Final answer:
Vancomycin is the antibiotic utilized when there is resistance to penicillin and methicillin, effectively inhibiting cell wall synthesis in Gram-positive bacteria and serving as a treatment for serious infections like MRSA. The cell wall inhibiting drug used in cases of penicillin and methicillin resistance is Vancomycin (Option B).
Step-by-step explanation:
Penicillin derivatives, including Penicillin G and Methicillin, are known to combat bacterial infections by inhibiting bacterial cell wall synthesis. However, certain bacteria have developed resistance to these antibiotics through various mechanisms, such as the production of β-lactamases, which degrade the antibiotic. When such resistance occurs, an alternative treatment is necessary. Vancomycin, a glycopeptide antibiotic, is the drug of choice in situations where bacteria are resistant to penicillins.
It functions differently than β-lactam antibiotics by binding to the ends of peptide chains in cell wall precursors, which hinders the incorporation of these subunits into the peptidoglycan structure. This action obstructs both transglycosylation and transpeptidation processes essential for cell wall synthesis. As a result, vancomycin is bactericidal and especially effective against Gram-positive bacteria, which have a thick peptidoglycan layer and no outer membrane to impede vancomycin's access to the target sites.