A plausible worst-case scenario of increasing multidrug resistance as a tool for assessing societal risks and capabilities in Sweden.

A "plausible worst-case scenario" of a gradually increasing level of multidrug-resistant bacteria (carbapenem-resistant E. coli) in the human population was developed and used to study how Swedish authorities would manage this situation and to identify preventive measures that could be taken. Key findings include: (1) a scenario in which 5% of the population in southern Sweden become carriers of carbapenem-resistant E. coli is possible or even likely in 10 to 15 years; (2) it is not clear when and how the increase of E. coli resistant to carbapenems as in the scenario would be detected in the general human population; (3) identified negative consequences of the scenario on society were primarily due to increased demands on the healthcare system and potential consequences for food-producing animals, food safety, and environmental health; and (4) a number of preventive and mitigation measures were suggested, including initiating long-term screening programs for public and animal health as well as for food and water production to monitor increasing levels of carbapenem resistance. Strategies and plans to prevent and handle future increasing prevalence of multidrug-resistant bacteria need to be developed.