antibiotics.pptx

1. CHEMOTHERAPY
AND
ANTIBIOTICS
Dr.Manoj Mahadev
ICO/Microbiologist

2. INTRODUCTION
Antibiotics (Greek anti, “against”; bios, “life”) are chemical
compounds used to kill or inhibit the growth of infectious
organisms. Originally the term antibiotic referred only to organic
compounds, produced by bacteria or molds, that are toxic to other
microorganisms.
They are more toxic to an invading organism than they are to an
animal or human host.
First antibiotic was penicillin, discovered accidentally from a mold
culture.
Antibiotics only treat bacterial infections. Antibiotics are useless
against viral infections (for example, the common cold) and fungal
infections (such as ringworm).

3. ANTIBIOTICS
CLASSIFICATION ON THE BASIS OF NAME

4. ANTIBIOTICS
CLASSIFICATION BY THEIR MECHANISM OF ACTION
1.Inhibit bacterial cell wall synthesis: Penicillin
Cephalosporin
Cycloserin
Vancomycin
2. Cause leakage from cell membrane: Polypeptides
Polymixin
Colistin
Bacitracin
Polyenes
AmphotericinB
Nystatin
Hamycin
3. Cause misreading of m-RNA
code
and affect permeability :
Aminoglycosides
Streptomycin
Gentamycin
Neomycin

5. ANTIBIOTICS
4. Inhibit protein synthesis: Tetracyclin
Chloramphenicol
Erythromycin
Clindamycin
Linezolid
5. Inhibit DNA gyrase: Fluoroquinolones
Ciprofloxacin
Norfloxacin
Ofloxacin
6. Interfere with metabolism : Sulfonamides
Ethambutol
7. Interfere with DNA function : Rifampin
8. Interfere with DNA synthesis : Metronidazole

6. ANTIBIOTICS
DESCRIPTIONS:
1
. Β-Lactam antibiotics:
Penicillin
Cephalosporin
Carbapenems : Imipenem, Meropenem, Faropenem
A. PENICILLIN: Penicillin was the first antibiotic to be used clinically in 1941.
It was originally obtained from fungus Penicillium notatum.
Mechanism of action:
Binds to Penicillin-binding protein
Inhibit the Transpeptidase activity in
cell wall formation
Transpeptidation i.e cross linking
between peptides not occur.
Peptidoglycan cell wall not form.
bacterial cell wall synthesisinhibited.
Uses:
streptococcal infection
pneumococcal infection
meningococcal infection
gonorrhea, syphilis
Diphtheria
Tetanus
gas gangrene

7. ANTIBIOTICS SURYA
B. CEPHALOSPORIN : These are group of semisynthetic
antibiotics derived from Cephalosporin-C,obtained from
a fungus Cephalosporium. They are chemically related to
penicillin. Its nucleus consist of β-lactum ring.
• Their MOA(Mechanism of action) is same as penicillin, i.e
inhibition of bacterial cell wall synthesis. All
cephalosporins are bactericidal.
Cephalosporin
Ist gen:
Cephalexin,
cephalothin,
Cephadroxil
IInd gen:
Cefaclor,
Cefuroxime,
Cefoxitin
IIIrd gen:
Cefixime,
Cefpodoxime,
Ceftriaxone,
Cefdinir
IVth gen:
Cefepime,
Cefpirome

8. ANTIBIOTICS SURYA
• Ist generation:
Broad spectrum than Penicillin.
Active against both gram+ve and gram-ve organisms.
• IInd generation:
Active against many gram-ve organisms which are resistant to
Ist generation.
• IIIrd generation:
Gram+ve : less active than Ist generation
Gram -ve : more active.
• IVth generation:
Gram +ve : more active than IIIrd generation.
Gram –ve : excellent active against gram –ve.

