Notes on Classification of Penicillin’s, MCQ on Antibiotics, Spectrum and Features

Classification of Penicillins

Class	Examples	Spectrum / Features
Natural Penicillins	Penicillin G (IV), Penicillin V (oral)	Narrow spectrum – mainly Gram-positive cocci, anaerobes, spirochetes (e.g., Treponema)
Penicillinase-Resistant Penicillins	Methicillin, Nafcillin, Oxacillin, Cloxacillin	Resistant to staphylococcal beta-lactamase; used for MSSA
Aminopenicillins	Amoxicillin, Ampicillin	Extended spectrum – includes some Gram-negative (e.g., E. coli, H. influenzae)
Carboxypenicillins	Ticarcillin, Carbenicillin	Extended Gram-negative coverage (e.g., Pseudomonas); less used now
Ureidopenicillins	Piperacillin	Broad spectrum – strong anti-pseudomonal activity; often combined with tazobactam
Beta-lactam/Beta-lactamase Inhibitor Combos	Amoxicillin + Clavulanic acid, Piperacillin + Tazobactam	Effective against beta-lactamase producing organisms

Which of the following is a natural penicillin?
A. Amoxicillin
B. Penicillin G
C. Oxacillin
D. Piperacillin
Answer: B. Penicillin G
Which penicillin is resistant to beta-lactamase produced by Staphylococcus aureus?
A. Ampicillin
B. Penicillin V
C. Cloxacillin
D. Ticarcillin
Answer: C. Cloxacillin
Which class of penicillins is effective against Pseudomonas aeruginosa?
A. Natural penicillins
B. Aminopenicillins
C. Ureidopenicillins
D. Penicillinase-resistant penicillins
Answer: C. Ureidopenicillins
Which of the following combinations is used to overcome beta-lactamase resistance?
A. Ampicillin + Sulbactam
B. Amoxicillin + Cephalexin
C. Piperacillin + Gentamicin
D. Methicillin + Clavulanic acid
Answer: A. Ampicillin + Sulbactam
Amoxicillin belongs to which class of penicillins?
A. Natural penicillins
B. Carboxypenicillins
C. Aminopenicillins
D. Ureidopenicillins
Answer: C. Aminopenicillins