Antibiotic-resistant bacteria represent a serious public health problem because treatment against them has become limited. This problem is not new, since, as we will see below, resistance has accompanied the use of antibiotics throughout their history. However, resistance was reported so quickly that it is worth asking - which came first: the antibiotics or the resistant bacteria? - To answer this question, we will talk about antibiotics and bacterial resistance to antibiotics.

A look at the history of antibiotics

Although we have all used antibiotics on more than one occasion, few of us know precisely what they are. For this case, we will define antibiotics as drugs used to treat infections caused by bacteria with the ability to kill or stop their production.

Because bacterial infections have accompanied mankind since its origins, some heavy metals have been used effectively to combat them, for example, salvarsan, a derivative of arsenic (see Saber Más No. 29:24), which was used successfully against syphilis (sexually transmitted bacterial infection) until the introduction of the first antibiotic in 1940.

But wait a minute, if there were already effective compounds against bacterial infections, why is the discovery of antibiotics so important? The answer is simple: heavy metal derivatives can poison cells, but they do not distinguish a bacterial cell from a human cell. Therefore, the discovery of agents that kill only bacteria ushered in a new era.

The first antibiotic was discovered by Alexander Fleming in 1928 and was given the name penicillin because it was isolated from the fungus Penicillium notatum. Largely due to the wounded during World War II, by 1940 this agent was already a commonly used drug. Unfortunately, two years later the first reports of bacteria resistant to the effects of the antibiotic appeared.

In 1942, in Selman Waksman's laboratory, streptomycin was discovered, an antibiotic used to treat tuberculosis (a highly contagious pulmonary infection). Although its use has become almost obsolete due to cases of resistance, its importance lies in the fact that it was the first antibiotic isolated from a bacterium of the genus Streptomyces. Currently, more than half of the antibiotics we use have been identified in bacteria of this genus.

One of the most outstanding advances in antibacterial treatment occurred in 1962, with the introduction of quinolones, a group of synthetic antibiotics. Because of their origin, it was believed that bacterial resistance would not be an immediate problem, but as had happened before, the bacteria were primed and cases of resistance were immediately reported.

The search for more potent antibiotics continues, however, each new finding is accompanied by the emergence of resistance. Although there are currently more than ten groups of antibiotics, bacterial resistance is always present.

How is bacterial resistance generated?

A resistant bacterium can withstand the lethal effects of antibiotics and in general, there are three ways to defend itself: 1) Mutating, the bacterium changes some characteristic so that the antibiotic does not recognize it easily; 2) Expelling the antibiotic, many compounds need to remain inside the bacteria to carry out their function if it is rejected it cannot act; 3) Modifying the antibiotic, the most effective and definitive way to deactivate an antibiotic is to change its chemical structure.

Each of the above three options presents multiple challenges. The most common defense is to accumulate mutations, however, many changes can cause the bacteria to lose viability. The expulsion systems are not very efficient, as they are not designed to expel antibiotics. Finally, to deactivate an antibiotic, it is necessary to have evolved along with it, because very specific enzymes and biological catalysts that arose and/or adapted at the origins of bacterial life are needed. Therefore, it was believed that antibiotic-producing microorganisms (fungi and bacteria) would be the only ones with the ability to modify antibiotics.

The means to resist are not easily acquired, and an antibiotic used in the right way would kill all bacteria without giving them time to fight back.

So why is bacterial resistance a problem? - How many times have we not stopped treatment because we are supposedly "feeling well"? Or perhaps more seriously, we take them when they are not needed. These circumstances contribute to the selection and distribution of resistant bacteria.

Another resistance factor is that most antibiotics originate from microorganisms that have lived with the bacteria we are now trying to eliminate for their entire existence. So many bacteria already had resistance systems in place before we confronted them with our commercial antibiotics.

So, which came first?

We can affirm that antibiotic resistance is mainly due to two causes. The first is the misuse and abuse of antibiotics and the second is the extraordinary ability of bacteria to adapt to adverse conditions.

Both antibiotics and resistant bacteria have coexisted in nature and one could not exist without the other. However, we broke the balance by extending the use of these agents, now resistant bacteria seem to be everywhere and that is because antibiotics are also everywhere.

By Víctor M. Chávez-Jacobo, Source: Saber Más. Journal for the dissemination of the Michoacán University of San Nicolás de Hidalgo No. 32