ANTIBIOTICS

B C MUTHU BHARATHII M.Sc., biotechnology

What is antibiotic?

•A microorganism to another microorganism•Chemical substances•Bacteria and fungiExamples

vancomycin puromycinpenicillin chlorumphenicol

Classification

Natural antibioticsfrom microorganismsno structural or chemical modificationEg. Penicillin G ( against gram positive bacteria)

Semisynthetic antibioticChemical or structural modificationEg. Modified semisynthetic pecinillin( against gram

negative too)

• Act on both gram positive and gram negative

• Eg.Pecinicillin

Broad spectru

m• Act on only particular

genera or species and effective

• Eg. Vancomycin

Narrow spectru

m

History

• 1929, Alexander Flemming• Penicillin G• Penicillium chrysogenum• lactum antibiotic

1939, Howard Flory Large scale productionEffective for treatment of Staphylococcus and pneumococcus infection

1945, General useDiscovery of several new antibiotics

Lactum antibiotics

• Peptidoglycon• lactum ring• Penicillin, Cephalosporin, cephalomycin • Cell wall synthesis• Transpeptidation Transpeptidase Penicillin

binding proteins Antibiotic- PBP complex

Protein synthesis

• Initiation and elongation• Streptomycin• Puromycin, Chlorumphenical, Cydoheximide, TetracyclinDRAWBACK

Prokaryotic ribosome specificEffective for mitochondrial ribosomes

E P A

puromycin

AMINOGLYCOSIDIC ANTIBIOTICSAminosugars bonded by glycosidic linkageInhibit protein synthesis at 30s subunitGram negative bacteriaKanamycin, Neomycin, Amikacin

MACROLIDE ANTIBIOTICSMacrolactone ring

Inhibit protein syntheisis in 50s subunit

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

Resistance Mechanism

• R plasmidMutational alteration – fluoroquinolonesEnzyme inactivation – penicillinase, lactamase, APH, AACModification of target

Multidrug resistance pathogens

• VRE – vancomycin • MRSA – methicillin, aminoglycosides, tetracyclin,

chloramphenicol• ESBLS - penicillin

Gram negative bacteria are resistant to essentially all of the available agents