NEET PG Medical – 2020 – Question -58
Mechanism of resistance to penicillin’s via beta-lactamase is
a) Altered penicillin-binding proteins
b) Drug efflux
c) Breaks drug structure
d) Alteration in 50S ribosome structure
Correct Answer – C
Ans: C. Breaks drug structure
β-lactamases are produced by staphylococci, Herophilus, gonococci, etc. which inactivate penicillin G.
The β-lactamases may be present in low quantity but strategically located Periplasmically (as in gram-negative bacteria) so that the drug is inactivated soon after entry, or maybe elaborated in large quantities (by gram-positive bacteria) to diffuse into the medium and destroy the drug before entry.
Beta-lactam antibiotics share the structural feature of a beta-lactam ring.
This feature is responsible for the inhibition of bacterial cell wall synthesis.
The target molecules are peptidoglycan cross-linking enzymes (e.g. transpeptidases and carboxypeptidases) which can bind beta-lactam antibiotics (penicillin-binding proteins, PBP).
Bacterial cell death is initiated by beta-lactam antibiotic-triggered release of autolytic enzymes.
In contrast to gram-positive bacteria (absence of an outer membrane), the antibiotic has to penetrate through porins of the outer membrane of gram-negative bacteria before touching PBP’s.
Bacterial resistance to beta-lactam antibiotics includes modification of porins (permeability barrier) and of targets (low affinity of PBP’s for the drug), production of inactivating enzymes (beta-lactamases) and inhibition of release of autolytic enzymes.
Ref: K. D. Tripathi 7th Edition. Page. 717 – 720
ncbi.nlm.nih.gov/pubmed/8314292
