What is the Difference Between Beta-Lactam and Non-Beta-Lactam Antibiotics

The main difference between beta-lactam and non-beta-lactam antibiotics is that beta-lactam antibiotics contain a highly reactive beta-lactam ring, whereas non-beta-lactam antibiotics lack the beta-lactam ring.

Beta-lactam and non-beta-lactam antibiotics are two antibiotic types that have different structures. They can be bactericidal and bacteriostatic. 

Key Areas Covered

1. What are Beta-Lactam Antibiotics
– Facts, Features, Behaviour
2. What are Non-Beta-Lactam Antibiotics
– Facts, Features, Behaviour
3. Similarities Between Beta-Lactam and Non-Beta-Lactam Antibiotics
– Outline of Common Features
4. Difference Between Beta-Lactam and Non-Beta-Lactam Antibiotics
– Comparison of Key Differences

Key Terms 

Beta-Lactam Antibiotics, Non-Beta-Lactam Antibiotics

What are Beta-Lactam Antibiotics

Beta-lactam antibiotics are the most common type of antibiotics in the world. These antibiotics share a common feature which is the presence of a beta-lactam ring (3-carbon and 1-nitrogen ring) that is highly reactive. There are five classes of beta-lactam antibiotics:

• Penicillins: They contain lactam plus thiazolidine ring and other ringside chains. This group includes natural penicillins, aminopenicillins, beta-lactamase-resistant agents, carboxypenicillins, and ureidopenicillins.
• Cephalosporins: They contain a nucleus of 7-aminocephalosporanic acid and other side chains.
• Carbapenems: They contain a beta-lactam ring along with carbapenem.
• Monobactams: They only contain a beta-lactam ring.
• Beta-lactamase inhibitors – They inhibit serine-beta-lactamases.
  
  

  Figure 1: Penicillin

Moreover, bacteria are resistant to beta-lactam antibiotics in many ways. They inactivate beta-lactam antibiotics by the production of beta-lactamase enzyme. Also, they decrease the penetration to the target site, alteration of the target site, and effluxion from the periplasmic space to become resistant to beta-lactam antibiotics. However, the mechanism of action of the beta-lactam antibiotics is by inhibiting the cell wall synthesis of bacteria.

What are Non-Beta-Lactam Antibiotics

Non-beta-lactam antibiotics are other antibiotics that lack the beta-lactam ring. There are four modes of action of non-beta-lactam antibiotics against bacteria. They can inhibit the protein synthesis inside the bacterial cell. Macrolides such as erythromycin inhibit the formation of peptide bonds in bacteria. Also, some selective antibacterial drugs, such as tetracycline, selectively bind bacterial ribosomes to inhibit protein synthesis.

Figure 2: Tetracycline

Meanwhile, some non-beta-lactam antibiotics inhibit the synthesis of nucleic acids. There are two types of non-beta-lactam antibiotics; RNA inhibitors and DNA inhibitors. For example, rifampicin inhibits RNA synthesis. 

Moreover, some non-beta-lactam antibiotics disrupt the cell membrane of bacteria. Examples of such antibiotics are polypeptide gramicidin D and cyclic polypeptide gramicidin S. They transfer ions through the bacterial cell wall that kills bacteria. Conversely, some non-beta-lactam antibiotics serve as antimetabolites. It stops life-sustaining biochemical reactions such as the metabolic reactions of bacteria. For example, sulfonamides control the production of tetrahydrofolate by mimicking PABA, a metabolite. 

Similarities Between Beta-Lactam and Non-Beta-Lactam Antibiotics

• Beta-lactam and non-beta-lactam antibiotics are two antibiotic types that act against bacteria. 

Difference Between Beta-Lactam and Non-Beta-Lactam Antibiotics

Definition

Beta-lactam antibiotics refer to antibiotics that contain a beta-lactam ring in their chemical structure. In contrast, non-beta-lactam antibiotics refer to a common alternative to penicillin with no beta-lactam ring in the chemical structure. 

Function

Beta-lactam antibiotics inhibit the synthesis of bacterial cell walls. In contrast, non-beta-lactam antibiotics inhibit protein and nucleic acid synthesis, disrupt cell membranes, and function as antimetabolites of bacteria. 

Examples

Penicillin, cephalosporins, carbapenems, monobactams, and beta-lactamase inhibitors are examples of beta-lactam antibiotics, while macrolides, rifampicin, gramicidin D, and sulfonamides are examples of non-beta-lactam antibiotics.

Conclusion

In brief, beta-lactam and non-beta-lactam antibiotics are two antibiotics that act against bacteria. Beta-lactam antibiotics contain a beta-lactam ring in the structure. Significantly, they inhibit the growth of bacterial cell walls. The five types of beta-lactam antibiotics include penicillin, cephalosporins, carbapenems, monobactams, and beta-lactamase inhibitors. In comparison, non-beta-lactam antibiotics do not contain the beta-lactam ring. Also, they act against bacteria by inhibiting the synthesis of proteins, nucleic acid synthesis, disrupting cell membranes, and functioning as antimetabolites of bacteria. Examples of non-beta-lactam antibiotics include macrolides, rifampicin, gramicidin D, and sulfonamides. Therefore, the main difference between beta-lactam and non-beta-lactam antibiotics is their function. 

References:

1. Pandey N, Cascella M. Beta-Lactam Antibiotics. [Updated 2022 Sep 26]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-.Kairys N, Garg M. Gardnerella. [Updated 2022 Aug 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-.
2. Non-beta-lactam antibiotics. FutureLearn. (2022, October 25). https://www.futurelearn.com/info/courses/everyday-chemistry/0/steps/22317

Image Courtesy:

1. “Penicillin core” By Yikrazuul – Own work (Public Domain) via Commons Wikimedia
2. “Tetracycline skeletal” By Vaccinationist – Own Work (Public Domain) via Commons Wikimedia