Question: Will all bacteria eventually become resistant to current antibiotics?

Marialuisa Crosatti answered on 4 Mar 2019:

The rising of antibiotic resistance has grubbed the newspapers and TV news headlines in the last few years. And it is right to be worried about it. In essence, bacteria are already developed resistant to all type of antibiotics including the latest developed. Likely, not all bacteria in the world present resistance to all antibiotics. Bacteria are divided based on species names but within each species they are also divided in strains. Strains belonging to the same species have general characteristics in common that define that bacterial species but they also differ from each other. Often, the difference is due to the ability to survive higher level of antibiotics. This means that not all the strains within a species are resistant to antibiotics and different strains will be resistant to different antibiotics.
Unfortunately, it usually takes only one or two genes to confer resistance to antibiotics and these genes are found on parts of bacterial genome (such as plasmids, genomic islands) that may be transferred from one strain to the next often between different species. In fact, there are some type of bacteria known to being accumulating antibiotic-resistant conferring genes. For example, some of the strains belonging to Acinetobacter baumannii are known to have part of they DNA or genome (known as genomic islands) packed full with genes increasing their levels of resistance to antibiotics and making therapy for infections very problematic.
Given enough time and environments where different type of bacteria may “meet” each other and lose/acquire part of their genomes, it could be possible in theory for all bacteria to become resistant to all antibiotics. However, this process would need to confer an evolutionary advantage in specific living conditions and for the bacteria to retain these abilities, it would require all antibiotics to be present in the environment all the time.