Bacteria that are difficult to treat due to the so-called NDM gene primarily drove the increase, CDC researchers wrote in an article published Monday in the Annals of Internal Medicine. In recent years, the CDC has drawn attention to “ nightmare bacteria ” resistant to a wide range of antibiotics. They counted 4,341 cases of carbapenem-resistant bacterial infections from those states in 2023, with 1,831 of them the NDM variety. But the rate of NDM cases rose from around 0.25 to about 1.35 — an increase of 460%, the authors said. A CDC report published in June noted an increase in NDM cases in New York City between 2019 and 2024.