Some bacteria can develop resistance to these types of drugs, becoming a serious threat to our health.
Even so, just as there are bacteria that establish symbiotic relationships with humans, others benefit from them based on their damage, known as parasitic species. These cause damage by multiplying inside the body, and can even spread throughout the body and generate serious conditions such as the dreaded septicemia. Therefore, the use of antibiotics is essential for any type of bacterial infection.
Despite the effectiveness of these drugs, the World Health Organization places antibiotic resistance as one of the greatest threats globally. Do you know what antibiotic resistant bacteria are? Here we tell you everything you need to know about them.
Antibiotic-resistant bacteria: a growing threat
In order to understand the seriousness of this evolutionary mechanism, it is first necessary to understand what a bacterium is as a functional unit and what the specific effect of the antibiotic itself is.
1. An effective drug or not?
Bacteria are unicellular prokaryotic microorganisms, that is, they are composed of a single cell capable of self-replication by itself to give rise to two identical copies of the parent. To do this, they have a circular DNA chain, ribosomes (devices for protein synthesis) and a cell wall that gives them resistance to inclement weather. Antibiotics work in various ways:
- Some act on ribosomes . These become unable to synthesize proteins, which prevents the growth and development of the bacteria.
- Others inhibit cell wall synthesis and repair , making replication impossible.
- Certain antibiotics inhibit DNA replication , which prevents the duplication of genetic information to give rise to new bacteria.
- Some inhibit metabolic processes essential for cell function, such as the synthesis of folic acid.
As we can see, the task of antibiotics is to make pathogenic bacteria vulnerable and limit their exponential growth, so that the immune system of the invaded organism can take care of them. Even so, there are certain cases in which this task is complicated.
2. How does resistance happen?
Antibiotic-resistant bacteria have various ways of coping with these drugs. We have to bear in mind that we are dealing with microorganisms with an incredible adaptive capacity. Before entering fully into the mechanisms, it is necessary to differentiate the types of resistance:
- Natural resistance : certain bacteria that lack the target organ that the antibiotic attacks. For example, the lack of a cell wall.
- Acquired resistance : it can occur by mechanisms of genetic mutation at the chromosomal level or by gene transfer.
Plasmids are autonomous DNA molecules present in bacteria. They replicate independently, and contain genetic information that can be transmitted from one organism to another in different ways (by conjugation). This is what we refer to when we talk about “gene transfer”, since a specific plasmid can have a genetic modification that gives the bacteria resistance to the antibiotic, and this can replicate and integrate into other members of the colony.
It is necessary to emphasize that these mechanisms are neither conscious nor voluntary. Mutations occur randomly in all living things, and by chance, they sometimes favor resistance to a series of inclement conditions. Thus, natural selection encourages the new, more successful mutants to proliferate while the less adapted ones end up disappearing. Now yes, we will explain in a general way how bacteria obtain these resistances.
2.1. Inactivation of antibiotics by enzymes
DNA contains all the information necessary for protein synthesis , both in bacteria and in other living organisms. Enzymes are special proteins that catalyze various biochemical processes. Thus, when a mutation occurs, some of these new enzymes may have deleterious capacities against the antibiotic.
A clear example of this are beta-lactamases, capable of destroying the beta-lactam ring of various antibiotics such as penicillin or cephalosporins, completely inactivating their action.
2.2. Modifications that prevent the arrival of the antibiotic to the target organ
Porins, for example, are cell proteins that allow the entry and exit of compounds from the cell. In a normal situation, the antibiotic would enter the bacteria carrying out its known activities, but what happens if, due to a mutation, the porins are modified and do not allow their entry? Effectively, the antibiotic loses all usefulness.
We go further, because there are bacteria that present mechanisms of active expulsion of the antibiotic despite the fact that it manages to enter the cell. Thus, they prevent lethal concentrations of it from occurring.
23. Target Organ Alteration
Another of the mechanisms that antibiotic-resistant bacteria can carry out is the modification of the target organ itself attacked by the antibiotic. For example, penicillin binds to specific proteins (PBPs). If these are modified, the affinity of the drug decreases, preventing its operation.
2.4. Alternative routes
A final viable strategy is to look for alternative routes to obtain compounds that cannot be synthesized by the action of the antibiotic. For example, if the antibiotic inhibits the synthesis of folic acid (an essential vitamin), some bacteria can capture it directly from the environment and are thus able to develop normally.
clinical importance
We are not moving solely within a theoretical framework of biochemical interest, since all these mechanisms are expressed in the population in various ways.
For example, a study in Thailand showed that the use of Trimethoprim-sulfamethoxazole, antibiotics used for years to treat non-cholera diarrhoea, had completely lost their effectiveness. This has also been recorded at a temporal level and not only geographically, because after six years of the introduction of aminoglycosides in the health field (previously very effective bactericides), resistant strains of Staphylococcus began to be observed.
The world health organization throws up figures of disastrous prognosis:
- In the United States, it is estimated that more than 63,000 people die annually from hospital-associated (usually resistant) bacterial infections.
- In Europe, there are more than 25,000 deaths annually from multi-drug resistant (MDR) bacterial infections.
- The incidence of diseases such as pneumonia, tuberculosis or salmonella, and more complex treatments, is increasing.
What to do about this situation?
In general, the best prevention is to limit the use of antibiotics . If we do not overexpose bacteria to antibiotics, it will be less easy for the most resistant to be selected over time. Special emphasis is also placed on following the treatments to the letter, because if the drug is stopped before prescribed, it can promote that the most resistant bacteria endure the treatment.
A study in the United Kingdom yielded worrying data regarding this issue, since in a relatively large sample group, it was detected that 11.3% of patients with prescribed antibiotics left them early. The reason? That 65% of them said they already felt good.
Conclusions
The appearance of bacteria resistant to antibiotics is something relatively inevitable, since, as we have seen, it responds to a mechanism of natural selection that has been present since the origin of life. Living beings are changeable, as they mutate continuously. Sometimes these changes are deleterious and other times they grant resistances, as is the case described here.
The most immediate and concrete solution is to make the population aware of the responsible use of antibiotics. That is, never consume them without prior prescription and always follow the exact durations indicated . Even so, this problem is one that as a society we will always have to live with. We can only hope for one thing, and that is that science advances by creating new drugs faster than the bacterial mutations themselves.
Bibliographic references
- Stewart, P. S., & Costerton, J. W. (2001). Antibiotic resistance of bacteria in biofilms. The lancet, 358(9276), 135-138.
- Zaman, S. B., Hussain, M. A., Nye, R., Mehta, V., Mamun, K. T., & Hossain, N. (2017). A review on antibiotic resistance: alarm bells are ringing. Cureus, 9(6).
- World Health Organization (WHO). Antibiotic resistance. Collected on July 18 at https://www.who.int/es/news-room/fact-sheets/detail/resistance-a-los-antibi%C3%B3ticos
- RM, DP (1998). Bacterial resistance to antimicrobials: its importance in decision-making in daily practice. Inf Ter Sist Nac Salud, 22, 57-67.
To the classic question “what do you do?” I always answer “basically I am a psychologist”. In fact, my academic training has revolved around the psychology of development, education and community, a field of study influenced my volunteer activities, as well as my first work experiences in personal services.