Metallo-β-lactamases among Enterobacteriaceae from routine samples in an Italian tertiary-care hospital and long-term care facilities during 2008

Abstract The emergence of metallo-β-lactamase (MBL)-producing Enterobacteriaceae is a serious public health concern. Producers have been repeatedly isolated from patients and long-term care facility (LTCF) residents around Bolzano, and we sought to assess their prevalence and clinical impact. All routine Enterobacteriaceae isolates from a Bolzano tertiary-care hospital and associated long-term care facilities in 2008 ( n = 5500) were screened for MBLs, with case details reviewed for the source patients. In total, 36 producers were obtained from 29 patients, comprising 14 Escherichia coli , six Klebsiella pneumoniae , four Klebsiella oxytoca , four Citrobacter freundii , two Enterobacter cloacae and two Morganella morganii , as well as single Citrobacter amalonaticus, Enterobacter aerogenes, Providencia stuartii and Proteus mirabilis isolates. All were PCR-positive for bla VIM and 25 were PCR-positive for qnrS ; 19 non- K. pneumoniae had bla SHV and one had bla CTX-M-group1 ; 13 were from 12 LTCF residents and 23 were from 17 acute-care patients. All these patients had serious underlying diseases with prolonged hospitalization or LTCF stay; only seven had infections due to the MBL producers, comprising four urinary tract infections, two catheter-related bloodstream infections and one patient with both a surgical site infection and pneumonia. Five patients had more than one MBL-producing organism. Pulsed-field gel electrophoresis identified a cluster of six related E. coli , whereas pairs of K. pneumoniae and C. freundii isolates had >85% profile similarity. Transformants prepared from two isolates were shown to be PCR-positive for bla VIM , qnrS and bla SHV ; their plasmids gave similar restriction fragment length polymorphism patterns, and bla VIM-1 , qnrSI and bla SHV-12 were detected by sequencing.