The term antibiotic was derived from the word “antibiosis” which actually means “against life”.
Antibiotics were thought to be organic compounds produced by microorganisms which are toxic to other microorganisms. An antibiotic was defined as a substance that is produced by one microorganism or of biological origin which at low concentrations can inhibit the growth of, or kill other microorganisms.
The discovery and development of the beta–lactam antibiotics is the most powerful, important and famous achievement of modern science and technology. Penicillin was the first beta lactam antibiotic that was discovered by an English Bacteriologist, late Sir Alexander Fleming who accidentally discovered the antibiotic Penicillium notatum from a fungus that inhabit soil, which was first reported in 1929. Beta lactam antibiotics are cell wall synthesis inhibitors.
The first antibiotic that belongs to class of macrolide was discovered and isolated in 1952 by J. M. McGuire as a metabolic product of a soil inhabiting fungus Saccharopolyspora erythraea. This fungus was known as Streptomyces erythraeus that belongs to the genus Saccharopolyspora of actinomycete bacteria. Macrolides are protein synthesis inhibitors.
Antibiotics are generally classified on the basis of theirmolecular structures mode of action and spectrum of activity androute of administration (injectable, oral and topical). Antibiotics that possess same structural class generally shows similar pattern of effectiveness, toxicity and allergic-potential side effects.
Beta lactam antibiotics are further classified into
Βeta lactam antibiotics are the antibiotic agents that contain a beta-lactam ring in their molecular structure. A beta lactam ring is a four membered lactam (cyclic amide) that contains a 3-carbon and 1-nitrogen which is highly reactive
The general chemical structure of macrolides is characterized by a large lactone ring containing from 12 to 16 atoms to that are attached, through a glycosidic linkage to one or more sugars.
SPECTRUM OF ACTIVITY
Beta Lactams includes penicillins and cephalosporins, are narrow spectrum antibiotics, which are highly effective against the Gram-positive genera Streptococcus, Gonococcus, and Staphylococcus.
Macrolides are highly active against gram-positive except enterococci and some gram-negative bacteria. They are also effective against Mycoplasma pneumoniae, Treponema pallidum, Bordetella pertussis, Chlamydia trachomatis, Chlamydophila pneumoniae, Legionella spp., Campylobacter spp.
Beta lactam antibiotic interfere with synthesis of bacterial cell wall, and in the process either kills or inhibits the growth of bacteria. More succinctly, certain bacterial enzymes termed penicillin-binding protein (PBP) are responsible for cross linking peptide units during synthesis of peptidoglycan. Members of beta-lactam antibiotics are able to bind themselves to these PBP enzymes, and in the process, they interfere with the synthesis of peptidoglycan resulting to lysis and cell death.
The mechanism of action of macrolides is inhibition of bacterial protein biosynthesis, they bind to 50S ribosome and inhibit protein synthesis and they are thought to do this by inhibiting peptidyl transferase from adding the growing peptide attached to transfer RNA to the next amino acid as well as inhibiting ribosomal translation.
The resistance to beta lactam antibiotic may be caused due to the following reasons
The resistance to macrolides may be caused by following mechanisms