BETA-LACTAM ANTIBIOTICS

Beta-Lactam Antibiotics

Beta-Lactam Antibiotics

Introduction

Beta-Lactam Antibiotics are an important group of drugs, prescribed for various common infections that affect a majority of the population around the world. They have been around for almost more than 50 years. Manufacturing of beta-lactams initially had low product yield but now its produced around the world and contributes to nation's GDP .Some of the notable members includes Penicillin (Amoxicillin, Benzyl Penicillin, Ampicillin) and Cephalosporins (Ceftazidime, Cefuroxime, Ceftriaxone). Their antibiotic activity ranges from narrow spectrum to broad spectrum with a wide variety of drugs for specific or general treatment. In this paper, we will discuss about beta-lactams' Mode of Action, chemical structure, resistance, dosage forms and doses, toxicity and finally a brief review about alternatives in conclusion.

Discussion

Mode of Action

The name Beta-Lactam refers to the presence of the beta-lactam ring in these compounds which inhibits cell wall synthesis. Cell wall of bacteria consists of peptidoglycans and provides rigidity and stability to the cell. It comprises of amino sugar chains of N-acetylglucosamine and N-acetylmuramic acid. Upon completion of cross linking of glycan chains, transpeptidation i.e. transfer of amino acids from one peptide chain to another (Farlex, 2012) occurs. It is this last step which is inhibited by the beta-lactam antibiotics and stops the growth of bacteria by stopping cell wall growth resulting in the breakdown of cell wall and finally, cell lysis (Goodman and Gilman, 2010). This is one of the mechanisms explained, research is going on about other mechanisms, yet it is unclear.

Chemical Structure

Beta-Lactam antibiotics give action due to their chemical structure. It's a 4 member ß-lactam ring which is joined to a five membered heterocyclic ring (Penicillin or penams) or six membered heterocyclic ring (Cephalosporin or cephems). The heterocyclic ring in case of penams has a double bond between C-2 and C-3 that is saturated or unsaturated and at C-3 and C-4 in case of cephems. These 5 or 6 member rings are responsible for the antimicrobial activity of these antibiotics, overcome the defences of bacteria and eliminate them in process (Dalhoff et al, 2006).

Figure 1 Source: http://www.cram.com/flashcards/antibacs-i-anaerobes-opporinfections-3059782

Resistance

Beta lactams are one of the most susceptible groups to resistance development by microorganisms. Resistance is reported as early as 40's by Alexander Fleming himself. Nosocomial infections are another problem that arises due to resistance by the bacteria, which results in suffering or worse, death.

Resistance is classified into 2 types: Active and Passive. Here, active means that resistance developed as a result of evolution in mechanism to counter the drug attack and as for passive, its general process of adaption which may or may not be linked to a particular class of antibiotic. While these are the ways that resistance develops, the breakdown of antibiotic happens either by hydrolysis or by the development of ß-lactamases. In other words, the molecule is broken by the enzymes. Many antibiotics can be made inactive by hydrolysis due to the presence of esters and amides in their chemical bonds. Amidases are such enzymes that cleave the beta-lactam ring in cephalosporins and ...