Antibiotics Notes – Complete Study Guide with Mnemonics & Quick Revision

Prepared By

Anish Mandal

, Introduction to Antibiotics
What are Antibiotics?
Antibiotics are drugs used to kill or stop the growth of bacteria.
They are used to treat bacterial infections in humans and animals.

They can be natural (from microorganisms), semi-synthetic, or synthetic
They do not work against viruses (like cold or flu)

Bactericidal vs Bacteriostatic
Bactericidal Antibiotics

These antibiotics kill bacteria directly.

Cause bacterial cell death
Useful in serious infections (e.g., sepsis)
Examples: Penicillins, Cephalosporins, Aminoglycosides

Bacteriostatic Antibiotics

These antibiotics stop the growth of bacteria but do not kill them directly.

Bacteria are eliminated by the immune system
Used in mild to moderate infections
Examples: Tetracyclines, Macrolides, Sulfonamides

Spectrum of Activity
Broad-Spectrum Antibiotics

These antibiotics act against a wide range of bacteria (both Gram-positive
and Gram-negative).

Useful when the exact bacteria is unknown
May disturb normal flora
Examples: Tetracyclines, Chloramphenicol

Narrow-Spectrum Antibiotics

These antibiotics act against specific types of bacteria.

, More targeted therapy
Less effect on normal flora
Examples: Penicillin G, Vancomycin


Classification of Antibiotics
Class Examples Spectrum

Beta-lactams Penicillin G, Mainly Gram (+),
(Penicillins & Amoxicillin, some Gram (−)
Cephalosporins) Ampicillin,
Ceftriaxone,
Cefepime,
Cephalexin

Macrolides Azithromycin, Gram (+) & some
Erythromycin, Gram (−)
Clarithromycin

Tetracyclines Tetracycline, Broad-spectrum
Doxycycline

Aminoglycosides Gentamicin, Mainly Gram (−)
Streptomycin,
Amikacin

Fluoroquinolones Ciprofloxacin, Broad (Gram + &
Levofloxacin −)

Sulfonamides Sulfamethoxazole, Broad-spectrum
Sulfadiazine

Glycopeptides Vancomycin, Gram (+) only
Teicoplanin