In a follow-up on the “superbug” NDM-1 outbreak reported in Tuscany, the Regional Health Agency (ARS Toscana) reports the outbreak of New Delhi metallo-beta-lactamase (NDM)-producing carbapenem-resistant Enterobacterales that started in the north-western area of ​​Tuscany, Italy, continues into 2021.


The outbreak is mainly due to Klebsiella pneumoniae ST147 carrying the blaNDM-1 gene. In 2020, NDM-9-producing  were isolated in the same geographical area.

Between November 2018 and January 3, 2021, NDM bacteria in Tuscany were isolated in the blood of 323 patients . The cases were fatal in 25% of patients with sepsis  (not necessarily deaths due to the specific infection), a percentage comparable to the lethality for this condition caused by other bacteria resistant to carbapenem antibiotics. 

The spread of NDM bacteria has involved numerous hospitals, in particular those of Lucca, Livorno, Massa-Carrara, Pisa and Pontedera: in most cases it was colonization (i.e. the patients have no disease, but are equally capable of spread these microorganisms), but there have also been cases of serious infections in already compromised patients.

mcr-1 gene: An interview with Dr Judy Stone

New Delhi Metal beta-lactamase is an enzyme produced by bacteria in the gut, capable of destroying many types of antibiotics . Drugs that are rendered ineffective include  carbapenems , a class of antibiotics used for severe infections. 

The outbreak of NDM in Tuscany is attributable to a prevalent bacterial clone which, compared to NDMs described in the literature, resistant to all β-lactam antibiotics except aztreonam, have incorporated other resistance genes that make them resistant also to aztreonam, aminoglycosides and ceftazidime / avibactam.