9. ANTIBIOTICS
2. AMINOGLYCOSIDES:
Aminoglycosides are the drugs effective against gram-ve bacteria. All
aminoglycosides are produced by soil actinomycetes. Aminoglycosides are
bactericidal.
Mechanism of action : Cause misreading of m-RNA code and
affect permeability. Other antibiotics which inhibit protein
synthesis are only static.
Aminoglycosides
Diffuse across outer coat of gram-ve bacteria (e-
transport, O2 dependent, only aerobes)
Bind to 30s (streptomycin), 50s (others), 30s-50s
interface. Protein synthesis initiation stopped.
Cause distortion of mRNA codon recognition.
Misreading of mRNA code. Wrong amino acid enters the
peptide chain.
Abnormality occur. Bacteria become more permeable
and leak out ions, amino acids and protein.

10. ANTIBIOTICS
• Uses : Tuberculosis
Subacute bacterial endocarditis
pseudomonas, proteus or klebsiella infection
Meningitis caused by gram-ve bacteria
Neomycin is used topically for infected wounds, ulcers, burn,
external ear infection, conjuctivitis, post operative infections.
Systemic
•Streptomycin
•Gentamycin
•Kanamycin
•Tobramycin
•Amikacin
Topical
•Neomycin
•Framycetin

11. ANTIBIOTICS
3 .MACROLIDES: Macrolides are the antibiotics having a
macrocyclic lactone ring with attached sugar. They are bacteriostatic.
Erythromycin is the first member discovered.
• Mechanism of action : Macrolides bind to 50s ribosome and
interfere with translocation.
When peptide bond forms between amino acid & peptide
chain at acceptor site (A).
The elongated chain is translocated back to peptidyl site (P).
Thus site (A) becomes available for next amino acyl-t-RNA
attachment. This is called translocation.
Erythromycin binds to 50s ribosome and inhibit this
translocation.
Thus protein synthesis inhibited.

12. ANTIBIOTICS
• Macrolides covers mostly gram+ve and a few gram-ve baterias.
Erythromycin is highly active against:
Str. Pyogenes
Str. Pneumaniae
N. gonorrhoeae
C. diphtheriae
Uses : severe campylobacter enteritis
pertusis
chlamydial infection
pneumonia, sinusitis, bronchitis
Brands : ALTHROCIN – ALEMBIC (erythromycin)
EROATE – LUPIN (erythromycin)
AZEE – CIPLA (azithromycin)
AZRO – PIRAMAL (azithromycin)
CELEX – GSK (clarithromycin)

13. ANTIBIOTICS
4. TETRACYCLINES: These are the antibiotics having a nucleus of
four cyclic rings. They are obtained from soil actinomycetes. They
are primarily bacteriostatic.
Mechanism of action :
• Tetracycline
• Oxytetracycline
• Doxycycline
• Domeclocycline
• Minocycline
• Uses:
Cocci : N. gonorrhoeae & N. meningitides
Bacilli : Gram+ve : Corynebateria, Propionibacterium acnes, B.anthracis
Gram-ve : V. cholera, Yersinia pestis , Helicobacter pylori
Binds to 30s ribosomes
Attachment of aminoacyl-t-RNA to the
mRNA ribosome complex is interfered
Peptide chain fails to grow
protein synthesis inhibited
Bacteriostatic action.

14. ANTIBIOTICS
5. CHLORAMPHENICOL: Chloramphenicol was initially
obtained from Streptomyces venezuelae.
Antibacterial spectrum:
It is primarily bacteriostatic. Active against gram+ve & gram-ve
organisms same as tetracyclin.
Like tetracyclin it is inactive against Mycobacterium, Pseudomonas,
many proteus, viruses and fungi.
Mechanism of action:
Chloramphenicol
binds to 50s ribosome
inhibit the transfer of elongated peptide chain to the
newly attached aminoacyl -tRNA at ribosome mRNA
complex.
Protein synthesis inhibited.

