Infections with VIM-1 metallo-β-lactamase-producing Enterobacter cloacae and their correlation with clinical outcome

The aim of this study was to ascertain the incidence and clinical significance of metallo-β-lactamases among Enterobacter strains isolated from patients with nosocomial infections. We prospectively collected data on patients with Enterobacter infection during a 13-month period. All of the strains were investigated for antibiotic susceptibility, the presence and expression of metallo-β-lactamases, and clonality. Of 29 infections (11 involving the urinary tract, 7 pneumonias, 3 skin/soft tissue infections, 3 intra-abdominal infections, 3 bacteremias, and 2 other infections), 7 (24%) were caused by Enterobacter cloacae strains harboring a bla VIM-1 gene associated or not with a bla SHV12 gene. Infections caused by VIM-1-producing strains were more frequently associated with a recent prior hospitalization ( P = 0.006), cirrhosis ( P = 0.03), relapse of infection ( P < 0.001), and more prolonged duration of antibiotic therapy ( P = 0.01) than were other infections. All of the isolates were susceptible to imipenem and meropenem and had bla VIM-1 preceded by a weak P1 promoter and inactivated P2 promoters. Most VIM-1-producing Enterobacter isolates belonged to a main clone, but four different clones were found. Multiclonal VIM-1-producing E. cloacae infections are difficult to diagnose due to an apparent susceptibility to various beta-lactams, including carbapenems, and are associated with a high relapse rate and a more prolonged duration of antibiotic therapy.