Studies showed that bacteria, such as E. coli have proteins present that helps pump out toxic chemicals within the bacterial cell. This allows the microbes to become resistant to antibiotics. AcrAB-TolC is the pump that bacterial cells have, while it does not get rid of antibiotics within the cell it moves enough of the antibiotics out of the cell in order to produce resistance proteins. To find out how bacteria pass antibiotic resistance on, researchers at University of Lyon used genetically engineered E.coli (making them fluorescent). Under the microscope it could be observed that the bacteria swaps plasmid passing on the characteristics of antibiotic resistance.
At times it is frightening to read about how fast bacteria and viruses grow, hence evolving quicker. While an antibiotics have been created, it is amazing to see how bacteria can find a way to become resistant. It is almost like a constant battle!