Antibiotic resistance is not a modern incidence. Resistant bacteria are ancient. Antibiotics are discovered more than 70 years ago but resistant bacteria existed before the very beginning of human civilization. At the initial stage of antibiotic era, resistant bacteria was not a matter of concern. Now it is a big headache for the scientists. Antibiotic misuse or over use caused this problem.
Then where does it come from……?
If you ask this question……the common answer is ‘mutation’ which is caused by antibiotic misuse. It means, at the beginning bacteria was not resistant but antibiotic overuse caused mutation in the gene which are responsible for the encoding of different proteins.
Actually this idea is partially incorrect. Let us give an example: a drug which is metabolized by any particular enzyme in our body but this enzyme differs slightly from person to person due to few reasons including single-nucleotide polymorphism. Hence, drug metabolism also differs from person to person. Resistant bacteria are common in normal bacterial population, this is something like intra species variation.
Antibiotic resistance can be explained by ‘Theory of Natural Selection‘ which was popularized by Charles Darwin. According to this theory any environmental incidence which is a threat to the survival of any living species, causes ‘Selection Pressure” which results in the increased reproduction of the stronger members of that vulnerable species which is known as ‘Survival of the fittest‘. The transfer of the gene could be vertical or horizontal. It means the resistant genes are not recently created. These genes are present from the ancient time but when ‘Selection Pressure’ is caused by antibiotic misuse or overuse, these genes were transferred vertically or horizontally from the survived bacteria.
Or even resistant nature could be very common. For example: all bacteria may produce penicillinase. Some bacteria can produce penicillinase in greater amount and hence these are resistant to penicillin. On the other hand some bacteria produce penicillinase in small amount and these are susceptible to penicillin.
Antibiotic resistant gene could be revert back to the main wild type gene by reducing the use of any particular antibiotic. There are so many evidence of this phenomena. Chloramphenicol resistance has been reduced in Nepal. Resistant genes may be able to fight back antibiotics exposure but in the most cases resistant genes are not as good as wild type genes for their normal biological function. Hence when antibiotic exposure is reduced, there will be no need of these less efficient resistant genes which will be eventually replaced by the wild type. It means those antibiotics which are not useful at this moment, we can use those after few decades.
- Stressed Bacteria Become Resistant To Antibiotics (medicalnewstoday.com)
- Antibiotic Resistance (sciencedaily.com)
- Antibiotic Resistance (detectingdesign.com)