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Objectives: To describe the first nosocomial outbreak of Pseudomonas aeruginosa producing SPM-1 metallo-[beta]-lactamase (MBL) in southern Brazil.

Patients and methods: From January to October 2004, carbapenem-resistant P. aeruginosa (CRPA) were recovered from hospitalized patients. Mortality, site of infection/colonization, patient location and susceptibility profiles were analysed. A sample of CRPA was screened for MBL production, evaluated for the presence of blaSPM-1, blaIMP-1 and blaVIM-2 genes by PCR and submitted for molecular typing by DNA macrorestriction.

Results: A total of 135 CRPA (one isolate per patient) were recovered. Two major antibiotic susceptibility profiles comprised 63.7% of the isolates (susceptibility to polymyxin B and aztreonam, and susceptibility only to polymyxin B). Thirty-five CRPA were screened for MBL production (10 isolates from April, June and July, and 25 from September and October) and 27 (77.1%) proved to be positive for MBL production. Twenty-one of the 24 CRPA tested carried the blaSPM-1 gene. The mortality of patients with CRPA was 48.1% and no variable was associated with death. Molecular typing revealed the presence of a clone with four related subtypes among the blaSPM-1-positive CRPA.

Conclusions: The prevalence of MBL production by CRPA is high and horizontal transmission is a major determinant for the spread of SPM-1 CRPA among patients in this institution. As infection control measures failed to control the spread of CRPA, continuous surveillance for MBL production is warranted.

(C) British Society for Antimicrobial Chemotherapy 2005. Published by Oxford University Press. All rights reserved.