The Top 20 Antibiotics

The top 20 notable antibiotics that have made significant contributions to the field of medicine are described here. They are defined according to FoodWrite’s rating of their impact on treatment. I daresay the list will change with time but this was the situation based on commercial production levels in 2019.

1. Penicillin: Penicillin was the first antibiotic discovered by Alexander Fleming. It inhibits bacterial cell wall synthesis and is effective against a wide range of bacterial infections.
2. Cephalosporins: Cephalosporins are a group of antibiotics that share a similar structure to penicillin. They are effective against Gram-positive and Gram-negative bacteria and are commonly used for various infections.
3. Tetracycline: Tetracycline antibiotics inhibit bacterial protein synthesis and are effective against a broad spectrum of bacteria. They are commonly used for respiratory, urinary, and skin infections.
4. Erythromycin: Erythromycin belongs to the macrolide group of antibiotics and inhibits bacterial protein synthesis. It is effective against Gram-positive bacteria and is commonly used for respiratory tract infections.
5. Vancomycin: Vancomycin is a glycopeptide antibiotic used to treat serious infections caused by Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA).
6. Aminoglycosides: Aminoglycosides, such as gentamicin and streptomycin, inhibit bacterial protein synthesis. They are used to treat severe infections caused by Gram-negative bacteria.
7. Fluoroquinolones: Fluoroquinolones, including ciprofloxacin and levofloxacin, inhibit bacterial DNA replication and are effective against a broad range of bacteria. They are commonly used for urinary tract and respiratory tract infections.
8. Sulfonamides: Sulfonamides, such as sulfamethoxazole, inhibit bacterial folate synthesis. They are often used in combination with trimethoprim to treat urinary tract infections and respiratory tract infections.
9. Clindamycin: Clindamycin is a lincosamide antibiotic that inhibits bacterial protein synthesis. It is effective against both Gram-positive and anaerobic bacteria and is used for skin and soft tissue infections.
10. Rifampin: Rifampin is a rifamycin antibiotic used primarily to treat tuberculosis and other mycobacterial infections. It inhibits bacterial RNA synthesis.
11. Linezolid: Linezolid is an oxazolidinone antibiotic used for the treatment of serious infections caused by Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA).
12. Metronidazole: Metronidazole is an antibiotic used primarily for the treatment of anaerobic bacterial infections, as well as certain protozoal infections. It works by damaging the DNA of the microorganisms.
13. Carbapenems: Carbapenems, such as meropenem and imipenem, are broad-spectrum antibiotics effective against a wide range of bacteria, including Gram-positive, Gram-negative, and anaerobic bacteria.
14. Azithromycin: Azithromycin is a macrolide antibiotic similar to erythromycin. It is commonly used to treat respiratory tract infections, as well as certain sexually transmitted infections.
15. Amoxicillin: Amoxicillin is a penicillin antibiotic used for various bacterial infections, including respiratory tract infections, ear infections, and urinary tract infections.
16. Doxycycline: Doxycycline is a tetracycline antibiotic used to treat a variety of infections, including respiratory tract infections, acne, and certain sexually transmitted infections.
17. Meropenem: Meropenem is a carbapenem antibiotic used for serious bacterial infections, including intra-abdominal infections, pneumonia, and meningitis.
18. Imipenem: Imipenem is another carbapenem antibiotic effective against a wide range of bacteria, including multidrug-resistant strains. It is commonly used for severe infections.
19. Clarithromycin: Clarithromycin is a macrolide antibiotic similar to erythromycin. It is used to treat respiratory tract infections, as well as certain bacterial infections associated with stomach ulcers.
20. Daptomycin: Daptomycin is a lipopeptide antibiotic used for the treatment of skin and soft tissue infections caused by Gram-positive bacteria, including MRSA.

These antibiotics have played vital roles in the treatment of bacterial infections and have saved countless lives. However, it’s important to note that the use of antibiotics should be judicious to prevent the development of antibiotic resistance and preserve the effectiveness of these medications.

Production of Antibiotics

Most antibiotics are produced by fermentation. They are good examples of secondary metabolites produced when the fermenting microorganism begins to reach the end of the lag phase.

The production of antibiotics involves a complex process that typically utilizes fermentation techniques. Here’s a general overview of the production steps:

1. Strain Selection: The first step in antibiotic production is the selection of a suitable microorganism strain that naturally produces or can be engineered to produce the desired antibiotic compound. The chosen strain should have high productivity, stability, and the ability to grow under controlled conditions.
2. Inoculum Development: The selected strain is cultivated in a small-scale culture known as the inoculum. This step involves providing optimal growth conditions, such as a nutrient-rich medium, proper temperature, and aeration, to promote the growth and multiplication of the microorganism.
3. Fermentation: The inoculum is then transferred to a larger fermentation vessel, often called a bioreactor. The bioreactor provides a controlled environment for the growth of the microorganism on a larger scale. The medium in the bioreactor contains the necessary nutrients for the microorganism to thrive and produce the antibiotic. Factors like temperature, pH, oxygen levels, and agitation are carefully controlled to maximize antibiotic production.
4. Antibiotic Production: As the microorganisms grow and multiply in the bioreactor, they metabolize nutrients and produce the desired antibiotic compound as a secondary metabolite. The antibiotic is typically produced during the stationary phase of growth or as the microorganisms transition to a different growth phase.
5. Harvesting: Once the antibiotic production reaches its peak, the fermentation broth containing the microorganisms and the antibiotic is harvested from the bioreactor. The broth may go through various separation processes, such as filtration or centrifugation, to separate the solid biomass of the microorganisms from the liquid portion.
6. Purification: The harvested broth undergoes purification to isolate and purify the antibiotic compound. Purification steps may include filtration, chromatography, crystallization, and other separation techniques to remove impurities, byproducts, and unwanted compounds.
7. Formulation and Packaging: After purification, the antibiotic compound is formulated into a suitable form for administration, such as tablets, capsules, liquids, or injectables. The formulation process involves combining the antibiotic with other ingredients to achieve the desired dosage form and stability. The final product is then packaged in appropriate containers under controlled conditions.

Typical examples of antibiotic produced by this method include penicillin.

Immobilised cells

One method to ensure cells are directed to produce particular types of antibiotic is through cell immobilization.

In one example, whole microbial cells of Streptomyces clavuligerus were immobilised into water-soluble polyacrylamide that was partially substituted with acylhydrazide groups (Freeman & Aharonowitz, 1981). This is a cephalosporin producer.

Whole cells of  Bacillus have also been immobilised in polyacrylamide gel for the production of bacitracin (Morikawa et al., 1980).

Other cells have been immobilised for the production of the mycotoxin, patulin which is also an antibiotic in its own right. Patulin is highly problematic in fruit juice production, especially in apple juice.

It’s important to note that the specific details of antibiotic production can vary depending on the type of antibiotic, the microorganism used, and the manufacturing process employed by each pharmaceutical company. The production of antibiotics requires strict quality control measures to ensure safety, purity, and efficacy of the final product.

References

Freeman, A., & Aharonowitz, Y. (1981). Immobilization of microbial cells in crosslinked, prepolymerized, linear polyacrylamide gels: antibiotic production by immobilized Streptomyces clavuligerus cells. Biotechnology and Bioengineering, 23(12), pp. 2747-2759 (Article).

Morikawa, Y., Karube, I., & Suzuki, S. (1980). Continuous production of bacitracin by immobilized living whole cells of Bacillus sp. Biotechnology and Bioengineering, 22(5), pp. 1015-1023 (Article).

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