Antibacterial agents

All about Antibiotics and how their action!!

1. ANTIBACTERIAL AGENTS I AM ANTIBACTERIA.. I AM BACTERIA …PLZ SPARE ME…. BY: MINHAZ AHMED Intgrated M.Sc 4 th sem BBI11014

2. What are antibacterial agents ? An  antibacterial  is an agent that inhibits bacterial growth or kills bacteria . often used  synonymously with the term  antibiotic(s ). The term  antibiotic  was first used in 1942 by Selman Waksman.

3. WHY ANTIBACTERIALS? Bacterial Leaf Blight  of soybean is caused by the bacterium  Psuedomonas syringae Bacterial Canker Bacterial conjuctivities : pink eye Skin spots by bacterial activities

4. HOW ARE THEY CLASSIFIED? on the basis of chemical/biosynthetic  origin into Natural (ex- penicillin ) semisynthetic synthetic(ex- Sulfanilamide) On biological activity; according to their biological effect on microorganisms :  bactericidal agents kill bacteria, and   bacteriostatic agents slow down or stall bacterial growth.

5. The bacterial cell The success of antibacterial agents owes much to the fact that they can act selectively against bacterial cells rather than animal cells. This is largely due to the fact that bacterial cells and animal cells differ both in their structure and in the biosynthetic pathways which proceed inside them.

6. WHERE THEY WORK ? Rifamycins Cell wall Penicillins Cephalosporins cycloserine polymyxins sulfonamides Chloramphenicol Streptomycin tetracyclines Ribosomes capsule cytoplasm

7. MECHANISM OF ACTIONS Inhibition of cell wall synthesis Inhibition of bacterial protein synthesis Inhibition of Nucleic Acid Synthesis Inhibition of Folic Acid Synthesis Penicillins Cephalosphorins Imipenem Meropenem Aztreonam vancomycin Aminoglycosides Chloramphenicol Macrolides Tetracycline Streptogrmins linezolid Fluoroquinolones Rifampin Sulfonamides Trimethoprim Pyrimethamine

8. Inhibition of cell wall synthesis: Penicillins, cephalosphorins , imipenem , meropenem , aztreonam , vancomycin bacteriocidal Must have beta- lactum ring in them which binds and blocks transpeptidases   known as penicillin-binding proteins(PBP) which causes the final cross links between the pentapeptides of peptidoglycan layer. Penicillin cephalosporin Mechanism of resistance: Penicillinases : break the beta lactam ring structure ( staphylococci) Structural changes in PBP’s (MRSA), S. pneumococci Change in porin structure: concerns the gram negative organism

9. Inhibition of bacterial protein synthesis Aminoglycosides,Chloramphenicol,Macrolides,Tetracycline,Streptogrmins, Linezolid . Bactericidal and bacteriostatic .  The primary steps in the process that are attacked are the formation of the 30S initiation complex (made up of mRNA, the 30S ribosomal subunit and formyl - methionyl -transfer RNA),ex Streptomycin (A-glycosides) the formation of the 70S ribosome by the 30S initiation complex and the 50S ribosome,ex Kanamycin  and  tobramycin and the elongation process of assembling amino acids into a polypeptide.ex   Lincomycin , chloramphenicol . RIBOSOME

10. Erythromycin: Binds to 50S-rRNA & prevents movement along mrna

11. Streptomycin Mechanisms of resistance: a mutation of ribosomal binding site enzymatic modification of antibiotic an active efflux of antibiotic out of cell

12. Inhibition of Nucleic Acid Synthesis Fluoroquinolones ( levofloxacin , norfloxacin ) , Rifampin Bacteriocidal Can inhibit DNA gyrase or RNA polymerase Mechanism of resistance: an alteration of alpha subunit of DNA gyrase (chromosomal) beta subunit of RNA polymerase (chromosomal) is altered

13. Quinolones are a key group of antibiotics that interfere with DNA synthesis by inhibiting topoisomerase , most frequently topoisomerase Iv and topoisomer ii (DNA gyrase ) , an enzyme involved in DNA replication. DNA gyrase relaxes supercoiled DNA molecules and initiates transient breakages and rejoins phosphodiester bonds in superhelical turns of closed-circular DNA. This allows the DNA strand to be replicated by DNA or RNA polymerases.

14. Rifampicin  blocks initiation of RNA synthesis by specifically inhibiting bacterial RNA polymerase. It does not interact with mammalian RNA polymerases, making it specific for Gram-positive bacteria and some Gram-negative bacteria. Mechanism of resistance: an alteration of alpha subunit of DNA gyrase (chromosomal) beta subunit of RNA polymerase (chromosomal) is altered

15. Inhibition of Folic Acid Synthesis Sulfonamides , Trimethoprim , Pyrimethamine Bacteriostatic Binds and blocks enzymes mainly pteridine synthesase , dihydrofolate reductase responsible for folic acid synthesis. What are Folic Acid? Folic acid enzymes are nessary for the synthesis of amino acids, hence necessary for bacterial protein synthesis. Folic acid

16. Sulfonamide functional group trimethoprim Pyrimethamine Pyrimethamine Mechanism of resistance: Mutations in the gene for dihydrofolate reductase decreasing binding affinity .

17. Some Side affects of antibacterial agents ANTIBACTERIAL AGENTS SIDE EFFECTS Aminoglycosides renal (kidney) toxicity, ototoxicity (hearing loss), dizziness, nausea/vomiting, nystagmus Sulfonamides nausea/vomiting, diarrhea, anorexia, abdominal pain, rash, photosensitivity, headache, dizziness Tetracyclines nausea/vomiting, diarrhea, anorexia, abdominal pain, tooth discoloration in children < 8 years, liver toxicity Quinolones nausea/vomiting, diarrhea, abdominal pain, headache, lethargy, insomnia, photosensitivity (can be severe)

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