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Antibiotics: history, classification and types

 Antibiotics are medicines used to eliminate bacteria and treat the effects of bacterial infection, and they are not effective against viruses or any other non-bacterial infection, and there are many types, each type has a specific spectrum, so you must follow the instructions of the treating physician to choose the appropriate antibiotic for each case.

antibiotics detailed classification


A brief history of the discovery of antibiotics

Although about two centuries ago, doctors did not know the types of bacteria that cause infection, the history of using antibiotics as a treatment for infection is too old, contrary to what people think.


Many extracts of molds and some algae were used in ancient civilizations to treat infections. For example, the American Infectious Diseases Association says that the ancient Egyptians used mouldy bread to treat infected wounds, and they succeeded in doing so [source].


Until the late 19th century, the first cause of death around the world was bacterial infection, especially pneumonia and bacterial gastroenteritis, until the time of the discovery and manufacture of many antibiotics.


In 1909, the German physician "Paul Ehrlich" noticed that some chemical dyes colored some bacterial cells but not others, and he concluded that chemicals are capable of killing bacteria inside the body can be manufactured in large masses, and indeed after several researches, "Ehrlich" was able to discover  a substance called "arsphenamine" that was effective in treating syphilis, and this was the first modern antibiotic in history, but he called it "chemotherapy".


The term "antibiotic" was first used in the 1940s by the Ukrainian-American scientist "Salman Waksman", who alone discovered more than 20 antibiotics during his life.


Penicillin - the most famous antibiotic currently - was discovered by "Alexander Fleming" by chance, as he had gone on vacation and forgot a dish with the culture of Staphylococcus aureus bacteria in his laboratory and left it without a cover, so the fungus (Penicillium notatum) grew on it, and Fleming noticed the death of All the bacteria found in the place where the fungus grew, he repeated the experiment and confirmed the super ability of this fungus, even at very small concentrations, to kill bacteria, even after diluting the concentration of the fungus 800 times, it was able to eliminate the bacteria.

Alexander Fleming


After conducting many experiments in laboratories of British pharmaceutical companies, the ability to produce penicillin as an antibiotic in large quantities for the public was confirmed, and it was then widely used in treating World War II wounded soldiers in hospitals and on battlefields, and achieved amazing success, so that by the end of World War II it was called penicillin The title of "miracle medicine", and later became available commercially.


Classification of types of antibiotics

Medically, antibiotics are divided into groups or families, each group containing many antibiotics that are similar in the way they work, the type of bacteria that are effective against them, and the possible side effects.


These groups are classified as follows:

  • Penicillins such as aqueous penicillin and amoxicillin and their derivatives such as Augmentin, Megamox.
  • Cephalosporins, most of which are injections such as Triaxone, Cefotaxime, Cefaxone, Cefopid, and others.
  • Aminoglycosides such as amikacin, gentamicin, streptomycin and neomycin
  • Carbapenems such as imipenem and meropenem
  • Quinolones and Fluoroquinolones, the most famous of which are Tavanic, Cipro, Tavasin and Leviflox.
  • Glycopeptides and lipoglycopeptides, the most famous of which is Vancomycin.
  • Macrolides such as azithromycin, clarithromycin and zithron, commonly used to treat corona, as well as zithrokan.
  • Monobactams, the most famous of which is Aztreonam.
  • Oxazolidinones, the most important of which are linezolid and tidazole
  • Polypeptides are used more in the treatment of external wounds, the most famous of which are "Bacitracin" spray, Colistin and Polymyxin B.
  • Rifamycins, the most important drug of all, is rifampicin, which is used to treat tuberculosis.
  • Sulfa (Sulfonamides), the most famous of which is "Septrin", which contains a mixture of sulfamethoxazole and trimizoprim
  • Tetracyclines are well known in the treatment of dental caries and gums, the most famous of which is Doxy-cycline. The most important trade names in this group are Doxycost and Doxymycin.
  • Streptogramins
It should be noted that Carbapenems, Cephalosporins, and Monobactams, in addition to penicillins, are grouped in one family called "beta-lactams" because they all share a "beta-lactam" ring in their chemical structure.

It is also worth noting that there are some other antibiotics outside the previous classification and they are classified individually because they do not belong to any of the previous groups, these antibiotics are:

  • Chloramphenicol, used in the treatment of tuberculosis and some other diseases
  • clindamycin
  • daptomycin
  • Fosfomycin
  • levamolin
  • Metronidazole (Flagyl, Amrizol, and their like)
  • mupirocin
  • nitrofurantoin
  • tigecycline

How do doctors choose the appropriate antibiotic for each infection?

Each antibiotic, or at least each antibiotic group, is effective in eliminating certain types of bacteria of its own, and therefore your doctor determines the appropriate antibiotic for each case according to patient’s medical history and medical examination that guides him to the type of bacteria that is likely to cause infection and disease.

The best way to determine the appropriate antibiotic for an infection is to identify in the laboratory the type of bacteria causing the disease by taking a sample of urine, blood, sputum, or part of the tissue of the affected organ and then making a culture in the specialized laboratory to determine the type of bacteria causing the disease and the antibiotic to which it responds.

The disadvantage of the previous method (the culture) is that it is expensive and takes a few days to show its results, so it is used only in cases that are resistant to the usual treatment or atypical infection, and it is also possible to combine the usual method by giving the patient the closest antibiotic expected to be effective while waiting for the result of the culture and the change On the basis of its outcome later.

An antibiotic that is effective against bacteria in the laboratory is not necessarily effective against the same bacteria in the patient's body, because there are factors that determine the effectiveness of antibiotics in different circumstances.

What are the factors that determine the effectiveness of an antibiotic?

  • Quality of absorption of the antibiotic into the blood after administration (if the patient takes it orally as tablets or syrup).
  • The distribution of the antibiotic in the body and the percentage of its delivery at the site of infection.
  • How quickly the body gets rid of antibiotic residues.
  • Taking other medications with the antibiotic.
  • Having a chronic disease.
  • Age.
The above factors differ from person to person, which makes the effectiveness of antibiotics different from person to person.

When a doctor chooses an antibiotic for a patient, he considers the following factors:

  • The nature and severity of the infection
  • The condition of the patient’s immune system and whether it is healthy and can help eliminate bacteria, or does he suffer from immunodeficiency and needs customized doses.
  • The side effects of the antibiotic and its comparison with the general condition of the patient, especially the conditions of the liver and kidneys.
  • If the patient is allergic to a particular type of antibiotic.
  • The cost of the antibiotic is also taken into consideration according to the patient's standard of living.

Antibiotic resistance

Because of the widespread use and misuse of antibiotics, the exposure of all kinds of bacteria to these antibiotics has increased, and although most bacteria are killed when exposed to antibiotics, some of them survive and develop methods that enable them to resist the effect of the antibiotic.

For example, 50 years ago, Staphylococcus aureus, which is one of the most important causes of skin infections, was very sensitive to penicillin and was eliminated completely by the appropriate dose of penicillin, but with time it developed an enzyme capable of breaking down penicillin and hindering its effectiveness, so these strains are now resistant to normal penicillin.

Fortunately, scientists were able to modify penicillin by adding substances capable of blocking the effect of that enzyme  and thus was able to eliminate the aureus bacteria, but unfortunately, after a few years these bacteria were able to adapt and became resistant also to the modified penicillin.

Causes of escalating antibiotic resistance include:

  • Misuse of antibiotics in treatment of diseases that are not caused by bacteria.
  • Mothers demanding antibiotics for their children for trivial viral infections.
  • Not following the doctor’s instructions for the duration of treatment.

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