15. ANTIBIOTICS
• Uses:
Bacterial meningitis
Brain abscess
Gas gangrene : death & decay of wound tissues infected by soil
bacterium Clostridium. Toxins produced cause tissue decay and
generate gas.
Whipple’s disease : less absorption of digested food in intestine,
occur in males.
Severe gastroenteritis
Plague
• Brands: CHLOREXIN CAP- CIPLA
DEXOREN- INDOCO PERAXIN
• CHLOROMYCETIN CAP- PFIZER

16. ANTIBIOTICS
6. GLYCOPEPTIDES :
It is active against MRSA. It is bactericidal to gram+ve cocci, Neisseria,
clostridia and diphtheroids.
• Mechanism of action:
It inhibits the bacterial cell wall synthesis.
vancomycin
binds to terminal dipeptide 'D-ala-Dala'
sequence of peptidoglycan unit
prevents the assembly and cross linking of
these units
cell wall not form
• Uses: Staphylococcal enterocolitis Septicemia, Osteomyelitis.
• Brands : VANCOGEN – ALKEM
VANLID – CIPLA
VANCORIN – EMCURE
D-alanyl-D-alanine

17. ANTIBIOTICS
7.OXAZOLIDINONE
Linezolid : active against only gram+ve bacterias. It is primarily
bacteriostatic.
• Mechanism of action:
It inhibits bacterial protein synthesis in an early step.
Linezolid
binds to 23s fraction of 50s ribosome
interfere with the formation of N-
formylmethionine-tRNA-70s complex
thus tRNA binding site distorts
Protein synthesis not occur

18. SURYA
ANTIBIOTICS
• Uses : uncomplicated skin and skin structure infection.
Community acquired pneumonia, Nocosomial pneumonia.
• Brands: ALZOLID – ALEMBIC
LIZOLID – GLENMARK
LINOSPAN – CIPLA
8. LINCOSAMIDE:
Clindamycin : it is similar in MOA to erythromycin (inhibit protein
synthesis by binding to 50s ribosome).
• Uses :
Acne, Bacterial vaginosis.
• Brands :
ACNESOL – SYSTOPIC
CLINDAC A – GALDERMA
CTOP – INTAS
Red, tender bumps with white pus at their tips.

19. ANTIBIOTICS
9. FLOROQUINOLONES:
They are quinolone antimicrobials.
• Norfloxacin
• Ciprofloxacin
• Ofloxacin
• Levofloxacin
• Moxifloxacin
Mechanism of action:
• FQs act by inhibiting the enzyme bacterial DNA gyrase.
• DNA gyrase consist of A and B subunits.
• A subunit cause nicking of strand, while B subunit introduce –ve
supercoil into the strand, and then A subunit reseals the strand. This
is necessary to prevent the excessive positive supercoiling of DNA
strands, hence DNA replication occur.
• FQs bind to A subunit and interfere with the strand cutting and
resealing function.

20. ANTIBIOTICS SURYA
Ofloxacin uses:
Brands:
ALPROXEN- ALKEM
EUFOX - LUPIN
OFLOMAC- MACLEODS
OFLOX -CIPLA
• Leprosy
• Uncomplicated gonorrhoea
• UTI
• Chronic bronchitis
• Traveller’s diarrhea
• LRTI
• Bacterial conjunctivitis
• Bacterial corneal ulcer

21. ANTIBIOTICS
Polymyxin-B & COLISTIN
• Active against only gram-ve bacteria. They are bactericidal. They
cause distortion in bacterial cell membrane and cause pseudopore
formation, so that ions, amino acids leak out and bacteria dies.
• Uses: ocular and skin infections.
• Brands: NEOSPORIN – GSK
CADIPRIM – CADILA
ORIPRIM – ZYDUS CADILA
BACITRACIN
Mostly active against gram+ve bacterias. Acts by inhibiting cell wall
synthesis. Highly toxic so not given parenterally.

22. ANTIBIOTICS
Resistance to antibiotics:
Types of Resistance:
Resistance of bacteria to the effects of antibiotics has become a major
problem in the treatment of disease. Bacteria that are not killed or
stopped by antibacterial drugs may change in form so that they resist
attack against their cell walls or even produce enzymes that kill the
antibiotics.
Resistance: When any
antibiotic does not show
affect against specific
microbes then it means drug
resistance is developed.
Natural: some antibiotics are
naturally resistant to specific
microbes.
Eg- Penicillin is resistant to
gram-ve bacteria,
Tetracyclin is resistant to M.
tuberculosis.
Acquired: microbes become
resistant due to use of
antibiotics for a long period of
time.
Eg- Sulfonamides are resistant
to Gonococci