this slide will deal with role of antibiotics in pathogenic organisms and also the resistant mechanism of such pathogenic bacteria against such available antibiotics which are now in use.

1. ANTIBIOTICS
B C MUTHU BHARATHI
I M.Sc., biotechnology

2. What is antibiotic?
• A microorganism to another microorganism
• Chemical substances
• Bacteria and fungi
Examples
vancomycin puromycin
penicillin chlorumphenicol

3. Classification
Natural antibiotics
from microorganisms
no structural or chemical modification
Eg. Penicillin G ( against gram positive bacteria)
Semisynthetic antibiotic
Chemical or structural modification
Eg. Modified semisynthetic pecinillin( against gram negative
too)

4. • Act on both gram positive
and gram negative
• Eg.Pecinicillin
Broad
spectrum
• Act on only particular genera
or species and effective
• Eg. Vancomycin
Narrow
spectrum

5. History
• 1929, Alexander Flemming
• Penicillin G
• Penicillium chrysogenum
•  lactum antibiotic
1939, Howard Flory
Large scale production
Effective for treatment of Staphylococcus
and pneumococcus infection
1945, General use
Discovery of several new
antibiotics

9.  Lactum antibiotics
• Peptidoglycon
•  lactum ring
• Penicillin, Cephalosporin, cephalomycin
• Cell wall synthesis
• Transpeptidation Transpeptidase Penicillin binding
proteins
Antibiotic- PBP complex

10. Protein synthesis
• Initiation and elongation
• Streptomycin
• Puromycin, Chlorumphenical,
Cydoheximide, Tetracyclin
DRAWBACK
Prokaryotic ribosome specific
Effective for mitochondrial ribosomes
E P A
puromycin

11. AMINOGLYCOSIDIC ANTIBIOTICS
Aminosugars bonded by glycosidic linkage
Inhibit protein synthesis at 30s subunit
Gram negative bacteria
Kanamycin, Neomycin, Amikacin
MACROLIDE ANTIBIOTICS
Macrolactone ring
Inhibit protein syntheisis in 50s subunit

13. Transcription
• Rifampin, Streptovarian -  subunit of RNA polymerase
• Actinomycin – Combing with DNA and inhibit RNA elongation

16. Resistance Mechanism
• R plasmid
Mutational alteration – fluoroquinolones
Enzyme inactivation – penicillinase,  lactamase, APH, AAC
Modification of target

17. Multidrug resistance pathogens
• VRE – vancomycin
• MRSA – methicillin, aminoglycosides, tetracyclin, chloramphenicol
• ESBLS - penicillin
Gram negative bacteria are resistant to essentially all of the
available agents