Clonal outbreak caused by VIM-4-producing Proteus mirabilis in a Greek tertiary-care hospital.

Carbapenem-resistant Enterobacterales have become a major public-health issue worldwide. Here we report an outbreak caused by a clonal multidrug-resistant Proteus mirabilis strain producing VIM-4 metallo-β-lactamase (MBL) and TEM-2 β-lactamase in a Greek tertiary-care hospital. From July 2015 to February 2016, 27 imipenem-resistant P. mirabilis isolates were recovered from 14 patients hospitalised in two intensive care units (ICUs) and the internal medicine department in AHEPA University Hospital, Thessaloniki. The isolates were either susceptible or resistant to meropenem and were resistant to all remaining β-lactams except aztreonam. Phenotypic and molecular analysis revealed that all of the isolates harboured a bla MBL gene. Resistome analysis of a representative isolate showed the presence of an IncQ1 plasmid harbouring the bla carbapenemase and bla β-lactamase genes among resistance genes coding for resistance to β-lactams, aminoglycosides, trimethoprim, sulfonamides and lincosamides. Genotyping by pulsed-field electrophoresis (PFGE) revealed that the isolates were epidemiologically related. After recovery of the index carbapenemase-producing P. mirabilis clinical isolate, infection control measures were intensified in the affected departments. Rectal sampling for carbapenem-resistant bacteria was initiated on a weekly basis among patients admitted to the general ICU. The outbreak was finally interrupted 6 months later in February 2016. This is the first documentation of the bla MBL gene in P. mirabilis as well as the first hospital outbreak caused by a MBL-producing P. mirabilis strain.