New research reveals that bacteria can develop antibiotic resistance in a surprisingly short time frame, from instantaneous to several days. This rapid evolution is due to the ability of some bacteria to divide rapidly, passing on genetic changes that provide resistance. While resistance mechanisms take varying amounts of time to emerge, scientists are working to overcome this challenge through the use of combination therapies and a better understanding of antibiotic penetration.

Source: https://www.livescience.com/health/viruses-infections-disease/how-fast-can-antibiotic-resistance-evolve