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Keywords:

  • Pseudomonas aeruginosa;
  • outbreak;
  • colonization;
  • intensive care unit;
  • mortality

Background:  Contaminated oral swabs caused a nationwide monoclonal Pseudomonas aeruginosa outbreak involving 27 Norwegian hospitals. The aim of the study was to study the consequences on mortality and morbidity of the introduction of this P. aeruginosa strain to intensive care unit (ICU) patients.

Methods:  Forty-four out of 96 patients admitted to the general ICU of Akershus University Hospital during the outbreak, ventilated for more than 24 h and with at least one microbiological sample, were included and followed until death or hospital discharge. All isolated P. aeruginosa strains were genotyped. Demographic data, admission diagnosis, Simplified Acute Physiology Score II (SAPS II), Sequential Organ Failure Assessment (SOFA) score, comorbidities, and antibiotics used in the first week were recorded.

Results:  The outbreak strain was found in 18 patients (41%) of whom seven became infected. Median time to the first positive culture was 4 days. These 18 patients spent a significantly longer time on mechanical ventilation (P =0.03) and had a significantly higher hospital mortality, 55.5% vs. 19.2% (P =0.03), than non-colonized patients. The number of patients with severe underlying disease was significantly higher (P =0.01) and the decline in SOFA score was significantly slower in the pseudomonas group (P =0.02). Irrespective of colonization status, patients with severe underlying disease had a significantly higher mortality (58%) than those without (16%) (P =0.009).

Conclusion:  Use of contaminated oral swabs led to a high rate of early airways colonization. Patients with severe underlying disease were more likely to become colonized, but whether colonization has any influence on hospital mortality requires further study.