Antibiotics
Antibiotics are widely used in medicine for the treatment of infections caused by susceptible microbiological organisms. Antimicrobial or antibiotic treatment is a well-accepted therapy for fighting microbial infections that takes advantage of the existence of biological processes that are unique to bacteria or fungi, that can be safely inhibited to the detriment of the bacteria, without producing undesired or harmful side effects in the individual receiving such therapy.Several types of antibiotics, classified according to their mechanism of action, are currently employed. The known types of antibiotics include, e.g., cell wall synthesis inhibitors, cell membrane inhibitors, protein synthesis inhibitors, and inhibitors that bind to or affect the synthesis of DNA or RNA. Since the 1940s, a broad range of antibiotics, have become available for the treatment and prevention of bacterially transmitted disease. Penicillin, streptomycin, aureomycin, cephalosporin, bacitracin, erythromycin, novobiocin, methicillin, neomycin, chloramphenicol, kanamycin, chlortetracycline, to name a few - each of these drugs, isolated from microorganisms, has provided a great benefit to the well-being of people and animals the world around. Antibiotics are a class of chemical compounds which are produced by microorganisms, and capable of inhibiting the growth of or destroying bacteria and other microorganisms. Penicillium and Cephalosporium produce beta-lactam antibiotics (e.g., penicillin, cephalosporin, and their relatives). Actinomycetes (e.g., the Streptomyces species) produce tetracyclines, aminoglycosides (e.g., streptomycin and its analogs), macrolides (e.g., erythromycin and its analogs), chloramphenicol, ivermectin, rifamycins, and most other clinically-useful antibiotics that are not beta-lactams. Bacillus species (e.g., B. polymyxa and Bacillus subtilis) produce polypeptide antibiotics (e.g. polymyxin and bacitracin), while B. cereus produces zwittermicin. Chemically, antibiotics have a wide variety of structures and belong to various groups of compounds. Generally, antibiotics have three names, a chemical name, a generic name and a tradename. Glycopeptide antibiotics are characterized by having at least one saccharide group chemically bonded to a rigid peptide structure having a cavity or cleft which acts as a binding site for the substrate used in bacterial cell wall synthesis. The glycopeptide antibiotics are further categorized into various subclasses depending on the identity and interconnections of the amino acids comprising the peptide backbone and the number and substitution pattern of the sugar residues in the molecule. An important class of antibiotics that inhibit gram-positive bacteria are the acidic lipopeptide antibiotics. Generally, acidic lipopeptide antibiotics consist of either a cyclic peptide core or a cyclic depsipeptide core acylated with a lipophilic fragment and have an isoelectric point of less than about pH 7.0. The anthracyclines daunorubicin and doxorubicin (DOX) are some of the more commonly used chemotherapeutic antibiotics. The anthracyclines achieve their cytotoxic effect by several mechanisms, including inhibition of topoisomerase II; intercalation between DNA strands, thereby interfering with DNA and RNA synthesis; production of free radicals that react with and damage intracellular proteins and nucleic acids; chelation of divalent cations; and reaction with cell membranes. Vancomycin antibiotics are amphoteric and strongly levorotatory glycopeptide antibiotics having relatively high molecular weight. Examples of the known vancomycin antibiotics are vancomycin, ristocetin, and actinoidin. Vancomycin has been made into pharmaceutical preparations in a form of its hydrochloride for the therapy of infectious diseases, especially for the therapy of infectious diseases caused by Staphylococcus and by methicillin-resistant strains and has been supplied for oral and parenteral uses as a dried solid preparation filled in aseptic vials or small bottles. Orthosomycins are a group of complex lipophilic oligosaccharide antibiotics that are active against gram positive bacteria including methicillin resistant Staphylococci and/or vancomycin resistant Enterococci. Lipophilic oligosaccharide antibiotics include, for example, eveminomicins, the flambamycins, the avilamycins and the curamycins which contain at least one acidic phenolic hydrogen, at least one orthoester linkage associated with carbohydrate residues and usually a nitrogen-containing group.
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