Bacteria can be resistant to one or more antibiotics, that is, they develop resistance to the particular antibiotics. This resistance results from random mutations that confer a survival advantage on the affected bacterium when there is an appropriate selection pressure. Resistance then spreads rapidly. If the corresponding resistance genes are also located on plasmids (ring-shaped DNA structures), antibiotic resistance can also spread very rapidly between different species through an exchange of these plasmids. This is particularly the case when different bacterial species are found in the same environment, e.g. the soil, the intestines, waste water, biofilms, etc.
There are different types of antibiotic resistance, e.g.
- primary resistance (an antibiotic lacks efficacy for certain bacteria)
- secondary resistance (loss of efficacy of an antibiotic in a non-primarily resistant bacterium due to a mutation or an exchange of genetic material with others)
- multidrug resistance is the absence of susceptibility of a bacterium to several antibiotics from different classes
Antibiotic resistance is a problem with grave consequences. It is therefore important to reduce the inappropriate use of antibiotics.