In this day and age where comic book characters or action movie heroes depict men and even beings from other planets with amazing powers or abilities and are therefore described as "superheroes", it is not surprising to hear the word "superbugs".
This term is used to refer to bacteria resistant to various types of antibiotics, drugs that are used to combat the diseases they cause. However, unlike superheroes who are fictional characters, superbugs are so real that they are becoming increasingly common.
For many years, antibiotics have been used to treat diseases caused by these microorganisms. But, in recent decades, some of them have been identified as superbugs because they are difficult to combat with current medicines, mainly because antibiotics have lost their effectiveness against them.
Superbugs and our health
Superbugs represent a worldwide health problem, so much so that the World Health Organization (WHO) has reported up to 3.5% of bacteria related to tuberculosis that cannot be fought with currently available antibiotics. On the other hand, according to the U.S. Centers for Disease Control and Prevention, it is estimated that drug-resistant bacteria infect more than two million people and kill at least 23,000 each year in the U.S. alone. Shockingly and alarmingly, the WHO estimates that by 2050, antibiotic resistance will be the leading cause of death in the world.
How do superbugs emerge?
Antibiotic resistance is almost as old as antibiotics themselves, and basically, any bacterium can become resistant to one or more antibiotics. Antibiotic resistance occurs when bacteria stop responding to drugs, making it more difficult to treat infections, increasing the risk of disease spread and the appearance of severe forms of the disease, and even death.
When we talk about superheroes, in most cases the origin of their "powers" is due to mutations (changes in their genetic material), or to the fact that these characters have been given an object (ring, stone, etc.) that transforms them. Something similar happens in bacteria and it is extremely interesting to observe that, through mechanisms similar to those of superheroes, organisms as small as bacteria acquire abilities that allow them to be resistant.
Mutations in genetic material
One of the most common mechanisms for the acquisition of bacterial resistance to antibiotics is through mutations in the DNA (genetic material) of a sensitive bacterium. Several antibiotics act by binding to molecules in the bacterial cell (called target molecules), affecting their normal functions and leading to growth arrest or death of the bacterium. Thus, changes in the chemical structure of the target molecules (generated by mutations) can prevent the recognition and binding of the antibiotic, allowing the bacterium to continue its normal functioning.
On the other hand, in general, some bacteria are less permeable than others to antibiotics because they have an outer membrane (called Gram-negative bacteria) that forms an impermeable barrier to many chemical compounds, including antibiotics. However, several antibiotics can cross these membranes through membrane proteins called porins that allow an increase in the concentration of the antibiotic inside the bacteria and, therefore, greater cell damage.
The transport of antibiotics into bacteria can be affected by mutations in the DNA of a bacterium, resulting in a decrease in the expression of genes encoding porins, which leads to a decrease in the number of these proteins synthesized, thus decreasing the permeability of the outer membrane and the entry of antibiotics into the cell, which manifests itself as an increase in antibiotic resistance.
This implies that during a bacterial infection a phenomenon called selection can occur, wherefrom a population of bacteria some with a mutation that confers resistance arise and, therefore, despite antibiotic treatment, they can grow and proliferate. This is where superbugs appear.
Acquisition of genetic material to resist antibiotics
Antibiotic-sensitive bacteria can also become resistant when they acquire DNA by transferring genetic material from a resistant bacterium. In this way, bacteria can acquire antibiotic resistance mechanisms and, in turn, actively participate in the spread of resistance among bacteria. Antibiotic resistance systems acquired by gene transfer are varied and include both antibiotic expulsion and antibiotic modification or degradation.
A large number of bacteria possess systems that carry out active expulsion of compounds that are toxic to them, including certain antibiotics. Although highly specific expulsion systems have been described that only expel one type of antibiotic. These systems generate a decrease in the concentration of antibiotics inside the cell, which prevents the generation of harmful effects or the death of the bacteria.
On the other hand, the modification of the chemical structure of antibiotics by bacterial enzymes can cause their inactivation, since the changes generated to interfere with the recognition and/or binding with the target molecules, and can even lead to the antibiotic being degraded by the bacterial cell.
Where are superbugs found?
Antibiotic-resistant bacteria can be present in each of us, in animals, food, plants, and the environment. When antibiotics are used correctly, they can help destroy disease-causing bacteria.
But if it has been misused, for example, self-medication or not taking the full treatment, the consequence is serious because it is achieved not only the death of a large number of sensitive bacteria but also the death of some beneficial bacteria, such as those essential in the digestion of food. As well as a significant impact on the selection of resistant bacteria or superbacteria, which thrive in the face of this attack and spread, even transferring their resistance genes to other bacteria.
While superbugs represent a global health problem, in recent years a global alliance for antibiotic research and development, a joint initiative with the WHO, has been formed to develop and distribute new treatments against currently identified resistant bacteria, especially those that pose the greatest threat to human health.
COVID-19 and superbugs
Although it is still too early to assess its full impact, today, the COVID-19 pandemic has revolutionized the entire world in many areas, ranging from social, economic, and educational, to psychological and public health, as it brought with it new challenges in bacterial resistance.
Studies conducted in different hospital centers revealed the elevation in the rate of antibiotic prescription in patients with COVID-19 as, although antibiotics do not treat viruses such as SARS-CoV-2 (causing COVID-19 disease), patients with COVID-19 or any type of influenza virus become susceptible to contracting a secondary bacterial infection, leading to antibiotic use.
It has been suggested that a potential consequence of the COVID-19 pandemic, is the long-term spread of antimicrobial resistance in the acute care setting as a result of increased patient exposure to antibiotics, often used suboptimally or inappropriately, which could lead to an increase in the emergence of superbugs.
However, in the scenario described concerning superbugs, there is the potential to help ensure that currently used antibiotics remain effective by using them correctly and taking them only when prescribed and necessary.
Written by Bianca Yareli Román Cárdenas and Martha Isela Ramírez Díaz, Source: Saber Más Magazine publishes popular science articles in a digital (web) format.