Our modern life is impossible to imagine without antibiotics. Today they are used everywhere: in agriculture, household chemicals, food industry, medicine (amoxil), etc. Undoubtedly, their use has greatly facilitated the life of a person, but is it safe to use them without control?
History of the discovery of antibiotics.
In 1928, the English physician Alexander Fleming made a discovery that marked the beginning of a new era in medical science. He drew attention to the fact that many microbiologists had observed before him, but they did not attach importance to the discovered phenomenon. On a dense nutrient medium in a Petri dish, the researcher grew colonies of bacteria. During the experiment, a mushroom spore accidentally dropped from the air started the growth of a fungal colony among bacteria. But the most important thing was that around the fungal microorganisms, the bacteria suddenly stopped multiplying. Fleming suggested that the fungus colony releases a substance into the nutrient medium that prevents the growth of bacteria. His guess was completely confirmed. Later, the staff of the University of Oxford, the Briton Howard Florey and a native of Germany, Ernst Cheyne, managed to isolate and determine the structure of the world’s first antibacterial substance, called penicillin after the mushroom-producer belonging to the genus penicillin. So humanity has acquired a tool to fight many deadly bacterial infections. Fleming, Flory, and Cheyne won the Nobel Prize for their discovery in 1945. Penicillin was followed by the discovery of other antibacterial substances.
The term “antibiotic” (translated from Greek – “against life”) was proposed in 1942 by an American microbiologist, a native of Russia, a specialist in soil microbiology Zelman Waxman. His name is also associated with the discovery of another well-known antibacterial substance-streptomycin, which is still used to treat tuberculosis. Both penicillin and streptomycin are produced by soil microorganisms. But there are other organisms that produce antibacterial substances. Currently, about 30,000 antibiotics of natural origin are known, synthesized by living creatures of various taxonomic groups.
According to the most common definition in the scientific community, antibiotics are substances produced by various living organisms that can destroy bacteria, fungi, viruses, ordinary and tumor cells or inhibit their growth. But this does not mean that all existing antibiotics are produced by living cells. Chemists have long learned to improve and enhance the antibacterial properties of natural substances by modifying them using chemical methods. The compounds obtained in this way belong to semi-synthetic antibiotics. Of the huge number of natural and semi-synthetic antibiotics, only about a hundred are used for medical purposes.
Classification of antibiotics – effect of antibiotics
A huge variety of antibiotics and their effects on the human body was the reason for the classification and division of antibiotics into groups.
According to the nature of the effect on the bacterial cell, antibiotics can be divided into three groups
- Bacteriostatic (bacteria are alive but unable to reproduce)
- Bactericides (bacteria are killed, but physically continue to be present in the environment)
- Bacteriolytic (bacteria are killed and bacterial cell walls are destroyed)
Classification by chemical structure, which is widely used in the medical environment, consists of the following groups:
- Macrolides are antibiotics with a complex cyclic structure. Action-bacteriostatic.
- Tetracyclines-used for the treatment of respiratory and urinary tract infections, treatment of severe infections such as anthrax, tularemia, brucellosis. Action-bacteriostatic.
- Aminoglycosides-have high toxicity. They are used to treat severe infections such as blood poisoning or peritonitis.
- Levomycetins-Use is limited due to the increased risk of serious complications – bone marrow damage, producing blood cells. Action – the bactericidal.
- Antifungal-destroy the membrane of fungal cells and cause their death. Action-bacteriolytic. Gradually replaced by highly effective synthetic antifungal drugs.
Effect of antibiotics: Application in medicine
Antibiotics are very widely used in medical practice for the treatment of various bacterial, fungal infections and some tumors.
Antibiotics are used to prevent and treat inflammatory processes caused by bacterial microflora.
Over the past 35 years, thousands of antibiotics with different spectrum of action have been discovered, but a limited number of drugs are used in the clinic. This is mainly due to the fact that most antibiotics do not meet the requirements of practical medicine.
