2. Antimicrobial agents :
• An antimicrobial agent is defined as a natural or synthetic substance that kills or
inhibits the growth of microorganisms such as bacteria, fungi and algae.
Antibiotics – ‘anti’, meaning ‘against’, and ‘biotikos’, meaning ‘concerning life’.
• These are substances produced by microorganisms, which selectively suppress
the growth of or kill other microorganisms at very low concentrations.
Note: All antibiotics are antimicrobials but all antimicrobials are not antibiotics
3. Antibiotic vs Antimicrobial:
Antibiotic
• It is a term used to describe a
compound that is used to
combat bacterial infections
inside the body. "
Antimicrobial
It is a greater encompassing
term for any additive that
inhibits or kills a multitude
of microorganisms, both inside
and/or outside of the body.
4. Chemotherapeutic agents
• Drugs in this class differ from all others
• Designed to inhibit/kill the infecting organism and have no/minimal
effect on the recipient.
• ‘Treatment of systemic infections with specific drugs that selectively
suppress/kill the infecting microorganism without significantly
affecting the host.’
5. The basis of selective microbial toxicity is -
1. The action of the drug on a component of the microbe (e.g.
bacterial cell wall).
2. Metabolic processes (e.g. Folate synthesis) that is not found in the
host.
3. High affinity for certain microbial biomolecules (e.g. Trimethoprim
for bacterial dihydrofolate reductase).
6. Gram positive vs Gram Negative
Gram positive bacteria
• Thick cell wall
• Peptidoglycan directly accessible
from environment
Gram negative bacteria
• Thin cell wall
• Surrounded by inner and outer
membrane of lipopolysaccharide,
phospholipids, and proteins
• Outer membrane is a barrier to
diffusion of antibiotics
• Limited antibiotics may diffuse
through porins
7.
8. CLASSIFICATION
Type of organisms against which primarily active
• 1. Antibacterial: Penicillins, Aminoglycosides, Erythromycin, Fluoroquinolones,
etc.
• 2. Antifungal: Griseofulvin, Amphotericin B, Ketoconazole, etc.
• 3. Antiviral: Acyclovir, Amantadine, Zidovudine, etc.
• 4. Antiprotozoal: Chloroquine, Pyrimethamine, Metronidazole, Diloxanide, etc.
• 5. Anthelmintic: Mebendazole, Pyrantel, Niclosamide, Diethyl carbamazine
9. Spectrum
1. Narrow
• Penicillin G
• Streptomycin
• Erythromycin
2. Broad
• Tetracycline
• Chloramphenicol
3. Extended
• Ampicillin
• Amoxicillin
• Most……..
Narrow spectrum antibiotics are active
against a selected group of bacterial types.
They can act on either gram +ve or gram –ve
but not both.
The broad spectrum antibiotics have an
antimicrobial spectrum which includes
some gram-positive and some gram-
negative organisms
Extended-spectrum are a group of semi-
synthetic antibiotics, because of their chemical
structure, have a wider spectrum of activity.
10. Bacteristatic Bactericidal
• Sulfonamides and Trimethoprim
• Tetracyclines
• Macrolides (Erythromycin)
• Chloramphenicol
• Ethambutol
• Nitrofurantoin
• Cotrimoxazol
• Penicillins
• Cephalosporins
• Aminoglycosides
• Vancomycin, Daptomycin
• Fluroquinolones (ciprofloxacin)
• INH, Rifampicin, Pyrazinamide
• Polymixins, Bacitracin
• Metronidazole
Some primarily static drugs may become cidal at higher concentrations (as attained in the urinary tract) & vice-
versa.
11. • 1. Sulfonamides and related drugs: Sulfadiazine and others, Sulfones—
Dapsone (DDS), Paraaminosalicylic acid (PAS).
• 2. Diaminopyrimidines: Trimethoprim, Pyrimethamine.
• 3. Quinolones: Nalidixic acid, Norfloxacin, Ciprofloxacin, Prulifloxacin, etc.
• 4. β-Lactam antibiotics:Penicillins, Cephalosporins, Monobactams,
Carbapenems.
• 5. Tetracyclines: Oxytetracycline, Doxycycline, etc.
Chemical Classification
