Nosocomial outbreak by imipenem-resistant metallo-beta-lactamase-producing Pseudomonas aeruginosa in an adult intensive care unit in a Brazilian teaching hospital

Enferm Infecc Microbiol Clin. 2009 May;27(5):269-74. doi: 10.1016/j.eimc.2008.09.009. Epub 2009 Apr 21.


Objective: To describe an outbreak of imipenem-resistant metallo-beta-lactamase-producing Pseudomonas aeruginosa, enzyme type bla, by horizontal transmission in patients admitted to a mixed adult ICU.

Methods: A case-control study was carried out, including 47 patients (cases) and 122 patients (control) admitted to the mixed ICU of a university hospital in Minas Gerais, Brazil from November 2003 to July 2005. The infection site, risk factors, mortality, antibiotic susceptibility, metallo-beta-lactamase (MBL) production, enzyme type, and clonal diversity were analyzed.

Results: A temporal/spatial relationship was detected in most patients (94%), overall mortality was 55.3%, and pneumonia was the predominant infection (85%). The majority of isolates (95%) were resistant to imipenem and other antibiotics, except for polymyxin, and showed MBL production (76.7%). Only bla SPM-1 (33%) was identified in the 15 specimens analyzed. In addition, 4 clones were identified, with a predominance of clone A (61.5%) and B (23.1%). On multivariate analysis, advanced age, mechanical ventilation, tracheostomy, and previous imipenem use were significant risk factors for imipenem-resistant P. aeruginosa infection.

Conclusions: Clonal dissemination of MBL-producing P. aeruginosa strains with a spatial/temporal relationship disclosed problems in the practice of hospital infection control, low adherence to hand hygiene, and empirical antibiotic use.

MeSH terms

  • Brazil
  • Case-Control Studies
  • Cross Infection / epidemiology*
  • Disease Outbreaks*
  • Drug Resistance, Bacterial
  • Female
  • Hospitals, Teaching
  • Humans
  • Imipenem / pharmacology*
  • Intensive Care Units*
  • Male
  • Middle Aged
  • Pseudomonas Infections / epidemiology*
  • Pseudomonas aeruginosa / drug effects*
  • Pseudomonas aeruginosa / enzymology*
  • beta-Lactamases / biosynthesis*


  • Imipenem
  • beta-Lactamases