Antibiotic susceptibility research. Microbiologist holding two Petri dish culture plates growing bacteria in the presence of discs containing various antibiotics. The bacteria on the left plate is not growing around the discs and is therefore susceptible to the antibiotics on the discs. The plate on the right was inoculated with a Carbapenem-Resistant Enterobacteriaceae (CRE) bacterium that proved to be resistant to all of the antibiotics tested and is therefore able to grow near the discs. Photographed at the Centers for Disease Control (CDC), USA.