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

Abstract Carbapenem-resistant Enterobacterales have become a major public health issue worldwide. Here we present an outbreak caused by a clonal multidrug-resistant Proteus mirabiis strain producing VIM-4 metallo-β-lactamase (MBL) and TEM-2 in a Greek tertiary hospital. From July 2015 to February 2016, 27 imipenem-resistant P. mirabilis isolates were recovered from 14 patients hospitalized in AHEPA University Hospital, Thessaloniki. The isolates were either susceptible or resistant to meropenem and resistant to all remaining β-lactams but aztreonam. Phenotypic and molecular analysis revealed that all isolates harboured a blaVIM-4 MBL. Resistome analysis of a representative isolate showed the presence of one IncQ1 plasmid that harboured the VIM-4 carbapenemase and TEM-2 β-lactamase among 18 resistance genes coding for resistance to β-lactams, aminoglycosides, trimethoprim, sulphonamides and lincozamines. Genotyping by pulsed-field electrophoresis (PFGE) revealed that the isolates were epidemiologically related. After the recovery of the index carbapenemase-producing P. mirabilis clinical isolates 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 intensive care units (ICUs). The outbreak was finally interrupted six months later. This is the first documentation of VIM-4 MBL in P. mirabilis as well as the first hospital outbreak caused by an MBL-producing P. mirabilis strain.