Nature and Key Characteristics
Essentially, antibiotics are chemical compounds classified as chemotherapeutic agents. By origin, they are divided into three major groups: biological (fully natural), semisynthetic (derivatives of natural substances), and synthetic analogs of natural compounds.
A key feature of these substances is their efficacy even at very low concentrations. Furthermore, they exhibit strict action selectivity. This means the drug can target and damage or completely destroy bacteria and tumor cells while exerting minimal impact on the tissues of the host organism (human or animal).
Natural Sources (Producers)
The biological purpose of antibiotic production lies in natural antagonism. In nature (e.g., in soil), microorganisms secrete these substances as a powerful tool for survival and competition with other bacterial species for nutrient resources.
Animal cells and plants are also capable of secreting antimicrobial components (such as phytoncides), but they have not found widespread application as industrial producers for medicine. Microbes hold absolute leadership in production:
- Actinomycetes (Actinomycetes). These branching bacteria play a crucial role, with the genus Streptomyces being the primary source of approximately 80% of all known natural antibiotics.
- Molds (Fungi). The main producers here are the genera Cephalosporium and Penicillium. They synthesize natural $\beta$-lactams as well as fusidic acid.
- Typical bacteria. These include eubacteria, bacilli, and pseudomonads. They specialize in producing polypeptide antibiotics such as bacitracin and polymyxins.
Industrial Production Methods
Modern pharmacology uses three main technological approaches to produce antibacterial drugs:
- Biological synthesis (fermentation). Used to obtain exclusively natural antibiotics. Producer microbes are cultivated under strictly specified optimal conditions. During their life cycle, they secrete the target substance, which is then collected and thoroughly purified.
- Biological synthesis with chemical modification. This combined pathway is used to create semisynthetic antibiotics. At the first stage, the natural base is obtained via biosynthesis. At the second stage, the molecular structure is chemically modified (e.g., by attaching new radicals). This aims to improve pharmacological characteristics and enhance the antimicrobial properties of the original drug.
- Chemical synthesis. Used to create synthetic analogs. The structure of a natural antibiotic is fully recreated by chemical methods in the laboratory, without the participation of living microorganisms. A classic example of this approach is chloramphenicol, which is structurally identical to the natural substance but synthesized artificially.
General Classification by Chemical Structure
Depending on the chemical structure of the molecule, all antibiotics are divided into major families and classes. The main list includes:
- Beta-lactams (this extensive group includes penicillins, cephalosporins, carbapenems, and monobactams)
- Macrolides (and azalides)
- Tetracyclines
- Aminoglycosides
- Glycopeptides
- Lincosamides
- Polypeptides
- Polyenes
- Rifamycins
- Chloramphenicol
- Miscellaneous groups (including fusidic acid, fusafungine, and other agents not included in major classes)