Antibiotic Resistance

Bacterial resistance to antibiotics is a very serious problem that is becoming more and more threatening. Antibiotics are considered to be one of the most significant medical discoveries of the 20th century and their widespread usage led to disappearance of many diseases in civilized countries. The growing ability of bacteria to become immune against the antibiotics is therefore a dreaded phenomenon (the so-called MRSA is the classic infection).


Bacteria are single-cell organisms with significant differences from cells of animals and plants. This difference is important for antibiotic usage as the antibiotics damage bacterial cell, but do not harm the cells of the organism (or cause only minor damage compared to destroyed bacteria).


Bacterial cell carries DNA molecules that code specific properties of the bacteria. The DNA in the bacterial cell is stored in a single central circular DNA (primitive analogue of cell nuclei of animal and human cells) and within multiple small circular DNA molecules called plasmids. Genetic information is unique for each bacterium. It enables daily survival of the bacterial cell, production of various substances, metabolic control, etc. Unfortunately, some bacteria have in their genetic information special genes that enable them to resist against certain antibiotics.


The real disaster is a great plasticity of plasmids. The plasmids within the cell can variously combine, copy and they may be even incorporated into the central circular DNA. In addition, the DNA can be transferred between bacterial cells. It is difficult to say to what extent this is a random process, but it occurs constantly. If there is a single bacterium gene for resistance against a certain antibiotic, it can easily and rapidly spread among the bacterial population. The bacteria are also able to accumulate more antibiotic-resistant genes and become resistant against multiple antibiotics (multidrug-resistant bacteria).


Darwin's theory of natural selection explains why the antibiotic-resistant bacteria spread more than before. The invisible world of bacteria is alive and it is in constant motion. Everywhere around us and even in our bodies there are many of bacterial strains that compete and fight for survival. According to Darwin's theory, the best chance of survival has such individual with the most useful characteristics determined by genetic information. Frequent use of antibiotics creates an unwanted selection. The antibiotic-sensitive bacteria die, but the resistant survive and multiply.


The above paragraphs can be summarized in the following points:

  1. Some bacteria have genetically determined ability to defend against certain antibiotics.
  2. This ability can be transferred to other bacteria of the same group, or even to other bacterial species.
  3. Widespread usage of antibiotics has created an evolutionary pressure in favor of resistant bacteria causing their numbers to increase at the expense of antibiotic-sensitive bacteria.
  4. There exist bacteria resistant to multiple types of antibiotics.

The antibiotic resistance is nothing new. Bacterial strains resistant to a specific antibiotic have been noticed already by Alexander Fleming, who stood at the birth of modern antibiotic therapy. Due to the irresponsible use of antibiotics, however, the number of resistant bacteria increases and it begins to complicate the treatment of infectious diseases. We can create new generations of antibiotics, but it is a lengthy and expensive process and the resistance spreads very quickly. The bacteria are always one step ahead of us.


The situation is dangerous, but far from hopeless. Antibiotic resistance may emerge, but it can also disappear. It is important to prescribe and use antibiotics wisely only when it is needed (more can be read in the text about CRP). Furthermore, it is good not to prescribe only one type of the antibiotic, but change them regularly. When a resistant strain of bacteria occur in a certain location, it is wise to stop using the antibiotic for a period of time and switch it for another type.


The microbiological laboratories can help us by evaluating the bacterial resistance. The laboratory can examine samples from the patient’s body (usually some body fluids) and not only confirm bacterial presence, but also determine the sensitivity against commonly used antibiotics. This helps us to choose the best antibiotic, which the particular bacterium is most sensible to.


For a person like me who is not expert in the field of microbiology, it is not easy to predict further development. Yet even in my short medical practice, I can confirm relatively frequent cases of patients where the antibiotic resistance disrupted the therapy or even endangered their lives. The main question is, if the production of new antibiotics and the current rationalization of antibiotic therapy will lead to a reversal of the unfortunate trend of increasing resistance.


Jiri Stefanek, MD  Author of texts: Jiri Stefanek, MD
 Sources: basic text sources