A fascinating study from a European research group has unravelled the molecular epidemiology of a large European collection of carbapenem-resistant Klebsiella pneumoniae clinical isolates. Most carbapenem resistance was due to an acquired carbapenemases, transmission clusters were common within and between hospitals, carbapenemase-producing isolates are more likely to spread in hospitals, and 21 SNPs is the magic number for defining CPE person-to-person transmission using WGS.