Question

1.a. Methicillin (a Beta-lactamase resistant penicillin) resistance in Staphylococcus aureus results from which of the following mechanisms?

a. increased expression of drug efflux pumps

b. the acquisition and expression of a new type of penicillin binding protein

c. changes in D-ala-D-ala amino acids found in peptidoglycan

d. increased peptidoglycan biosynthesis

1.b. PBP2a confers resistance to beta-lactam antibiotics because it:

a. has a low affinity for nearly all beta-lactams

b. alters the D-ala-D-ala amino acids in peptidoglycan

c. degrades both penicillins and cephalosporins

d. alters the permeability of the outer membrane

Answer 1

Staphylococcus has more than one types of penicillin binding protein out of which PBP2A confers on bacteria methicillin resistance. It helps in cross-linking of cell wall made of peptidoglycan .

Answer 1) It changes in D Alanine -D Alanine amino acids in peptide part of peptidoglycan of cell wall. (Option c)

Answer 2) option (b) Alanine -Alanine part of peptidoglycan is altered so that antibiotic is rendered ineffective .