The paper disks have different antibiotics:
♦ Antibiotics in the discs in the culture on the left prevent bacteria from proliferating.
♦ Bacteria in the culture on the right are resistant to most of the antibiotics.

Antibiotics kill certain types of bacteria. Over time, those bacteria change to develop a resistance to the antibiotics. Called antibiotic resistance, this is one of the most serious problems facing modern surgery and medicine. It is also one of the best examples of evolution in action.

Antibiotic resistance spreads very quickly, far faster than microbiologists expected. "As long as new drugs keep coming, resistance is not a problem. But there has not been a new class of antibiotics discovered since the 1980s".