In our own healthy bodies, the number of bacterial cells is almost equal to the number of human cells [1]. Bacteria* can actually help our body with nutrition, protection, immune response, and other functions [2]. However, some species of bacteria can be harmful.
To fight them, doctors prescribe antibiotics. There are several mechanisms through which antibiotics can kill bacteria [3]. Some of them cause the bacteria to burst by attacking the cell wall or the cell membrane. Others attack the ribosomes**, which are the structures in charge of protein*** synthesis. In consequence, the bacteria can no longer produce new proteins, which are essential for structural and functional processes. The third category of antibiotics targets the bacteria nucleic acids: DNA**** or RNA***** (which contain all their genetic material). Finally, some antibiotics can inhibit the synthesis of folic acid, an important compound for many cellular pathways [4].
As we explained in our latest post, viruses can only replicate by infecting cells [5]. Although antibiotics are useful to kill bacteria, they won’t fight a virus. Instead, antibodies****** and antiviral drugs can be used to treat a viral infection [6]. In the antibody transfusion, the idea is to inject antibodies to help the immune system fight the infection (more information here). On the other hand, antiviral drugs can either target the virus******* itself or focus on the interaction between the virus and the cell that it is infecting [7]. For example, some antiviral drugs inhibit the virus from attaching and entering the cell, or inhibit the enzymes that are relevant for viral replication. Other antivirals alter pathways in the cell so that we can fight the virus more efficiently.
The problem with developing antiviral drugs is that viruses use our cell’s mechanisms to replicate. Thus, it is difficult to find safe and effective drugs that affect the virus without hurting the cell. That is why vaccination is even more important. Vaccination can help prevent infections by preparing our bodies beforehand, so it is an effective strategy against viruses and bacteria! (stay tuned for our next video on how vaccines take advantage of the immune system to protect us).
On some occasions, a person with a viral infection may also receive antibiotics. For example, a COVID-19 patient getting an antibiotic treatment [5]. This is because the patient actually has two infections: a viral and a bacterial infection. When our immune system is compromised, people become more vulnerable, which can lead to multiple infections. However, the antibiotic can only treat the bacterial infection, not the virus.
Because antibiotics and antivirals are respectively for bacteria and viruses, it is important to go to the doctor to ensure that you are taking the right medication. Otherwise, you might take a drug that has no effect on the infection.
*Bacteria - microorganisms invisible to the naked eye that consist of a single cell, though they can group together to form colonies or biofilms. Some bacteria are pathogenic and cause disease, like Salmonella enterica, while others are beneficial to our health, like the ones normally found in the guts.
**Ribosomes - One of the components of cells, it is the structure responsible for producing proteins. It translates the code that an RNA molecule contains into a protein sequence (see genetic code).
***Protein - a molecule that forms the structure and gives function to organisms at the most basic level. Proteins consist of amino acids, which can be combined in different sequences to form different protein structures with different functions in cells.
****DNA - deoxyribonucleic acid, one of the nucleic acids found in living cells. DNA is formed by 4 nucleotides, which can be organized in different sequences and different lengths like letters are organized to form a text. In this case, the “text” formed by the sequence contains the instructions to form a whole organism. DNA is normally found as a paired double strand, in a double helix shape.
*****RNA - Ribonucleic acid, one of the nucleic acids found in cells. It is transcribed from DNA. There are many types of RNAs, some of which can have a specific function controlling or regulating some processes in cells while others (known as messenger RNAs, or mRNAs) carry the genetic information that can be translated into proteins by ribosomes.
******Antibodies - a molecule produced by immune cells that recognizes and binds to another molecule that is foreign to the organism, the antigen. By binding to the antigen, the antibody can tag the foreign molecule for destruction or directly neutralizes it.
*******Virus - it can be considered a very small and basic life form or an aggregate of molecules that is simpler than a cell. They can be found in the environment or inside living organisms. It has to infect a cell and use its machinery to multiply, since it cannot multiply by itself. Viruses consist of nucleic acids (DNA or RNA), a protein capsid that contains the nucleic acids and, sometimes, an external envelope of lipids. The flu, measles, AIDS and Covid-19, for instance, are caused by viruses.
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Written by: Nicole
Edited by: María and Natasha
BioDecoded is a volunteer group committed to sharing accurate scientific information. If you have any questions about this topic, please comment or send them to our email.
References:
Sender, R., Fuchs, S. & Milo, R. Are We Really Vastly Outnumbered? Revisiting the Ratio of Bacterial to Host Cells in Humans. Cell 164, 337-340 (2016). Available at: https://www.cell.com/cell/pdf/S0092-8674(16)00053-2.pdf
Johnson, C. & Versalovic, J. The Human Microbiome and Its Potential Importance to Pediatrics. PEDIATRICS 129, 950-960 (2012). Available at:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3340594/
Kapoor, G., Saigal, S. & Elongavan, A. Action and resistance mechanisms of antibiotics: A guide for clinicians. Journal of Anaesthesiology Clinical Pharmacology 33, 300 (2017). Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5672523/
Fernández-Villa, D., Aguilar, M. & Rojo, L. Folic Acid Antagonists: Antimicrobial and Immunomodulating Mechanisms and Applications. International Journal of Molecular Sciences 20, 4996 (2019). Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6829374/
What’s the difference between bacteria and viruses?. Imb.uq.edu.au (2021). Available at: https://imb.uq.edu.au/article/2020/04/difference-between-bacteria-and-viruses (Accessed: 19th June 2021)
Adamson, C. et al. Antiviral drug discovery: preparing for the next pandemic. Chemical Society Reviews 50, 3647-3655 (2021). Available at: https://pubs.rsc.org/en/content/articlelanding/2021/cs/d0cs01118e#!divAbstract
Kausar, S. et al. A review: Mechanism of action of antiviral drugs. International Journal of Immunopathology and Pharmacology 35, 205873842110026 (2021). Available at: A review: Mechanism of action of antiviral drugs – PubMed (nih.gov)
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