ANTIBACTERIAL AGENTS

I AM ANTIBACTERIA..

I AM BACTERIA …PLZ SPARE ME….

BY: MINHAZ AHMED Intgrated M.Sc 4th sem BBI11014

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.

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

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.

The bacterial cellThe success of antibacterial agents owes much to the fact that they can act selectivelyagainst bacterial cells rather than animal cells. This is largely due to the fact thatbacterial cells and animal cells differ both in their structure and in the biosyntheticpathways which proceed inside them.

WHERE THEY WORK?

Rifamycins

Cell wall

PenicillinsCephalosporinscycloserine

polymyxinssulfonamides

ChloramphenicolStreptomycintetracyclines

Ribosomes

capsule

cytoplasm

MECHANISM OF ACTIONS

Inhibition of cell wall synthesis

Inhibition of bacterial protein synthesis

Inhibition of Nucleic Acid Synthesis

Inhibition of Folic Acid Synthesis

PenicillinsCephalosphorinsImipenemMeropenemAztreonamvancomycin

AminoglycosidesChloramphenicolMacrolidesTetracyclineStreptogrminslinezolid

FluoroquinolonesRifampin

SulfonamidesTrimethoprimPyrimethamine

Inhibition of cell wall synthesis:Penicillins, cephalosphorins, imipenem, meropenem, aztreonam, vancomycinbacteriocidalMust 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

Inhibition of bacterial protein synthesisAminoglycosides,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

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

Streptomycin

Mechanisms of resistance:

a mutation of ribosomal binding siteenzymatic modification of antibiotican active efflux of antibiotic out of cell

Inhibition of Nucleic Acid Synthesis

Fluoroquinolones(levofloxacin, norfloxacin),RifampinBacteriocidalCan 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

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.

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

Inhibition of Folic Acid Synthesis

Sulfonamides, Trimethoprim, PyrimethamineBacteriostaticBinds 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

Sulfonamide functional group

trimethoprim

PyrimethaminePyrimethamine

Mechanism of resistance:Mutations in the gene for dihydrofolate reductase decreasing binding affinity .

Some Side affects of antibacterial agentsANTIBACTERIAL 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)

THANK YOU