This presentation offers a concise overview of antibiotics, facilitating rapid review.

1. Prepared by
Dhanushya.G
II Semester
Department of Pharmacology
PSG College of Pharmacy
SUMMARIZATION OF
ANTIBIOTICS
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2. Contents
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1.Antibiotics-introduction
2.Bacteria
2.1.Bacterial cell wall
structure
3.Antibacterial agents
3.1.Targets
3.2.Mechanism of action
3.3.Features of antibiotics
3.4.Development of
resistance
3.5.Antimicrobial action
4.Antibiotics-classification
4.1.Beta lactam antibiotics
4.1.1.Penicillin
4.1.2.Cephalosporins
4.1.3.Carbapenems
4.1.4.Monobactams
4.2.Aminoglycosides
4.3.Quinolones &
fluoroquinolones
4.4.Macrolide antibiotics
4.5.Others
4.5.1.Tetracyclines &
chloramphenicol
4.5.2.Lincosamide
antibiotics
4.5.3.Glycopeptide
antibiotics
4.5.4.Polypeptide antibiotics

3. 1.Antibiotics-introduction
 Antibiotics are those substances which selectively
suppress the growth of / kill other microorganisms
at very low concentration.
 Antibiotics are primarily applied to antibacterial
agents.
 Characteristics:
Selectivity: Attack the bacterial cell without
affecting the host.
Action: Bactericidal
Resistance: Not likely to induce resistance.
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4. 2.Bacteria
 Bacteria are microbes which comprises of some
harmful strains. These harmful strains cause
infection which lead to the discovery of
antibiotics.
 Bacteria can affect any area of the body.
CLASSIFICATION
Gram positive
Thick peptidoglycan layer
No outer lipid membrane
Gram negative
Thin peptidoglycan layer
Has an outer lipid membrane
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5. 2.1.Bacterial cell wall structure
 The type of bacteria is found by staining the cell.
 Gram positive retains the blue colour whereas
gram negative doesnot retain.
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6. 3.Antibacterial agents
3.1.Targets
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7. 3.2.Mechanism of action
• Beta-lactam antibiotics
• Bacitracin
Inhibit cell wall synthesis
• Tetracyclines
• Chloramphenicol
Inhibit protein synthesis
• Rifampin
Interfere with DNA function
• Polymixin
• Amphotericin B
Cause leakage from cell
membrane
• Fluoroquinolones
Inhibit DNA gyrase
• Sulfonamides
Interfere with intermediary
metabolism
• Aminoglycosides
Cause misreading of m-RNA
& affect permeability
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8. 3.3.Features of antibiotics
 Problems associated:
 Toxicity
 Local irritancy
 Systemic toxicity
 Hypersensitivity reactions
 Drug resistance
 Natural resistance
 Acquired resistance
 Superinfection
 Nutritional deficiencies
 Masking of an infection
 Antimicrobial action: bacteriostatic vs
bactericide
 Activity spectrum: broad-spectrum vs narrow-
spectrum
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9. 3.4.Development of resistance
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10. 3.5.Antimicrobial action
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11. 4.Antibiotics-classification
4.1.B-lactam antibiotics
 These are antibiotics with a b-lactam ring.
Classification :
 Penicillins
 Cephalosporins
 Carbapenems
 Monobactams
MOA:
 Inhibit synthesis of peptidoglycan layer of bacterial
cell wall.
 The irreversible inhibition of the antibiotic binding
proteins prevents the final crosslinking of the
peptidoglycan layer- disrupt cell wall synthesis.
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13. 4.1.1.Penicillins
 First antibiotic with least toxicity.
CLASSIFICATION:
Natural: Penicillin G
Semisynthetic:
 Acid resistant: Penicillin V
 Penicillinase resistant: Methicillin, Cloxacillin,
Dicloxacillin
 Extended spectrum penicillins:
 Amino – penicillins: Ampicillin, Bacampicillin, Amoxicillin
 Carboxy – penicillins: Carbenicillin, Ticarcillin
 Ureido – penicillins: Piperacillin, Mezlocillin
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14. RESISTANCE:
 Resistance to penicillins develops due to b-lactamase,the
enzyme which opens the b-lactam ring & inactivates it.
 To overcome resistance, b-lactamase inhibitors have
been used-
 Clavulanic acid
 Sulbactam
 Tazobactam
USES:
 Skin & soft tissue infection
 Diphtheria,Tetanus
 UTI
 Respiratory tract infection
 Intra abdominal infection
 Syphilis, Gonorrhea
 Streptococcal infection
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15. 4.1.2.Cephalosporins
CLASSIFICATION:
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16. ADVERSE EFFECTS:
 Pain after injection
 Diarrhoea
 Hypersensitivity reaction
 Bleeding
USES:
 Alternative to penicillin
 Respiratory,urinary,soft tissue infections caused by
gram-negative organisms
 Meningitis
 Gonorrhea
 Typhoid fever
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17. 4.1.3.Carbapenems
4.1.4.Monobactams
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DRUGS:
Imepenem
Meropenem
Faropenem
Doripenem
Ertapenem
USES:
Multi drug
resistant(MDR) bacterial
infections.
 Aztreonam:
 Atypical b-lactam
antibiotic as one ring
is missing.
 USES:
 Hospital acquired
infections.

