Page 90 - MNU-PM502- Pharmaeutical Microbiology Theoritical Book

Pharm D- Clinical Pharmacy Program Third Level Pharmaceutical Microbiology& Antimicrobials (PM 502)

Beta-lactam antibiotics

• A popular class of drugs, having a four‐membered lactam
ring called a beta -lactam ring

• They vary by side chain attached or additional cycles

Mechanism of Action

Inhibition of transpeptidases (penicillin-
binding proteins PBPs)

Inhibition of cross-linking

inhibiting the synthesis of the
peptidoglycan layer of bacterial cell

walls

Because cell walls are synthesized only in actively multiplying cells, the b-lactam
drugs are effective only against growing bacteria.

1- Penicillins

❑ Major source: Penicillium chrysogenum

❑ All penicillins are derived from 6-amino-
penicillanic acid

❑ All members of the family of penicillins share a
Common basic structure consisting of a thiazolidine ring connected to a
beta-lactam ring , which is attached to a side chain.

❑ Classification:

1- Natural penicillins
2- Antistaphylococcal penicillins
3- Aminopenicillins

4- Extended-spectrum penicillins

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