Antibiotics

This presentation contains brief introduction about antibiotics and its classification with mode of actions.

1. A PRESENTATION BY SURYA PRAJAPAT
ANTIBIOTICS SURYA













ANTIBIOTICS

2. ANTIBIOTICS SURYA
INDEX
1.INTRODUCTION
2.CLASSIFICATION
3.DESCRIPTIONS & MODE OF ACTION
• Β-LACTAM
• AMINOGLYCOSIDES
• MACROLIDES
• TETRACYCLIN
• CHLORAMPHENICOL
• GLYCOPEPTIDES
• OXAZOLIDINONE
• LINCOSAMIDES
• FLUOROQUINOLONES
• OTHERS
4.RISISTANCE TO ANTIBIOTICS

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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).

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•CLASSIFICATION:

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•classification by their mechanism of action:
1.Inhibit bacterial cell wall synthesis: Penicillin
Cephalosporin
Cycloserin
Vancomycin

2. Cause leakage from cell membrane: Polypeptides polyenes
Polymixin AmphotericinB
Colistin Nystatin
Bacitracin Hamycin

3. Cause misreading of m-RNA code
and affect permeability : Aminoglycosides
Streptomycin
Gentamycin
Neomycin

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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

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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 synthesis inhibited.

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•Eg: Penicillin G Uses:
Penicillin V streptococcal infection
Naficillin pneumococcal infection
Methicillin meningococcal infection
Ampicillin gonorrhea, syphilis
Amoxycillin Diphtheria
Tetanus
gas gangrene

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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 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

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•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.

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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, O
2 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.

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•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

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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.

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•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)

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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.

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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.

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•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 – PIRAMAL
CHLOROMYCETIN CAP- PFIZER

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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.









• Uses: Staphylococcal enterocolitis Septicemia, Osteomyelitis.
• Brands : VANCOGEN – ALKEM
VANLID – CIPLA
VANCORIN – EMCURE

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

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7.OXAZOLIDINONE :
Linezolid : active against only gram+ve bacterias. It is primarily
bacteriostatic.
•Mechanism of action:
It inhibits bacterial protein synthesis ta an early step and different
site than other.

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

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•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

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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.

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

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10.OTHERS:
A.Mupirocin
B.Polypeptides
i. Polymyxin-B
ii. Colistin
iii. Bacitracin

•MUPIROCIN
•It is a novel antibiotic produced through fermentation of
Pseudomonas fluorescens. It inhibits isoleucyl transfer-RNA
synthetase and arrestbacterial protein synthesis.
•Uses:
Primary skin infection- impetigo, folliculitis, furunculosis, ecthyma.
Secondary skin infection- eczema, abrasion, lesions, insect bites,
wounds, cuts.
•Brands: BACTROBAN – GSK
MPOWER- ZYDUS
SUPIROCIN - GLENMARK

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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, autic 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.

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Resistance to antibiotics:
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.
Types of Resistance:



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

26. THANK YOU
A PRESENTATION BY SURYA PRAJAPAT