Antibiotic resistant bacteria

Invisible to the naked eye and occurring in vast numbers almost everywhere you look, disease-spreading bacteria are a frightening prospect! But what makes them even more alarming is their innate ability to overcome the medicines we use to prevent bacterial infections. This phenomenon is called antibiotic resistance. Antibiotic resistance within bacteria arises from the increased exposure of microorganisms to antibiotics and these microorganisms’ naturally occurring resistance response. This antibiotic resistance in bacteria is prevalent in modern society because of the exponential increase in antimicrobial medicine usage over the last few decades. Keep reading to learn more about the evolution of antibiotic resistance in bacteria, the meaning, and more.

The Meaning of Antibiotic-Resistant Bacteria

Bacteria are single-celled organisms which are found everywhere you look! They thrive in warm, moist, nutritious conditions but can be found even in the most extreme temperature and pressure environments on earth. Some bacteria are beneficial.

Certain bacterial microorganisms will cause disease, and some are even fatal. To counteract these disease-spreading organisms, scientists have developed antibiotics, which are antimicrobial drugs that help kill exclusively bacterial cells in our body without targeting our own cells! Despite the best efforts of antibiotics, clever bacteria often overcome the advances of these drugs by mutating and developing drug resistance mechanisms, continuing to cause disease.

Evolution of antibiotic resistance in bacteria

Cumulative mutations in a species’ genome provide crucial genetic variation in a population and enable species to survive under selective evolutionary pressures.

These microbes are constantly battling to survive against the antibiotics we take to kill them. Mutations in the gene sequence of bacteria can lead to them displaying different characteristics, some of which may be beneficial in defending against the effects of antibiotics. The fact that bacteria multiply at a rapid rate means that mutations within populations can quickly spread.

This is the process by which bacteria become resistant to antibiotics:

1. An antibiotic is introduced to the body after the person has become infected by a specific bacteria.

2. The population of bacteria is constantly growing, and random mutations within the population are continually occurring.

3. Some of these mutations may cause the bacteria to exhibit characteristics beneficial in resisting antibiotic effects.

4. These bacteria which contain the beneficial mutant gene will survive within the population, and because of bacteria’s ability to reproduce rapidly, they will become more prevalent in the population.

5. The antibiotic kills off the bacteria without the mutant gene, so there is less competition for the bacteria with the mutant gene.

6. The bacteria containing the mutant gene are now dominant within the population, so the antibiotic has little to no effect on the growth of the population. Therefore the ill person does not recover.

These new antibiotic-resistant strains can be an issue because the prescribed antibiotic for the original bacteria will no longer work, so the disease will more easily spread. This is a natural process amongst all bacteria but is becoming a serious public health crisis because of antibiotic overuse and misuse, which creates selective pressure for spreading superbugs. These microbes are much more difficult to kill!

Fig. 2 - Steps of antibiotic resistance

Bacteria and natural selection

The development of antibiotic-resistant strains in bacteria is a comprehensive source of evidence for Darwin’s theory of evolution, as it displays natural selection. This natural selection is exhibited by the ‘fitter’ population of bacteria surviving and reproducing when the antibiotic is present, whereas the less ‘fit’ population of bacteria without the resistant strain will decrease in the presence of the antibiotic.