Emergence and global spread of Listeria monocytogenes main clinical clonal complex

Retracing microbial emergence and spread is essential to understanding the evolution and dynamics of pathogens. The bacterial foodborne pathogen Listeria monocytogenes clonal complex 1 ( Lm -CC1) is the most prevalent clonal group associated with listeriosis, and is strongly associated with cattle and dairy products. Here we analysed 2,021 Lm -CC1 isolates collected from 40 countries, since the first Lm isolation to the present day, to define its evolutionary history and population dynamics. Our results suggest that Lm -CC1 spread worldwide from North America following the Industrial Revolution through two waves of expansion, coinciding with the transatlantic livestock trade in the second half of the 19th century and the rapid growth of cattle farming in the 20th century. Lm -CC1 then firmly established at a local level, with limited inter-country spread. This study provides an unprecedented insight into Lm -CC1 phylogeography and dynamics and can contribute to effective disease surveillance to reduce the burden of listeriosis. ### Competing Interest Statement The authors have declared no competing interest.