According to the spectrum of antimicrobial action, there are antibiotics active against gram-positive microorganisms (penicillins, macrolides, etc.), active against gram-negative and gram-positive microorganisms (aminoglacosides), broad-spectrum antibiotics (levomycetin, tetracycline), antibiotics with antifungal action (mainly polyenes).
Great advances in the development of chemistry in recent years have led to the creation of antibiotics with directionally modified properties, with prolonged action, active against penicillin-resistant staphylococci or with a wide spectrum of action.
Due to the widespread use of antibiotics, resistant forms of microorganisms, especially staphylococci, have appeared. New semi-synthetic penicillins active against resistant staphylococci, as well as some gram-negative microbes, are of great practical importance in the fight against this phenomenon.
Semi-synthetic penicillins-methicillin, oxacillin, cloxacillin, dicloxacillin-are not destroyed by penicillinase secreted by resistant staphylococci, and are highly active against staphylococci resistant to penicillin. Drugs of this group are effective in postoperative wound infections, empyema, sepsis, osteomyelitis, carrier of pathogenic staphylococci.
Semisynthetic penicillin of a wide spectrum of action – ampicillin-is of great interest, since it acts not only on gram-positive, but also gram-negative microbes (pathogens of typhoid fever, paratyphoid, dysentery). Ampicillin is used for upper respiratory tract infections, diseases of the urinary tract caused by E. coli, proteus, fecal streptococcus. In some cases, ampicillin is effective in the rehabilitation of carriers of typhoid bacillus. Semi-synthetic penicillins active against Pseudomonas aeruginosa were obtained.
Semi-synthetic preparations are also prepared on the basis of 7-aminocephalosporanic acid. Derivatives such as cephalothin, cephaloridine, find practical application in sepsis, pneumonia and other infections. These drugs usually do not cause allergic reactions in people who are sensitive to penicillin.
Of the broad-spectrum antibiotics, the tetracycline group occupies an important place. Currently, there are many tetracycline preparations for various routes of administration (topically, orally, parenterally). Semisynthetic tetracyclines-metacycline and doxycycline, characterized by prolonged action, deserve attention.
Broad-spectrum antibiotics are successfully used in a number of diseases of the gastrointestinal tract and genitourinary tract. However, there is still an urgent problem of finding new effective drugs for the treatment of intestinal infections. There is a progressive increase in the resistance of dysentery microbes to the antibiotics used. Currently, the most reasonably and effectively combined the use of antibiotics (polymyxin, tetracycline, aminoglycosides) with sulfonamides of prolonged action.
Among the acute intestinal diseases in children of early age has a significant place coelenterate caused by enteropathogenic Escherichia coli. This microorganism is sensitive to aminoglycosides and polymyxin. In case of brucellosis infection, intramuscular administration of tetracycline with vaccine and hormones is effective in the experiment and clinic.
Most antibiotics that have an antifungal effect are derived from actinomycetes. These are primarily polyene antibiotics, which, depending on the number of double bonds, are divided into tetraenes, pentaenes, hexaenes, heptaenes, The most practical value has been acquired by heptaenes, which include trichomycin, candicidin, amphotericin B, and from tetraenes – nystatin. All polyene antibiotics have similar chemical structure and properties, and are effective in fungal diseases.
In recent years, a number of antibiotics with antitumor effect have been significantly expanded. Most of them inhibit the synthesis of nucleic acids of the cancer cell.
Antiviral antibiotics that would be used in the clinic do not yet exist. As an active antiviral agent, interferon is used, which is recommended for the prevention and early treatment of influenza. In addition to exogenous interferon, various inducers of its formation in the body are used – non-pathogenic viruses, polysaccharides (prodigiosan), nucleic acids, etc.
The widespread use of antibiotics over a 30-year period made it possible to identify the diversity of their side effects and develop measures to combat it. The widespread use of antibiotics has naturally led to the spread of bacteria resistant to them. The ability to form resistant strains in different microbes varies. Stable forms of staphylococci, Escherichia coli, Enterococcus, and mycobacteria appear most quickly.
