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					            Antibiotics

                   By

Dr. Humodi A. Saeed
Associate Prof. of Medical Microbiology
College of Medical Lab. Science
Sudan University of Science and Technology
E mail address: Biotechsust@hotmail.com
  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
Characteristics of Antibiotics
 It must be able to 
reach the part of the
 human body where
   the infection is
     occurring.
Characteristics of Antibiotics
It should not cause 
the development of
  resistant forms of
      parasites.
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.
Characteristics of Antibiotics
 It should be given 
     orally without
    inactivation by
stomach acid, or by
       injection
     (parenterally)
 without binding to
the blood proteins.
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.
  Major groups of Antibiotics
       1. Beta-lactam
         antibiotics

1. Penicillins
2. Cephalosporins
3. Carbapenems
4. Monobactams
       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.
    1. Beta-lactam antibiotics
          Mode of Action
The beta-lactam 
antibiotics inhibit
 the last step in
 peptidoglycan
    synthesis
     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.
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.
        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.
      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
    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
      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.
     2. Glycopeptides
Another group of peptidoglycan   
   synthesis inhibitors is the
 glycopeptides, exemplified by
 vancomycin and teichoplanin.
           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
        3. Aminoglycosides
Members of this group contain sugars and consists   
 of streptomycin, dihydrostreptomycin, neomycin,
  framycetin, gentamicin, kanamycin, paromycin,
            tobramycin and amikacin.
         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)
          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)
          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 .
            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)
          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)
             5. Macrolides
     Macrolides are an ill-defined group 
representing those antibiotics that have large
     ring structures containing oxygen.
               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)
           6. Lincosamides
Lincosamides are a family of antibiotics that 
bind to bacterial 50S ribosomal subunit. They
   differ considerably from macrolides in
                   structure.
            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)
             7. Quinolones
  Quinolones are a family of antibiotics that 
 interferes with DNA replication. Quinolones
          are bactericidal antibiotics.
Nalidixic acid
Ciprofloxacin
Norfloxacin
Ofloxacin
              8. Rifampin
Rifampin (or Rifampicin) is an antibiotic that 
inhibits bacterial RNA polymerase by binding
  to its ß-subunit. Rifampin is a bactericidal
                   antibiotic.
        9. Polypeptides
 Example  1
 Polymyxin
 Biological source
 Bacillus polymyxa
 Spectrum (effective against)
 Gram-negative bacteria
 Mode of action
 Damages cytoplasmic membranes
             9. Polypeptides
   Example 2
    Bacitracin
   Biological source
   Bacillus subtilis
   Spectrum (effective against)
   Gram-positive bacteria
   Mode of action
   Inhibits steps in murein (peptidoglycan)
    biosynthesis.
               10. Polyenes
   Example 1.
    Amphotericin
   Biological source
   Streptomyces nodosus
   Spectrum (effective against)
   Fungi
   Mode of action
   Inactivate membranes containing sterols
               10. Polyenes
   Example 2.
   Nystatin
   Biological source
   Streptomyces noursei
   Spectrum (effective against)
   Fungi (Candida)
   Mode of action
    Inactivate membranes containing sterols
           11. Rifamycins
 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)
               12. Phenols
   Example
    Chloramphenicol
   Biological source
   Streptomyces venezuelae
   Spectrum (effective against)
   Gram-positive and Gram-negative bacteria
   Mode of action
   Inhibits translation (protein synthesis)
Resistance to Antibiotics
Resistance to Antibiotics
Resistance to Antibiotics
Resistance to Antibiotics
Resistance to Antibiotics
Antibiotics Susceptibility Tests

				
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posted:12/8/2011
language:English
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