Antibiotics By

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AntibioticsBy

• Dr. Humodi A. Saeed
• Associate Prof. of Medical Microbiology
• College of Medical Lab. Science
• Sudan University of Science and Technology
• E mail address Biotechsust_at_hotmail.com

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Definition of Antibiotic

• A substance of biological, semisyntheticor
  synthetic origin of low molecular weight
• (on-protein) produced by a fungus or
  bacterium as secondary metabolites that inhibits
  or stop growth of other microorganisms in vitro
  and in vivo selectively, when it used in low
  concentration

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Characteristics of Antibiotics

• It must be able to reach the part of the human
  body where the infection is occurring.

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Characteristics of Antibiotics

• It should not cause the development of resistant
  forms of parasites.

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Characteristics of Antibiotics

• It should not produce undesirable side effects in
  the host such as allergic reaction, nerve damage
  or irritation of the kidneys and gastrointestinal
  tract.

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Characteristics of Antibiotics

• It should be given orally without inactivation by
  stomach acid, or by injection (parenterally)
  without binding to the blood proteins.

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Characteristics of Antibiotics

• Finally, it should have a high level of
  solubility in the body fluids and be possible to
  achieve concentrations in the tissue or blood,
  which are sufficiently high to inhibit or kill
  the infectious agent.

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Major groups of Antibiotics

• 1. Beta-lactam antibiotics
• 1. Penicillins
• 2. Cephalosporins
• 3. Carbapenems
• 4. Monobactams

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1. Beta-lactam antibiotics Toxicity Problem

• The main toxicity problem with these antibiotics
  is an allergic reaction that occurs because of
  formation of beta-lactam/serum protein conjugate
  that elicits an inflammatory immune response.

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1. Beta-lactam antibiotics Mode of Action

• The beta-lactam antibiotics inhibit the last step
  in peptidoglycan synthesis

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1. Beta-lactam antibiotics Spectrum

• Some are effective against both Gram-positive and
  Gram-negative bacteria whereas others are more
  effective against Gram-positive than
  Gram-negative bacteria or vice versa.

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1. Beta-lactam antibiotics Example 1. ( Natural
penicillins and
cephalosporins )

• Penicillin G, Cephalothin
• ?Biological source
• Penicillium notatum
• Cephalosporium species
• ?Spectrum (effective against)
• Gram-positive bacteria
• ?Mode of action
• Inhibits steps in cell wall (peptidoglycan)
  synthesis.

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1. Beta-lactam antibiotics Example 2. (
Semisynthetic penicillin)

• Ampicillin, Amoxycillin
• ?Spectrum (effective against)
• Gram-positive and Gram-negative bacteria
• ?Mode of action
•  Inhibits steps in cell wall (peptidoglycan)
  synthesis.

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1. Beta-lactam antibiotics Example 3.
(Clavulanic Acid )

• Clavamox is clavulanic acid plus amoxycillin
• ?Biological source
• Streptomyces clavuligerus
• ?Spectrum (effective against)
• Gram-positive and Gram-negative bacteria
• ?Mode of action
• Suicide inhibitor of beta-lactamases

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Example 4. (Monobactams )

• Aztreonam
• ?Biological source
• Chromobacter violaceum
• ?Spectrum (effective against)
• Gram-positive and Gram-negative bacteria
• ?Mode of action
• Inhibits steps in cell wall (peptidoglycan)
  synthesis and murein assembly

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1. Beta-lactam antibiotics Example 5. (
Carboxypenems )

• Imipenem
• ?Biological source
• Streptomyces cattleya
• ?Spectrum (effective against)
• Gram-positive and Gram-negative bacteria
• ?Mode of action
• Inhibits steps in cell wall (peptidoglycan)
  synthesis.

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2. Glycopeptides

• Another group of peptidoglycan synthesis
  inhibitors is the glycopeptides, exemplified by
  vancomycin and teichoplanin.

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2. Glycopeptides

• Vancomycin
• ?Biological source
• Streptomyces orientales
• ?Spectrum (effective against)
• ?Gram-positive bacteria, esp. Staphylococcus
  aureus
• ?Mode of action
• Inhibits steps in murein (peptidoglycan)
  biosynthesis

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3. Aminoglycosides

• Members of this group contain sugars and consists
  of streptomycin, dihydrostreptomycin, neomycin,
  framycetin, gentamicin, kanamycin, paromycin,
  tobramycin and amikacin.

