Download Practical applications of Antibiotics - KSU - Home

Dr. Saba Abdi
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Selective toxicity with minimal side effects to
host
Easy to tolerate without a complex drug
regimen
Bactericidal rather than bacteriostatic
Narrow spectrum
Low cost
Stable(shelf life)
Adequate bioavailability
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Antibiotics can be :
• Antibacterial
• Antiviral
• Antifungal
• Antiprotozoal
• Cancerostatic
• Coccidiostatic
• Antihelmintic
• Insecticidal
• Herbicidal
• Immunosuppressive
• Diabetogenic
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Beta lactum antibiotics are chemicals that contain the
4-membered beta lactum ring. They are produced by
the fungus molds Penicillium and Cephalosporium.
These antibiotics inhibit the last step in the
bacterium's cell wall synthesis. Beta lactum
antibiotics are useful against Gram-positive bacteria.
There are several kinds of beta lactum antibiotic:
• Natural Penicillins are produced by fermentation of
the fungus Penicillium notatum chrysogenum. They
include Pencillin G and Penicillin V. They will kill
streptococcus, gonococcus and staphylococcus. They
are usually not effective against Gram-negative rodshaped bacteria.
• Cephalolsporins are similar to penicillins and are
made from a species of Cephalosporium. They are
used as penicillin substitutes, and in surgical
prophylaxis.
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Semisynthetic penicillins were first used in 1959.
A mold produces the main part of the molecule,
which is then altered chemically. These
antibiotics are usually constructed to have certain
advantages over natural penicillins.
Some types of semisynthetic penicillin:
• Amoxycillin and Ampicillin are useful not only
on Gram-positive bacteria, but also on some
Gram-negative bacteria.
• Clavamox, also called augmentin, is prepared by
adding chavulanic acid to amoxycillin. Clavulanic
acid is made from Streptomyces clavuligerus.
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Aminoglycosides are products of Spectromyces griseus.
They are protein synthesis inhibitors binding to bacterial
ribosomes to prevent the initiation of protein synthesis.
They can be used against a wide variety of both Gram-positive
and Gram-negative bacteria.
Aminoglycoside usage has been limited because prolonged use
has been found to cause kidney damage and injury to the
auditory nerves, leading to deafness.
Some examples of Aminoglycosides are: Streptomycin has its
primary use for treating tuberculosis patients.
Gentamicin is used against many strains of Grma-positive and
Gram-negative bacteria, including Pseudomonas aeruginosa
Kanamycin is a complex of three different antibiotics. It is
effective against many gram-positive bacteria, including
penicillin-resistant staphlococci, even at low concentrations.
Tombramycin, along with gentamicin, are the principal
antibiotics used for treatments against Pseudomonas infections.
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Tetracyclines are a family of eight antibiotics, all
products of Sptromyces. Some of these can now be
produced synthetically.
 Tetracyclines block protein synthesis on isolated
ribosomes. It concentrates in certain types of ribosomes
possesed only by bacteria, so it is not toxic to the
animal. Because of their extremely low toxicity, they
were overused in the medical community, and now
there is widespread resistance to tetracyclines.
However, they are still useful in treatment of some
diseases, such as Lyme disease.
 Some examples of tetracyclines are:
Tetracycline
Chlortetracycline
Doxycycline is a semisynthetic tetracycline
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Macrolides are produced by Streptomyces
erythreus.
• Their chemical structures contain large lactone
rings linked through glycoside bonds with amino
sugars.
• Macrolides are inhibitors of protein synthesis.
They are effective against Gram-positive bacteria
and most Gram-negative bacteria, Neissera,
Legionella, and Haemophilus, but not
Enterobacteriaceae.
• The most important macrolides are:
Erythromycin
Oleandomycin
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Polyenes
Variotin
Griseofulvin
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Actinomycin
Mitocin C
Daunomycin
Adriamycin
Carminomycin
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Antibiotic
Disease
Fusaric acid
Parkinson’s disease
D-penicillamine
Rheumatoid artheritis, multiple
sclerosis, chronic active hepatitis,
pulmonary fibrosis and heavy
metal poisoning
Candicidin
Hypercholesterolaemia
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Indirect effect: Alteration of ecological
balance of the normal microflora or induction
of allergic or hypersensitivity reaction.
Direct effects(toxicity): ototoxicity,
neuromuscular blockade, neurological
toxicity, nephrotoxicity , haematological
toxicity, hepatotoxicity , gastrointestinal
toxicity, cutaneous toxicity.
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Used to treat infections, to increase growth
and to improve feed utilization.
Examples:
Penicilline and streptomycin are used to
prevent infection during artificial
insemination of cattle.
Monensin is added to cattle feed to cause
growth increase and improve feed
utilization.
Tetracycline is added to fish feed to prevent
bacterial infection.
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Antibiotics are used as pesticides, herbicides,
growth regulators and for short term
conservation of food.
Examples:
Thuringin- it is a nucleoside exotoxin is an
insecticidal antibiotic
Polunactin is used as an acaricide (pesticide).
Herbimycin is used as a herbicide
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