18. 4.2.AMINOGLYCOSIDES
CLASSIFICATION:
 Systemic:
 Streptomycin
 Gentamycin
 Kanamycin
 Tobramycin
 Amikacin
 Netilmicin
 Sisomicin
 Paromomycin
 Topical
 Neomycin
 Framycetin
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 Effective against gram-
negative organisms.
MOA:
Spectrum of activity:
 Aerobic gram –ve
bacteria
 Mycobacteria
 Brucella
Characteristics:
 Highly polar
cation- limited
distribution
 Low activity in low
pH

20. RESISTANCE:
 Cell membrane bound
modifying enzymes -
phosphorylate /adenylate
/acetylate the antibiotic –
thus no binding.
 Mutation decreases the
affinity of ribisomal proteins
that normally bind to
aminoglycoside.
 Decreased efficiency of
aminoglycoside transporting
mechanism.
TOXIC EFFECTS:
 Ototoxicity
Cochchlear damage &
vestibulat damage occurs.
 Nephrotoxicity
Tubular damage occurs.
 Neuromuscular blockade
Reduce Ach release.
USES:
 Gram negative infections
 Complicated UTI
 Complicated skin & soft
tissue infections
 Endocarditis
 Intraabdominal infections
 Pelvic inflammatory disease
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21. 4.3.Quinolones &
Fluoroquinolones
QUINOLONES:
 Synthetic antibiotic with a quinolone structure.
 Not a first-line drug
 Resistance to quinolones is more common.
 DRUG: Nalidixic acid
 MOA: Inhibit DNA gyrase
 Spectrum of activity: gram –ve bacteria
 Adverse effects: GI upset,rashes,head ache,vertigo,visual
disturbances
 Contraindication:Infants
 Uses: UTI
 Characteristics: Highly protein bound
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22. FLUOROQUINOLONES:
 Modified form of
quinolones
 Characteristics:
 Not highly protein
bound
 Wide distribution-
limited CSF penetration
 DRUGS:
 First generation
 Norfloxacin
 Ciprofloxacin
 Ofloxacin
 Pefloxacin
 Second generation
 Levofloxacin
 Moxifloxacin
 Gemifloxacin
 Prulifloxacin
 Lomefloxacin
 Sparfloxacin
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MOA:
1.During DNA
replication, the
seperation of the two
strands lead to
excessive positive
supercoils.
2.In order to prevent
this over winding,
DNA gyrase
introduces negative
supercoils &
topoisomerase IV
relaxes the positive
supercoils.

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 In gram negative bacteria- FQs inhibit bacterial
DNA gyrase
FQs bind to the A subunit of DNA gyrase &
interfere with its strand cutting & resealing
function
 In gram positive bacteria- FQs target
topoisomerase IV & hinders DNA replication.

