All of the following statements about penicillin-binding proteins are true EXCEPT:
Correct Answer: The MRSA have acquired a PBP which has very high affinity for Beta lactam antibiotics.
Description: PENICILLIN-G (BENZYLPENICILLIN)
Antibacterial spectrum PnG is a narrow spectrum antibiotic; activity is limited primarily to gram-positive bacteria and few others.
Bacterial resistance
Many bacteria are inherently insensitive to PnG because in them the target enzymes and PBPs are located deeper under lipoprotein barrier where PnG is unable to penetrate or have low affinity for PnG.
The primary mechanism of acquired resistance is the production of penicillinase.
Some resistant bacteria become penicillin tolerant and not penicillin destroying. Their target enzymes are altered to have low affinity for penicillin, e.g. highly resistant pneumococci isolated in some areas have altered PBPs.
The methicillin-resistant Staph. aureus (MRSA) has acquired a PBP which has a very low affinity for Beta-lactam antibiotics.
Some penicillin-resistant pneumococci and enterococci have altered PBPs.
The low-level penicillin-resistant gonococci are less permeable to the drug, while high degree resistant ones produce penicillinase, as do highly resistant H. influenzae. Both these appear to have acquired the penicillinase plasmid by conjugation or transduction and then propagated by selection.
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