

Answer 11

1) Beta-lactamase

2) Altered PBPs (MRSA, mecA gene+)

Question 12

What drug should be used for resistance S. aureus?

Answer 12

Vancomycin

Question 13

What are the major resistance issues of Strep. pneumonia?

Answer 13

Altered PBPs

Question 14

What drugs should be used for resistant Strep. pneumoniae?

Answer 14

1) Meningitis or Sepsis: Vancomycin/Ceftriaxone

2) Pneumonia: Ceftriaxone

Question 15

What is the major resistance issue of Group A strep?

Answer 15

Erythromycin resistance

Question 16

What drugs should be used for resistant Group A Strep?

Answer 16

Penicillin or cefazolin

Question 17

What are the major resistance issues of N. meningitides?

Answer 17

• Beta-lactamase

- Altered PBPs

Question 18

What drugs should be used for resistant N. meningitides?

Answer 18

Ceftriaxone

Question 19

What are the major resistance issues of H. influenzae?

Answer 19

Beta-lactamase production

Question 20

What drugs should be used for resistant H. influenzae?

Answer 20

Ceftriaxone or beta-lactam + beta-lactamase inhibitor combinations

Question 21

What are 3 main ways of managing MRSA infections?

Answer 21

1) Incision and drainage
2) Use of cultures
3) Foreign body/device removal (if in place >30 days)

Question 22

What are the common gram negative rods that carry a lot of drug resistance?

Answer 22

1) Enterobacteriaceae => E. coli, Klebsiella, Enterobacter, (Serratia, Proteus, Citrobacter, Salmonella)
2) Acinetobacter
3) Pseudomonas

Question 23

What risks are associated with gram negative rod resistance?

Answer 23

> Hospital stay, ICU, longterm care facility, central lines and urinary catheters, abdominal surgery, prior antibiotics, ventilator, dialysis

Question 24

Gram negative rods generally carry resistance to which drug group?

Answer 24

Beta lactams (Penicillinase and Cephalosporinases, Carbapenemases)

Question 25

What populations are at increased risk of multi drug resistant acinetobacter?

Answer 25

1) Health-cares associated infections:
- Mostly VAP and bloodstream infections
- Common source outbreaks related to respiratory and ventilator equipment
2) Military personnel
3) Disasters
4) Community outbreaks