β-lactam antibiotics are a broad class of antibiotics which contains a β-lactam nucleus in its molecular structure and commonly know antibiotics are penicillin and cephalosporin. These are highly significant drugs which are effective against many serious diseases caused by Streptococcus, Staphylococcus and other bacterial infections. All types of penicillins are Beta-lactam antibiotics are used in the treatment of gram-positive bacterial infections. β-Lactam antibiotics are bactericidal and act by inhibiting the synthesis of the peptidoglycan layer of bacterial cell walls and blocked the bacterial cell division by triggers the activation of bacterial cell wall hydrolases and autolysins. The final transpeptidation step in the synthesis of the peptidoglycan is facilitated by transpeptidases known as penicillin-binding proteins (PBPs).
PENICILLIN: The penicillin skeleton has the molecular formula R-C9H11N2O4S in which R is a variable side chain. All 4 types of penicillins based on their ability to kill various types of bacteria.
1. Natural Penicillins (Penicillin G, Procaine, Penicillin G, Penicillin V, Benzathine) are the first agents in the penicillin family to be introduced for clinical use. They are effective against gram-positive strains of streptococci, staphylococci, and some gram-negative bacteria such as meningococcus. Penicillin V is called orasporin which common administrated drug used for the treatment of streptococcal pharyngitis and it is also useful for anaerobic coverage in patients with oral cavity infections too.
2. PenicillinG is also called Penicillinase-Resistant Penicillins (Cloxacillin, Dicloxacillin, Methicillin, Nafcillin, Oxacillin). The penicillinase-resistant penicillins have a narrower spectrum of activity than the natural penicillins.
3. Aminopenicillins (Ampicillin, Amoxicillin, Bacampicillin). The aminopenicillins were the first penicillins discovered to be active against gram-negative bacteria such as E. coli and H. influenzae. Aminopenicillins are acid-resistant.and administrated orally. Orally administered amoxicillin and ampicillin are used primarily to treat mild infections such as otitis media, sinusitis, bronchitis, urinary tract infections and bacterial diarrhea.
4. Extended Spectrum Penicillins include both alpha-carboxypenicillins (carbenicillin and ticarcillin) and acylaminopenicillins (piperacillin, azlocillin, and mezlocillin). These agents have similar spectrums of activity as the aminopenicillins but with additional activity against several gram negative organisms of the family Enterobacteriaceae and many strains of Pseudomonas aeruginosa. Like the aminopenicillins, these agents are susceptible to inactivation by beta-lactamases. These agents may be used alone or in combination with Aminoglycosides
CEPHALOSPORINS: They are β- lactam antibiotics containing a di- hydrothiazine ring with D-α amino adipic acid as acyl moiety. They are killed the bacterial cell wall by binding with the reaction site of penicillin binding proteins to render the cross linking of bacterial wall. This bactericidal effects of β-lactam antibiotics are achieved through inhibition of the bacterial cell wall synthesis. This transpeptidation reaction is inhibited by β-lactam antibiotics like cephalosporins. In some cases, addition of methoxy group in position A2, cephalosporin stability is enhanced toward β-lactamases. Cephalosporins are widely used antibiotics because of their clinical efficiency and desirable safety profile. They have low toxicity which makes them have a wide use. Therapeutically only semi- synthetic derivatives of cephalosporin and cephamycin are commonly used. Cephalosporin C was discovered in cultures of cephalosporium acremonium, Acremonium chrysogenum, Cephalosoprium spp., Emericellopsis and Paecilomyces.
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Dr. Kirti Rani Sharma,
Assistant Professor (II),
Amity Institute of Biotechnology,
Amity University, sec-125, Gautam Buddha Nagar, Noida-201303 (UP), India.
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