Download - Antibacterial agents
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)
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