Bacteria can become resistant to antibiotics in many different ways. For instance, spontaneous mutation, in which bacteria becomes resistance over different generations. In this case, the plasmid in the cells DNA carries the resistant gene. Moreover, the plasmid also produces a protein which helps flush out antibiotics from the cell. Other ways are transformation, transduction as well as conjugation. Lastly, the overuse of antibiotics and over cleanliness also play a role in this since this leads to the kill of non-resistant bacteria which leads to the bacteria which survives to mutate.
