An outbreak of infection due to metallo-ß-lactamase-producing Proteus mirabilis in the surgical intensive care unit

Abstract

Background. We described an emerging outbreak of infection caused by metallo--lactamase (MBL)-producing Proteus mirabilis that occurred in the surgical ICU of a Serbian university hospital, and assessed this outbreak in a retrospective observational study. Methods. Records from patients in this ICU who had MBL-producing P. mirabilis isolates were reviewed retrospectively. All enterobacterial isolates from clinical specimens (one per patient) were tested for MBL production. We used a multiplex PCR assay to detect and differentiate each of the MBL gene families: IPM, VIM, SPM, GIM and SIM. In July and in November 2008, we conducted a point prevalence survey of rectal colonization with MBL-producing P. mirabilis. Results. From June through November, 2008, nine patients in the surgical ICU were infected by MBL-producing P. mirabilis. These isolates exhibited multi-drug resistance. The outbreak was discovered in June and expanded rapidly; ten of twelve (83%) patients in ICU were colonized with outbreak strains in July. Seven cases of bacteremia, including 3 intravascular catheter related, one surgical site infection, and one urinary tract infection were identifi ed. Six of nine MBL-positive P. mirabilis strains belonged to the IPM family, and three others belonged to the VIM family. Actual mortality was 56%, but we could not determine mortality indirectly attributable to the infection. Conclusion. The rapid emergence of MBL-producing P. mirabilis within a Serbian hospital created a challenge for clinicians, microbiologists, and epidemiologists. This resistant infection added further to the established cases of antimicrobial resistance within the hospital.