Definition of Microbial Resistance

Rodrigo Arredondo Fernandez
Lic. in biology

Microbial resistance is the ability of microorganisms to resist the effect of antimicrobial drugs to which, under normal conditions, they would be susceptible.

There are many factors by which a group of microorganisms develops this capacity. Antibiotics or antimicrobial agents are produced by other microorganisms, however, there are genes that give resistance to these products that are present in most of the microorganisms that produce. These genes can be passed between species, so resistance is a widespread feature. There are mechanisms described that exemplify this capacity, depending on the type of antibiotic in question.

First, there is reduced permeability, a feature that prevents the drug from being taken up by the cell, especially effective against the penicillin family.

Secondly, there is the inactivation of the antibiotic, that is, by modifying enzymes such as methylases, acetylases and phosphorylases, which alter the drug molecule so that it becomes dysfunctional, especially against penicillins, chloramphenicol and aminoglycosides.

Thirdly, there is the alteration of the target, that is, they change the structure or composition of the molecule to which the drug is attached. designed to attack, so that the antibiotic "not finding" the vulnerable point of the microorganism, is disabled to fight it. A fourth mechanism is the development of metabolic pathways that resist the effect of the drug, something that has been seen in enteric bacteria. Finally, bacteria of the genus Staphylococcus, Bacillus, among others, have developed complex systems of recognition of this type of substances that are capable of eliminating it from their interior through bombs of expulsion.

Why does microbial resistance to antibiotics develop?

As mentioned, these mechanisms are encoded in resistance genes within your chromosome or Mobile, transferable chromosomes called R plasmids (of endurance). The constant use of antibiotics in medicine, veterinary medicine and agriculture encourages these resistance genes to undergo a process of selection and are transferred between microorganisms, leaving those microorganisms most apt to survive even the most aggressive drugs. By discovering or synthesizing new antibiotics, new strains capable of resisting them appear, something similar to an arms war against microorganisms.

That is why self-medication with antibiotics, the excessive use that is given to them as a supplement in animal feed and as additives prophylactics, even not finishing a prescribed treatment with these drugs, accelerates the appearance of resistant strains, now called superbugs.

What is the medical importance?

The impact that the development of microbial resistance has on public health is serious, as it becomes more frequent than the antibiotic compound designated for the treatment of a particular infection may need to be changed to another when the disease-causing microorganism in question becomes resistant.

An example of this is the development of resistance of Neisseria gonorrhoeae, the bacterium that causes gonorrhea, to penicillin and other drugs. Penicillin was widely used to treat this disease until the 1980s, when it had to be replaced by ciprofloxacin, however, this was only efficient for a while and only in some communities. The next treatment was based on ceftriaxone, a type of penicillin capable of resisting alteration by the penicillinase enzyme.

That is why the treatments against this type of infection have to be updated every year to deal with the continuous appearance of strains resistant to antibiotics. To do this, it is sought that in the design of new drugs they are analogous to the existing ones, that is, that they have the same purpose but that the molecular structure is different so that the defenses of microorganisms in question. Another alternative is to find new weak points for pathogens, which are generally found in important metabolic pathways for their development.

The guidelines for action in this regard that have been established by the centers for disease control and prevention is the prevention of infections, rapid and effective diagnoses, prudent use of antimicrobial agents and breaking the chain of pathogens.