Antibiotic classification based on chemical nature and mode

antibiotcs

1. Antibiotic classification based on chemical nature and mode of action II M.Sc MICROBIOLOGY 18PY04

2. ANTIBIOTIC: Antibiotic are substance produced by microorganisms which suppress the growth / destroy the microorganism. The antibiotics are derives from not only a bacteria and fungi.

3. Antibiotic classification based on mode of action: cell wall synthesis inhibition protein synthesis inhibition. Nucleic acid synthesis inhibition. Folate synthesis inhibition. Membrane disruption.

4. Cell wall synthesis inhibition:

5. Examples of bacterial cell wall synthesis inhibition: Penicillin Cephalosporin Vancomycin Carbapenems Beta lactamase.

6. Penicillin: The bacterial cell wall composed of layers of peptidoglycan , which is made up of repeating unit N-acetyl glucosamine (NAG) and N-acetyl muramic acid (NAM) the NAG and NAM molecules are cross linked with the activity of transglycolase and transpeptidase . The result is that the cell wall is not properly cross-linked

7. Pencillin binds to the PBP and inactivate on the cell wall inhibit the transpeptidase prevent peptidoglycan synthesis cell wall deficient forms autolysis cell death

8. Protein synthesis inhibition: Protein are important to all living cells. In protein synthesis takes place in cytoplasm. Proteins are assembled at a ribosome. In bacterial ribosome which contain 70S is composed of two parts a small 30S subunit and 50S subunit. Each subunit contain ribosomal RNA and proteins. Ribosome contains A and P site.

9. Some antibiotic binds to the both site which blocks the translocation and peptide bond formation. Many antibiotics act at different sites on the bacterial ribosomes to inhibit protein synthesis. Inhibition in 30S subunit : for ex, spectinomycin , aminoglycosides , kanamycin , streptomycin and tetracycline all target the 30S subunit of the ribosome.

10. Inhibition in 30S subunit: In 1 st step ribosome binds to the mRNA then charged tRNA must be placed into the P site of the ribosome. Ex, aminoglycosides Aminoglycosides inhibit the protein synthesis by binding with high affinity to the A site on the 16S ribosomal RNA of the 30S ribosome as a result of this interaction the antibiotic promotes mistranslation by inducing codon misreading on delivery of the aminoacyl tRNA

11. Inhibition in 50S subunit: clindamycin , chloramphenicol , erythromycin, clarithromycin , linezolid all are target to the inhibition of 50 S subunit.

12. Inhibition in 50S subunit: ex, Macrolides are protein synthesis inhibitors. Its inhibit ribosomal translation. Macrolides binds To 50S subunit of ribosome inhibit polypeptide chain elongation and protein synthesis inhibition as a result in inhibition of growth and multiplication

13. Nucleic acid synthesis inhibition: inhibition in RNA synthesis: the antibiotiocs bind to RNA dependent RNA polymerase and inhibit the initiation of RNA synthesis. Ex, rifampin and rifamycin inhibition in DNA synthesis: these antibiotics binds to A subunit of DNA gyrase and prevent supercoiling of DNA thereby inhibiting DNA synthesis. Ex, quinolones and fluroquinolones .

14. Folic acid synthesis inhibition:

15. Membrane distribution: The plasma membrane in bacteria is involved with membrane transport, DNA replication, the production of ATP. some antibiotics are blocks this properties such as polymyxin , daptomycin , telavancin

16. Antibiotic classification based on chemical nature:

17. The presence of macrocyclic lactone ring connected with one or several carbohydrate residues such as amino sugars ex., erythromycin, methymycin

18. 2 Sulfonamides are connected with sulphur group and amine group .

19. Aminoglycosides these compounds containing glycoside bonds in their molecule ex, streptomycin, gentamycin.

20. Polypeptide antibiotics  are a chemically diverse class of anti-infective and antitumor  antibiotics  containing non-protein  polypeptide  chains. Examples of this class include actinomycin , bacitracin , colistin , and polymyxin B. Actinomycin -D 

21. bacteriacin polymyxin

22. THANK YOU