NDM- or VIM-producing Citrobacter spp. in Poland, 2011-19: high genetic diversity with broader representation of ST8, ST18 and ST22 global clones.

Abstract

This study focused on genomic epidemiology of metallo-β-lactamase (MBL)-producing Citrobacter spp. in Poland. It included 118 isolates with VIM (n = 100), NDM (n = 17) or IMP (n = 1) enzymes from 2011 to 19, largely C. freundii (n = 94) of 33 sequence types (STs). Three globally-spread STs were more prevalent, namely ST18 (n = 15), ST8 (n = 11) and ST22 (n = 10), each diversified clonally and by VIM and NDM determinants. Only few outbreaks were evidenced, indicating MBL presence to result mainly from independent acquisitions, consistent with co-identifications of Citrobacter isolates (n = 12) with other MBL-producing Enterobacterales. Despite lower outbreak potential, Citrobacter spp. constitute a significant MBL reservoir, requiring attention and surveillance.