Antibiotics are substances that selectively suppress the vital activity of microorganisms. “Selective influence” refers to the activity exclusively in the relationship of microorganisms while preserving the viability of host cells and the impact not on all, but only on certain genera and types of microorganisms. For example, fusidic acid has a high activity against staphylococci, including methicillin-resistant, but does not act on pneumococci of BSA. The idea of the broad spectrum of activity of antibacterial drugs is closely related to selectivity.
However, from today’s point of view, the division of antibiotics into broad-spectrum and narrow-spectrum drugs seems conditional and is subject to serious criticism, mostly due to the lack of criteria for such a division. It is wrong to assume that broad-spectrum drugs are more reliable, effective, and stronger, and that the use of narrow-spectrum antibiotics contributes less to the development of resistance, and so on. This does not take into account acquired resistance, as a result, for example, tetracyclines, which in the first years of use were active against most clinically significant microorganisms, have now lost a significant part of their spectrum of activity, in fact, due to the formation of acquired resistance in pneumococci, staphylococci, gonococci, enterobacteria.
Cephalosporins of the third generation are usually considered as drugs with a wide range of activity, despite the fact that they do not act on MRSA, many anaerobes, enterococci, Listeria, atypical pathogens, etc. It is most rational to consider antibiotics from the point of view of clinical effectiveness in infection of a certain organ localization, since the clinical evidence of effectiveness obtained in well-observed (comparative, randomized, prospective) clinical experiments is undoubtedly more significant than a conventional label such as “broad (or narrow) spectrum antibiotic activity”. Traditionally, antibacterial drugs are divided into natural (proper antibiotics, such as penicillin), semi-synthetic (products of modification of natural molecules, such as amoxicillin or cefazoline) and synthetic (such as sulfonamides, nitrofurans). Currently, this division is no longer relevant, since a number of natural antibiotics are obtained by synthesis (chloramphenicol), and some drugs (fluoroquinolones), called “antibiotics”, are synthetic compounds.
Antibiotics should be distinguished from antiseptics that act indiscriminately on microorganisms and are used for their destruction in living tissues, and disinfectants intended for the indiscriminate destruction of microorganisms outside of a living organism (for disinfection of care items, surfaces, etc.). Antibiotics are the most numerous group of medicines. For example, in Russia, currently 30 different groups of antibiotics are used, and the number of drugs is approaching 200. All antibiotics, despite the differences in chemical structure and mechanisms of action, have a number of unique features. First, the uniqueness of antibiotics is that, unlike most other drugs, their target receptor is not in the tissues of the human body, but in the cell of a microorganism.
Secondly, the dynamism of antibiotics is not long-term, but decreases over time, due to the development of drug resistance. Antibiotic resistance is an indispensable biological phenomenon, and it is almost impossible to prevent it. Third, antibiotic-resistant microorganisms pose a threat not only to the patient from whom they were isolated, but also to many other people, even separated by time and space. As a result, the fight against antibiotic resistance has now become global. The division of antibiotics, as well as other drugs, into groups and classes is well known. Such a division is of great importance in terms of understanding the spectrum of activity, pharmacokinetic characteristics, the nature of adverse drug reactions, and so on. However, it is a mistake to consider all drugs in the same group (class, generation) as interchangeable.
There may be significant differences between drugs of the same generation that differ only by one molecule. For example, among the cephalosporins III generation of clinically significant activity against Pseudomonas aeruginosa have only ceftazidime and cefoperazone. As a result, even if you acquire data on the sensitivity of Pseudomonas aeruginosa to Cefotaxime or Ceftriaxone, these drugs should not be used to treat this infection, since the results of clinical trials confirm a high frequency of inefficiency. The second example is the difference in the pharmacokinetics of antibacterial drugs: cephalosporins of the first generation (Cefazolin) are not allowed to be used in the treatment of bacterial meningitis due to poor permeability through the BBB.
The isolation of bactericidal and bacteriostatic antibiotics is of primary practical importance in the treatment of severe infections, especially in patients with immune disorders, when it is necessary to prescribe bactericidal drugs. Of the pharmacokinetic characteristics, the most significant when choosing a drug are periods of partial elimination and bioavailability (which is typical for drugs of internal use). Therefore, despite the many common features that combine antibacterial drugs, when prescribing them, it is necessary to take into account the properties of each drug and the consequences of their clinical use, identified in well-verifiable clinical trials.
The discovery of penicillin extended a person’s life by an average of 30-35 years. Scientists in their research have shown how antibiotics fight disease-causing bacteria.