Question
A. Altered penicillin-binding proteins
B. Drug efflux
C. Breaks drug structure
D. Alteration in 50S ribosome structure
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Correct Answer » C Explanation |
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Ans: C. Breaks drug structure
β-lactamases are produced by staphylococci, Haemophilus, 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.
