This document discusses the history and classification of antibacterial agents. It begins by defining an antibacterial as an agent that interferes with bacterial growth and reproduction. It then provides a brief history of antibacterial use dating back to ancient Egypt and Greece. The document outlines several important discoveries and individuals that advanced the field, such as Alexander Fleming, Florey, Chain, and Selman Waksman. It proceeds to classify antibacterials according to their spectrum of activity (broad vs narrow), effect on bacteria (bactericidal vs bacteriostatic), and mode of action (inhibiting cell wall, membrane, protein, nucleic acid synthesis etc.). The classifications and examples are described in detail in the document.

1. MIDHUN M..NAIR,
FIRST SEMESTER Msc
SCHOOL of ENVIRONMENTAL
SCIENCE ,
MG UNIVERSITY KOTTAYAM

2. ANTIBACTERIALS ????
• An antibacterial’s is an agent that interferes
with the growth and reproduction of bacteria.
• Antibacterial are now most commonly
described as agents used to disinfect surfaces
and eliminate potentially harmful bacteria

3. • Charaka Samhitha&Astangahrydya
indicate the power of plant syrup

4. • In And Greece, old moldy bread was pressed
against wounds to prevent infection
• Around 1550 B.C., Egyptians used honey for
dressing wounds.
• The Eber’s papyrus(1550 B.C), It contains a list
of formulas and remedies to cure illnesses.

5. The Pre-Antibacterial Era
• pyocyanase-The first recorded microbial by-
product (Pseudomonas aeruginosa)
• observed by E. de Freudenreich (Germany) in
1888.
• Paul Ehrlich, “magic bullet” that could
selectively kill microorganisms.

6. • Salvarsan - the first chemical compound
shown to cure a human disease, syphilis.
• Arsphenamine chemical dye they referred to
as compound 606 and later named Salvarsan

7. The Golden Age of Antibacterials
• Alexander Fleming
• Florey and Chain:when its applicability as a
therapeutic agent was made possible

8. • Gerhard Domagk
• Discovered and developed the first
sulfonamide, (Prontosil, the first commercially
available antibacterial.)

9. • Selman Waksman:the Father of Antibiotics
• discovered by streptomycin in 1944

12. CLASSIFICATION OF
ANTIBACTERIAL AGENTS
Antimicrobials are classified in several ways
• spectrum of activity
• effect on bacteria
• mode of action

13. ACCORDING TO SPECTRUM
OF ACTIVITY
• Broad spectrum antibacterials:-are active
against both Gram-positive and Gram-
negative organisms
Examples : tetracyclines, phenicols,
fluoroquinolones, “third-generation” and
“fourth-generation” cephalosporins

14. • Narrow spectrum antibacterials:- have limited
activity and are primarily only useful against
particular species of microorganisms
Examples
-Glycopeptides and Bacitracin are only
effective against Gram-positive bacteria
-Polymixins are usually only effective against
Gram negative bacteria
- Aminoglycosides and Sulfonamides are only
effective against aerobic organisms
- Nitroimidazoles are generally only effective for
anaerobes.

15. Effect on Bacteria
• Bactericidal drugs are those that kill target
organisms.
• Examples of bactericidal drugs include
aminoglycosides, cephalosporins, penicillins, and
quinolones.
• Bacteriostatic drugs inhibit or delay bacterial
growth and replication.
• Examples of such include tetracyclines,
sulfonamides, and macrolides.
• both bacteriostatic and bactericidal

16. Mode of Action
• Different antibiotics have different modes of
action
• Owing to the nature of their structure and
degree of affinity to certain target sites
within bacterial cells

17. 1.Inhibitors of cell wall synthesis
• Cell wall is critical for the life and survival of
bacterial species
• A drug that targets cell walls can therefore
selectively kill or inhibit bacterial organisms
• Examples: penicllins, cephalosporins,
bacitracin and vancomycin.

18. 2.Inhibitors of cell membrane function
• A disruption or damage to cell membrane
could result in leakage of important solutes
essential for the cell’s survival.
• The action of this class of antibiotic are often
poorly selective and can often be toxic for
systemic use in the mammalian host
• Most clinical usage is therefore limited to
topical applications.
• Examples: polymixin B and colistin

19. 3.Inhibitors of protein synthesis
• Enzymes and cellular structures are primarily made of
proteins.
• Protein synthesis is an essential process necessary for
the multiplication and survival of all bacterial cells.
• Several types of antibacterial agents target bacterial
protein synthesis by binding to either the 30S or 50S
subunits of the intracellular ribosomes.
• This activity then results in the disruption of the
normal cellular metabolism of the bacteria, and
consequently leads to the death of the organism or the
inhibition of its growth and multiplication.
• Examples: Aminoglycosides, macrolides, lincosamides,
streptogramins, chloramphenicol, tetracyclines.

20. 4.Inhibitors of nucleic acid synthesis
• DNA and RNA are keys to the replication of all
living forms, including bacteria.
• Some antibiotics work by binding to
components involved in the process of DNA or
RNA synthesis, which causes interference of
the normal cellular processes which will
ultimately compromise bacterial
multiplication and survival.
• Examples: quinolones, metronidazole, and
rifampin.

21. 5.Inhibitors of other metabolic processes.
• Other antibiotics act on selected cellular
processes essential for the survival of the
bacterial pathogens.
• For example, both sulfonamides and
trimethoprim disrupt the folic acid pathway,
which is a necessary step for bacteria to produce
precursors important for DNA synthesis.
• Sulfonamides target and bind to dihydropteroate
synthase, trimethophrim inhibit dihydrofolate
reductase;
• both of these enzymes are essential for the
production of folic acid, a vitamin synthesized by
bacteria, but not humans.

23. PROPERTIES OF ANTIBACTERIALS

27. in
“In wine there is wisdom,in beer
there is freedom,in water there is
bacteria”