Outbreak of Citrobacter freundii carrying VIM-1 in an Italian Hospital, identified during the carbapenemases screening actions, June 2012

Objective: The identification of patients colonized or infected with carbapenemase-producing Enterobacteriaceae (CPE), in order to control and prevent the global spread of multidrug-resistant (MDR) pathogens. Methods: From June 1 to June 15, 2012, eight Citrobacter freundii strains with reduced susceptibility to carbapenems were isolated from rectal swabs of hospitalized patients during active screening following the detection of a Klebsiella pneumoniae carbapenemase (KPC) -positive patient on the ward. All isolates were analyzed phenotypically and molecularly by PCR and sequencing. Genotype clustering was performed by multilocus sequence typing (MLST) analysis. Results: The isolates showed high rates of multidrug resistance profile. A phenotypic assay for carbapenemase production suggested the presence of metallo-b-lactamase (MBL). The blaVIM-1 gene was detected in all imipenem-resistant C. freundii isolates. MLST showed that the C. freundii isolates shared the same sequence type (ST). Phylogenetic analysis revealed a strict relationship with an ST5 C. freundii isolate from a diarrhea patient in China. Conclusions: Our findings showed that the active surveillance program for CPE was useful, not only for the detection of KPC-producers, but also to identify and control the spread of other MDR pathogens that could expand the spectrum of circulating MDR pathogens.