1) Antibiotics are chemotherapeutic agents produced by microorganisms that suppress or kill other microorganisms. They work by exploiting biochemical differences between microbial and human cells. 2) Paul Ehrlich is considered the founder of chemotherapy for treating diseases like syphilis with synthesized chemical compounds in 1909. 3) There are several ways to classify antibiotics, including by their microbial source or target, mechanism of action, spectrum of activity, chemical structure, or effect on microbes.

1. Antibiotics
Definition, Classes etc.

2. Antibiotics, Chemotherapeutic
agents, anti-infective drugs,
antimicrobial drugs
• Obtained from other microorganisms e.g. bacteria,
fungi etc.
OR
• Produced/derived from microorganisms used to
suppress the growth or to kill the other
microorganisms
NOTE: All antibiotics are chemotherapeutic agents but not all
chemotherapeutic agents are antibiotics.

3. Principle/Base of chemotherapy
• Known as “concept of selective toxicity”.
• Proposed by a scientist “Paul Ehrlich” in 1909. He is now
a days considered as “founder of chemotherapy”.
• For the first time, he treated STD i.e. “syphilis” caused by
“Treponema pallidum” by using “arsphenamine” or
(salvarsan ℞).
• Biochemical difference between microbial cells and
human cells provided base for chemotherapy.

4. Classes of antibiotics
1. Type (1) Nature of microbes/microorganisms
2. Type (2) Mechanism of action
3. Type (3) Nature of spectrum
4. Type (4) Chemistry/chemical structure
5. Type (5) Nature of action
6. Type (6) Source

5. Type (1) Nature of
microbe/microorganisms
a. Antibacterial therapy
b. Antifungal therapy
c. Antiviral therapy
d. Antiparasitic therapy
i. Antimalarial drugs
ii. Antiamoebic drugs
e. Antihelminths/ anthelmintic therapy

6. Type (2) Mechanism of action
a. Cell wall synthesis inhibitors
b. Cell membrane disruptor
c. Protein synthesis inhibitors
d. Folic acid synthesis inhibitors/ folate antagonists
e. DNA, Nucleic acid synthesis/function inbitors

7. a. Cell wall synthesis inhibitors
BC
• Beta lactam drugs.
• Caspofungins

8. b. Cell membrane disruptor
APP
• Azole drugs
• Polyene drugs
• Polymyxin B

9. c. Protein synthesis inhibitors
• 30s ribosomal subunit
inhibitor:
AT
• Aminoglycosides
• Tetracyclins
• 50s ribosomal subunit inhibitor:
LCM LS
• Lincosamides
• Chloramphenicol
• Macrolides
• Linezolid
• Streptogramin

10. d. Folic acid synthesis
inhibitor/folate antagonist
PTS
• Pyrimethamine
• Trimethoprim
• Sulphonamides

11. e. DNA, Nucleic acid
synthesis/function Inhibitors
• Flouroquinolones
• Quinolones
• Anti malarial
• Anti TB
• Anti parasitic

12. Type (3) Nature of spectrum
a. Very narrow spectrum
b. Narrow spectrum
c. Extended Spectrum

13. a. Very Narrow Spectrum
• Penicillinases
• Anti staphyloccal drugs

14. b. Narrow Spectrum
• Penicillin G (Benzyl Penicillin)

15. c. Extended Spectrum
• Wide Spectrum:
ACA
• Ampicillin
• Clarithromycin
• Azithromycin
• Broad Spectrum:
TC
• Tetracycline
• Chloramphenicol

16. Type (4) Chemistry/
Chemical Structure
1. ß-lactam antibiotics e.g. penicillin,
cephalosporin, carbopenems, monobactam

17. 2. Sulphonamindes
e.g.
Sulfacetamide,
sulfadoxine etc.

18. 3. Tetracyclines e.g.
Oxytetracyclines,
Rolitetracyclines etc.

19. 4. Nitrobenzene derivatives e.g.
Chloramphenicol etc.

20. 5. Macrolide e.g.
Erythromycin,
clarithromycin etc.

21. 6. Polyene antibiotics
e.g.
Nystatin,
amphotericin B etc.

22. 7. Azole antibiotics
e.g.
Diazole (Clotrimazole,
Metronidazole),
Triazole etc.

23. 8. Polypeptides e.g. Polymyxin B
9. Glycopeptides e.g. vancomycin

24. Type (5) Nature of action
a. Microbiostatic
b. Microbicidal

25. a. Microbistatic
• Bacteriostatic:
TCS
• Tetracyclines
• Chloramphenicol
• Sulphonamides
• Fungistatic:
AG
• Azole drugs
• Griseofulvin

26. b. Microbicidal
• Bactericidal:
FB
• Fluoroquinolones
• Beta lactam drugs
• Fungicidal:
• Amphotericin B

27. Type (6) Source
a. Microbiological origin
b. Semisynthetic
c. Synthetic

28. a. Microbiological origin
• Fungi:
• E.g. Penicillium species
• Bacteria:
• E.g. Bacillus species
(Bacitracin)
• Soil:
• Streptomycetes,
actinomycetes e.g.
TMC
• Tetracyclines
• Macrolides
• Chloramphenicol

29. b. Semi Synthetic
AC
• Aminopenicillin (amoxicillin)
• Cephalosporins (Ceftriaxone)

30. c. Synthetic
SF
• Sulphonamides (co trimoxazole)
• Fluoroquinolones (Ciprofloxacin)
• Certain anti TB
• Certain Antimalarial