History
 Chemotherapy as a science began with
Paul Ehrlich in the first decade of last
century.
 Ehrlich received the Nobel Prize for
Medicine in 1908.
 In 1906 he discovered the structural
formula of atoxyl, a chemical compound
which had been shown to be able to
treat
sleeping
sickness
(trypanosomiasis).
 In 1909 he and his student Sahachiro
Hata
developed
Salvarsan
(arsphenamine), a treatment effective
against syphilis.
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 Gerhard Domagk was a German
pathologist
and
bacteriologist
recognized with the discovery of the
first
commercially
available
antibiotic (marketed under the brand
name Prontosil).
 In 1939, he received the Nobel Prize
in Medicine for this discovery, the
first drug effective against bacterial
infections (streptococcal infections ).
 Prontosil decomposes in the living
body to give a highly active
sulphonamide
and
the
toxic
compound thiaminobenzene.
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 The 'golden age' of antimicrobial
therapy began with the production
of penicillin.
 This
was
discovered
by
Sir Alexander Fleming (1929) who
noticed that the growth of
staphylococci was inhibited round a
mould of
Penicilian
notatum which was growing by
accident on a culture plate.
 From this mould, penicillin was
extracted and mass produced in
1940 by the work of Florey &
Chain.
• He shared the Nobel Prize in Physiology or Medicine in
1945 with Howard Florey and Ernst Chain.
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 Antibiotics
= a natural substance
produced
by
a micro-organism to kill another.
 Anti-infectives / Anti-microbrial = any agent (natural or
synthetic) that kills pathogens (microbes).
Classification of antibiotics l antibacterial

According to their origin (sources)

According to their chemical structure

According to the spectrum of their
biological action

According to their mode of action

According to their origin (sources)
Microorganisms
Bacteria
Synthetic antibiotics
Fungi
Streptomyces spp
Semi synthetic antibiotics
Examples of Microbial Sources of Antibiotics
Streptomyces
• Streptomyces is the largest genus of Actinobacteria.
• Over 500 species of Streptomyces bacteria have been
described.

According to their chemical structure
a. Beta-lactam antibiotics
b. Aminoglycosides
c. Aminocyclitols
d. Tetracyclines
e. Polyenes
f. Macrolides
a. Beta-lactam antibiotics
 β-Lactam antibiotics are a broad class of antibiotics,
consisting of all antibiotic agents that contains
a β-Lactam nucleus in its molecular structure.
 It includes penicillins, cephalosporins, and cephmycins.
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b. Aminoglycosides
 An aminoglycoside is a molecule or a portion of
a molecule composed of amino-modified sugars.
 They are glycosidic derivatives of streptamine.
 Both streptomycin and dihydrostreptomycin contain
streptidin and aminosugars in their structure, while other
members containing deoxystreptamine and amino sugar
in their structure e.g. neomycin, kanamycin, tobramycin,
amikacin, and gentamicin.
 Aminoglycosides that are derived from bacteria of the
Streptomyces genus are named with the suffix -mycin,
whereas those that are derived from Micromonospora are
named with the suffix –micin.
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c. Aminocyclitols
 It is a closely related group to aminoglycosides.
 These contain no amino sugar in their structure e.g.
spectinomycin.
d. Tetracyclines
 A family of closely related antibiotics with four-ringed
structure
e.g.
tetracycline,
chlorotetracycline,
oxytetracycline,
demeclocycline,
methacycline,
doxycycline and minocycline.
e. Polyenes
 These are characterized by possessing a large ring
containing a lactone group and a hydrophobic region
consisting of a sequence of 4-7 conjugated double
bonds.
 Polyenes are poly-unsaturated organic compounds that
contain one or more sequences of alternating double
and single carbon-carbon bonds, e.g. nstatin,
amphotericin.
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f. Macrolides
 These consisting of a macrocyclic lactone ring to which
sugars are attached.
 They
include
spiramycin.
erythromycin,
oleandomycin
and

According to the spectrum of their biological action
a. Antibacterial antibiotics
b. Antifungal antibiotics
c. Antitumor antibiotics
d. Antiprotozoal antibiotics
e. Antiviral antibiotics
a. Antibacterial antibiotics
Narrow spectrum
 Natural penicillins and erythromycin (G +ve)
 Polymyxin (G –ve).
Broad spectrum
 Effective against at least some members of most
genera
 Tetracyclines and chloramphenicol.
Tuberculostatic
Streptomycin, kanamycin and cycloserine.
b. Antifungal antibiotics
Nystatin,
amphotericin
griseofulvin, and candicin.
c. Antitumor antibiotics
d. Antiprotozoal antibiotics
e. Antiviral antibiotics
Actinomycins, mitomycins.
 Fumagillin.
 Helinine.
B,

According to their mode of action
a. Inhibitors of cell wall
synthesis
.
b. Antibiotics acting on cell
membranes
c. Inhibitors of protein
synthesis
d. Inhibitors of nucleic acid
synthesis
e. Inhibitors of folic acid
synthesis (antifolates)
a. Inhibitors of cell wall synthesis
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 The steps of biosynthesis involves many essential
enzymes:
I. Racemes (catalyze change of L-alanine to D-alanine).
II. Synthetase (join two D-alanine molecules forming
the terminal D-alanyl-D-alanine residue of the penta
peptide).
III. Transpeptidases
(catalyze
cross-linking reactions).
transpeptidation
or
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 Penicillins.
 Cephalosporins.
 Bacitracin.
 Vancomycin.
 Teicoplanin.
 Cycloserine.