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RESISTANCE:
 Chromosomal
mutation- DNA
gyrase/
topoisomerase with
reduced affinity to
FQs.
 Increase in efflux of
drugs.

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ADVERSE EFFECTS:
 CNS: dizziness,
confusion,delerium
 CVS: torsades de
pointes
 GI:
nausea,vomiting
USES:
 UTI
 Typhoid
 Respiratory infection
 Gonorrhea &
chancroid
 Meningitis
 Conjunctivitis

27. 4.4.MACROLIDES
 These are antibiotics with a macrocyclic lactone
ring.
DRUGS:
 Erythromycin
 Clarithromycin
 Azithromycin
 Roxithromycin
 Telithromycin
 Spiramycin
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Inhibits protein
synthesis
Inhibit polypeptide
chain elongation
Macrolides bind to 50s
ribosomal subunit
MOA:

29. RESISTANCE:
Due to
1.Target gene mutation 2.Efflux pump
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Spectrum of activity:
 Gram +ve bacteria
 Mycoplasma
 N.gonorrhea
Characteristic:
 Wide distribution-
restricted to brain &
CSF
ADVERSE EFFECTS:
 Gastrointestinal –
pain,nausea,anorexia
 Reversible hearing
impairment
 Hypersensitivity –
rashes,fever

31. 4.5.Others
4.5.1.Tetracyclines &
Chloramphenicol
TETRACYCLINES:
 Antibiotics with four cyclic rings in the nucleus.
 MOA: Bind to 30s riboSome & inhibit tRNA
attachment to A site.
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Spectrum of activity:
Broad spectrum
ADVERSE EFFECTS:
 Irritative- irritative
diarrhoea,esophageal
ulceration,
thrombophlebitis
 Organ toxicity
 Liver damage
 Kidney damage
 Phototoxixity
 Teeth & bones-chelation
 Vestibulat toxicity
 Hypersensitivity
 Superinfection
USES:
 For empirical
theraphy
 Venereal diseases
 Atypical pneumonia
 Plague
 Relapsing fever
 UTI
 CAP
 Amoebiasis

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CHLORAMPHENICOL
MOA:
 Binds to 50s ribosome- interferes with peptide
bond formation

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RESISTANCE:
 Acquisition of R plasmid
encoded for acetyl
transferase which
inactivates
chloramphenicol.
 Decreased permeability
into resistant cells.
 Low affinity of bacterial
ribosome
ADVERSE EFFECTS:
 Bone marrow
depression
 Idiosyncratic reaction
 Myelosuppression
 Hypersensitivity
reaction
 Irritative effects
 Superinfections
 Gray baby syndrome
USES:
 Pyogenic Meningitis
 Anaerobic Infections
 Introcular Infection
 Enteric Fever

35. 4.5.2.Lincosamide antibiotics
DRUGS:
 Clindamycin
 Lincomycin
MOA:
 Inhibition of protein synthesis by binding to 50s
ribosome
Side effects:
 Rashes,urticaria,abdominal pain
 Diarrhea,pseudomembranous enterocolitis
 Liver damage
 Thrombophlebitis
USES: Acne vulgaris,MDR falciparum
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36. 4.5.3.Glycopeptide antibiotics
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DRUGS:
 Vancomycin
 Teicoplanin
MOA:
 Inhibit bacterial cell wall
synthesis
Toxicity:
 Kidney damage
 Skin allergy
 Red man
syndrome(chills,fever,ur
ticaria,flusing) on i.v
injection
USES:
 Pseudomembranous
enterocolitis
 MRSA infection

37. 4.5.4.Polypeptide antibiotics
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 Low molecular weight
cationic compounds
DRUGS:
 Polimyxin B & Colistin –
act against gram –ve
bacteria
MOA:
 Cause membrane
distortion/pseudopore
formation in bacterial cell
membrane
USES:
 Topical – bruns,otitis
externa,corneal ulcer
 Oral – gram –ve bacillary
infections
 Bacitracin –act against
gram +ve bacteria
MOA:
 Inhibit cell wall synthesis
USES:
 Topical- eye
infection,ulcers.

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