L12 - Antibiotic Resistance

Question 1

Why is Antibiotic resistance a global concern?

Answer 1

25,000 poeple die a year

Antibiotic resistance:

Increases mortality

challenges control of infectious diseases

threatens a return to the pre-antibiotic era

increases the costs of health care

jeopardizes health-care gains to society

Question 2

State the different mechanisms of antibiotic resistance?

Answer 2

Drug inactivation
e.g. beta-lactamase

Metabolic by-pass
e.g. vancomycin
D-ala-D-lac

Efflux pump

Overproduction
of target

Intrinsic
impermeability

Altered or new target

Question 3

What are some genetic mechanisms by which bacteria can become resistant?

Answer 3

Chromosome-mediated
Due to spontaneous mutation: 
in the target molecule 
in the drug uptake system
Mutants are SELECTED; they  are NOT induced

Plasmid-mediated gene exchange
Common in Gram-negative bacteria
Transferred via conjugation
Multidrug resistance

Question 4

How does gene transfer in bacteria occur?

Answer 4

transformation:
Bacteria can take up DNA from its environment and other bacterial cells and incorporate it into its own genome

transduction:
fragment of DNA from another bacterial cell which was a former phage host can be passed on

Conjugation:
2 organisms come together, conjugal tube is formed which allows the genetic exchange from donor bacteria to the recipient bacteria

Question 5

How does resistance to beta lactams occur in both gram positive and negative bacteria?

Answer 5

Gram + ve

ß-lactamase (Penicillinase)

Alteration of the transpeptidase enzyme
(PBP)

Gram - ve

ß -Lactamase (Penicillinase)

Alteration of porins