To combat resistant forms of microorganisms, in addition to creating new drugs with a different mechanism of action, combination therapy is widely used.
One of the conditions for preventing the development of resistant forms of microorganisms is the periodic replacement of widely used antibiotics with new, recently created or rarely used ones. Such drugs are called “reserve antibiotics”.
An important task is to create new antibiotic preparations with a pronounced etiotropic effect, which would be active against resistant forms of microbes and would have a minimal side effect on the human body.
The success of antibiotic therapy largely depends on the combination of antibiotics with substances that stimulate the defense forces of the macroorganism (prodigiozan, lysozyme, protamine, etc.).
The use of antibiotics in the food industry.
During the storage of food products, their spoilage occurs, caused by the development of microorganisms. To combat harmful microflora, along with physical methods, chemical methods are also used, including the use of antibiotics.
The use of antibiotics, which have a powerful antibacterial effect and relatively low toxicity to the human body, allows you to preserve food products without losing their nutritional value. Antibiotics with a broad spectrum of action are most effective for this purpose. When testing their effect on various microorganisms isolated from spoiled meat, antibiotics suppressed the development of 70 – 80% of the strains.
Antibiotics are used for preserving meat, fish, poultry, milk, fruits, vegetables, etc. Preservation of fresh meat, fish and poultry is difficult due to the fact that these products are an ideal environment for the development of microorganisms.
The antibiotic is fed to animals immediately before slaughter or injected under pressure into the carotid artery immediately after slaughter. This allows you to increase the shelf life of fresh meat to 2-3 days and improve its appearance, smell, color. Spraying butchered and chilled beef carcasses with an antibiotic solution is also effective. The addition of an antibiotic extends the shelf life of minced meat.
The use of antibiotics can significantly extend the shelf life of fresh fish. The fish is immersed in an antibiotic solution for 1-5 minutes. The shelf life of fish is also increased when it is kept on crushed ice containing 1-2 mg/l of chlortetracycline.
Similar methods are used to extend the shelf life of poultry. In some cases, the shelf life can be increased by 2-3 times.
The use of antibiotics in the storage and transportation of milk without cooling allows you to extend the shelf life to four days at 30 °C. A mixture of patulin with chlortetracycline protects milk from spoilage for 10 days. With further use of milk, it is necessary to inactivate the added antibiotic: penicillin-with the addition of penicillinase, chlortetracycline -with three-substituted sodium phosphate; milk is kept for several hours at 20 °C.
In the production and storage of cheeses, an antibiotic is used that suppresses the development of clostridial and other forms of bacteria involved in the process of spoiling cheeses.
It is possible to use antibiotics in the manufacture of canned vegetables, in this case, antibiotics obtained from higher plants (phytoncides) are often used.
In all cases of use of antibiotics for food preservation, it is necessary to take into account the possibility of their ingestion in small quantities in the human body. It is shown that 200 g of canned meat (with the use of an antibiotic) contains approximately 1/1000 of the daily therapeutic dose of the drug. Although such subthreshold doses do not exhibit pharmacological effects, they can affect the sensitivity of macroorganisms. Therefore, it is necessary to pay special attention to the removal of antibiotics before the final preparation of food products. In addition, in the food industry, it is desirable to use antibiotics that are not used for medicinal purposes.
Effect of antibiotics conclusions:
Based on the conducted research, the following conclusions can be drawn:
- Antibiotics are widely used in medicine, veterinary medicine, agriculture and food processing.
- In a certain concentration, antibiotics can increase seed germination, accelerate plant development, and stimulate root formation.
- On adult plants, penicillin acts depressingly, causing thinning of the leaves, shrinking of their edges, stretching of the internodes of the stem.
- A high concentration of the antibiotic leads to the death of protozoa.
- The antibiotic penicillin prevents the growth of white mold, but promotes the growth of yellow mold.
- When treating with antibiotics, you need to follow the rules for taking medications.