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3. Aminoglycosides

• Example 1.
• Gentamicin
• ?Biological source
• Micromonospora species
• ?Spectrum (effective against)
• Gram-positive and Gram-negative bacteria esp.
  Pseudomonas
• ?Mode of action
• Inhibit translation (protein synthesis)

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3. Aminoglycosides

• Example 2
• Streptomycin
• ?Biological source
• Streptomyces griseus
• ?Spectrum (effective against)
• Gram-positive and Gram-negative bacteria
• ?Mode of action
• Inhibit translation (protein synthesis)

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4. Tetracyclines

• Tetracyclines consist of eight members, and may
  be considered as a group of antibiotics, obtained
  as byproducts from the metabolism of various
  species of Streptomyces .

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4. Tetracyclines

• Example 1.( Natural )
• Tetracycline
• ?Biological source
• Streptomyces species
• ?Spectrum (effective against)
• Gram-positive and Gram-negative bacteria,
  Rickettsias
• ?Mode of action
• Inhibit translation (protein synthesis)

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4. Tetracyclines

• Example 2. (Semisynthetic tetracycline)
• Doxycycline
• ?Spectrum (effective against)
• Gram-positive and Gram-negative bacteria,
  Rickettsias Ehrlichia, Borellia
• ?Mode of action
• Inhibit translation (protein synthesis)

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5. Macrolides

• Macrolides are an ill-defined group representing
  those antibiotics that have large ring structures
  containing oxygen.

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5. Macrolides

• Example
• Erythromycin
• ?Biological source
• Streptomyces erythreus
• ?Spectrum (effective against)
• Gram-positive bacteria, Gram-negative bacteria
  not enterics, Neisseria,Legionella, Mycoplasma
• ?Mode of action
• Inhibits translation (protein synthesis)

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6. Lincosamides

• Lincosamides are a family of antibiotics that
  bind to bacterial 50S ribosomal subunit. They
  differ considerably from macrolides in structure.

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6. Lincosamides

• Example
• Clindamycin
• ?Biological source
• Streptomyces lincolnensis
• ?Spectrum (effective against)
• Gram-positive and Gram-negative bacteria esp.
  anaerobic Bacteroides
• ?Mode of action
• Inhibits translation (protein synthesis)

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7. Quinolones

• Quinolones are a family of antibiotics that
  interferes with DNA replication. Quinolones are
  bactericidal antibiotics.
• Nalidixic acid
• Ciprofloxacin
• Norfloxacin
• Ofloxacin

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8. Rifampin

• Rifampin (or Rifampicin) is an antibiotic that
  inhibits bacterial RNA polymerase by binding to
  its ß-subunit. Rifampin is a bactericidal
  antibiotic.

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9. Polypeptides

• Example 1
• Polymyxin
• ?Biological source
• Bacillus polymyxa
• ?Spectrum (effective against)
• Gram-negative bacteria
• ?Mode of action
• Damages cytoplasmic membranes

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9. Polypeptides

• Example 2
• Bacitracin
• ?Biological source
• Bacillus subtilis
• ?Spectrum (effective against)
• Gram-positive bacteria
• ?Mode of action
• Inhibits steps in murein (peptidoglycan)
  biosynthesis.

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10. Polyenes

• Example 1.
• Amphotericin
• ?Biological source
• Streptomyces nodosus
• ?Spectrum (effective against)
• Fungi
• ?Mode of action
• Inactivate membranes containing sterols

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10. Polyenes

• Example 2.
• Nystatin
• ?Biological source
• Streptomyces noursei
• ?Spectrum (effective against)
• Fungi (Candida)
• ?Mode of action
•  Inactivate membranes containing sterols

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. Rifamycins11

• Examples
• Rifampicin
• ?Biological source
• Streptomyces mediterranei
• ?Spectrum (effective against)
• Gram-positive and Gram-negative bacteria,
  Mycobacterium tuberculosis
• ?Mode of action
• Inhibits transcription (eubacterial RNA
  polymerase)

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12. Phenols

• Example
• Chloramphenicol
• ?Biological source
• Streptomyces venezuelae
• ?Spectrum (effective against)
• Gram-positive and Gram-negative bacteria
• ?Mode of action
• Inhibits translation (protein synthesis)

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Resistance to Antibiotics
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Resistance to Antibiotics
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Resistance to Antibiotics
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Resistance to Antibiotics
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Resistance to Antibiotics
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Antibiotics Susceptibility Tests