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