Aminoglycosides PCI syllabus. from Prof. P. Ravisankar..pdf

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Neomycin:
Waksman and Lechevalier isolated (produced) neomycin in 1949 from Streptomyces fradiae.
It is a mixture of closely related substances “neomycin complex” is Neamine (originally
designated Neomycin A
Neomycin B
Neomycin C.
S. fradiae also elaborates on another antibiotic, fradicin, which has some antifungal
properties but no antibacterial activity. This substance is not present in “pure” neomycin.
Neamine may be obtained by methanolysis of neomycin B and C, during which the
glycosidic link between deoxystreptamine and D-ribose is broken.
Therefore, neamine is a combination of deoxystreptamine and Neosamine C.
Neosamine B, differs from neosamine C in its stereochemistry in which the orientation of the
6- aminomethyl group is inverted to the 6-amino-6-deoxy-D alpha glucosamine in neosamine
C. In both instances, the glycosidic links were assumed to be alpha.

Clindamycin
Clindamycin is a semisynthetic derivative of lincomycin, a natural antibiotic produced by
the actinobacterium Streptomyces lincolnensis. It is an antibiotic medication used for the
treatment of a number of bacterial infections, including osteomyelitis (bone) or joint
infections, pelvic inflammatory disease, strep throat, pneumonia, acute otitis media (middle ear
infections), and endocarditis.
It can also be used to treat acne, and some cases of methicillin-resistant Staphylococcus
aureus (MRSA).
In combination with quinine, it can be used to treat malaria.

Mechanism of action: Clindamycin has a primarily bacteriostatic effect. At higher concentrations,
it may be bactericidal. It is a bacterial protein synthesis inhibitor by inhibiting ribosomal
translocation. It does so by binding to the rRNA of the bacterial 50S ribosome subunit.
2-chloro-3,4,5-trihydroxy-6-(methylsulfanyl)tetrahydro-2H-
pyran-2-yl]propyl}-1-methyl-4-propylpyrrolidine-2-carboxamide

STYPTOMYCIN(STN)
Streptomycin is the first aminoglycoside antibiotic which was isolated from the
actinomycetes bacteria Streptomyces griseus and several related soil microorganisms. 
Streptomycin was first discovered in 1943 by Selman abraham wakesman and received a
Nobel prize in 1952. It was introduced in 1943 primarily for the treatment of tuberculosis.
It works by blocking the ability of 30S ribosomal subunits to make proteins, which results
in bacterial death.
Chemistry of streptomycin:
Streptomycin is made up of 3 basic structural units called
Streptidine (a diguanidino compound)
Streptose (a aldose sugar)
N-methyl-L-glucosamine unit.

The two guanidino groups attached to the streptidine exhibits strong basic nature.
SAR of streptomycin
Reduction of aldehyde to alcohol results in a compound dihyrostreptomycin activity is similar
to streptomycin but producing severe deafness.
2. Oxidation of aldehyde group to a (oxime,semicarbazone,phenylhydrazone) Schiff base
derivatives results in inactive analogues.
3. Oxidation of –CH3 group in α-streptose to a methylene hydroxy gives an active analogous
but has no advantage over STM.
4. Modification of amino methyl group in the glucosamine by demethylation and replace by
larger alkyl groups reduces activity.
5. In N-methyl-L-glucosamine( –NHCH3 group) is very essential for the acivity.
6. Guanidino groups streptidine ring are essential .Replacement of guanidino groups reduces
the antibacterial activity.
7. In N-methyl –L-glucosamine the “N” atom should be secondary amine.

Uses:
Streptomycin is an antibiotic medication used to treat a number of bacterial
infections,[3]
including tuberculosis, Mycobacterium
avium complex, endocarditis, brucellosis, Burkholderia infection, plague, tularemia, and rat bite
fever.[3]
For active tuberculosis it is often given together with isoniazid, rifampicin,
and pyrazinamide.
In veterinary medicine, streptomycin is the first-line antibiotic for use against gram
negative bacteria in large animals (horses, cattle, sheep, etc.). It is commonly combined with
procaine penicillin for intramuscular injection

Mechanism of Tetracyclines: Tetracyclines bind reversibly to the 30s subunit of the bacterial
ribosome. This action prevents to the amino acyl t-RNA to the accepter site of mRNA
ribosome complex, thereby peptide chain fails to grow and inhibiting bacterial protein
synthesis.
Aminoglycoside toxicity:
1. Nephrotoxicity
2. Ototoxicity
3. Neuromuscular paralysis

Mechanism of action: Chloramphenicol is bacteriostatic (that is, it stops bacterial growth). 
It is a protein synthesis inhibitor  Chloramphenicol binds to the 50S subunit of ribosomes and
appears to act by inhibiting the movement of ribosomes along mRNA, probably inhibiting the
peptidyl transferase reaction by which the peptide chain is extention.

Side effects of chloramphenicol: Abdominal pain; Bloating; Blood disorders which may be
serious; Diarrhoea; Fatigue; Fever; Headache; Nausea and vomiting
2. Newburn babies with immature liver function can get a serious side effect where the skin
develops a grey colour and there is circulatory collapse (grey syndrome).
3. This drug is quite toxic to bone marrow (suppression of bone marrow). The nitro group is
suspected to be responsible for this, although intestinal bacteria are capable of reducing this
group to an amino group.  aplastic anaemia.
Uses: Chloramphenicol is an antibiotic used to treat a variety of bacterial infections
 In some regions in the world chloramphenicol is the drug of the choice for the treatment of
typhoid when more expensive drugs cannot be afforded.
 It is also widely used against eye and ear infections.
 Meningitis, Anthrax, Brucellosis  Burkholderia Infections (in cystic fibrosis patients,
immunocompromised patients)  Chlamydial Infections 

Clostridium Infections  Vibrio (Infections Treatment of cholera caused by Vibrio cholerae)
 Ehrlichiosis, Plague, Rat-bite Fever
 Rickettsial Infections, Haemophilus influenzae infection  Chloramphenicol treats only
bacterial eye infections. Chloramphenicol will not work for other types of eye infections 
anti-infective ear preparations.
Aminoglycosides: Spectrum of Antimicrobial Activity:
Aminoglycosides are broad-spectrum antibiotics effective in: 1. Systemic Infections caused
by aerobic G(-) bacillus (klebsiella, proteus, Enterobacter’s).
2. Tuberculosis, Brucellosis, Tularaemia and yersinia infections.
3. Amoebic dysentery, shigellosis and salmonellosis.
4. Pneumonia and urinary infections caused by Pseudomona aeroginosa.  G(+) and G(-)
aerobic cocci except staphylococci and anaerobic bacteria are less susceptible.

Aminoglycosides PCI syllabus. from Prof. P. Ravisankar..pdf

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