Background We report on an outbreak in a surgical, interdisciplinary intensive
care unit (ICU) of a tertiary care hospital. We detected a cluster of ICU
patients colonized or infected with multidrug-resistant Pseudomonas
aeruginosa. We established an outbreak investigation team, performed an
exploratory epidemiological analysis and initiated an epidemiology-based
intervention. Methods As part of the outbreak investigation, we performed
microbiological examinations of the sinks in the patient rooms and a
retrospective case-control study. All patients admitted to the outbreak ICU
between January 2012 and February 2014 were included. Cases were patients
colonized with the outbreak strain. Controls were patients with a different
Pseudomonas aeruginosa strain. Risk factors were evaluated using multivariable
conditional logistic regression analysis. Strain typing was performed using
the repetitive element-based polymerase chain reaction (rep-PCR) DiversiLab
system. Results The outbreak strain was found in the sinks of five (of 16)
patient rooms. Altogether 21 cases and 21 (randomly selected) controls were
included. In the univariate analysis, there was no significant difference in
baseline data of the patients. In the multivariate analysis, stay in a room
with a colonized sink (Odds Ratio[OR] 11.2, p = 0.007) and hemofiltration (OR
21.9, p = 0.020) were independently associated with an elevated risk for
colonization or infection by the outbreak strain. In a subsequent evaluation
of the work procedures associated with hemofiltration, we found that the
ultra-filtrate bags had been on average five times per day emptied in the
sinks of the patient rooms and were used multiple for the same patient. We
exchanged the traps of the contaminated sinks and eliminated work procedures
involving sinks in patient rooms by implementation of single use bags, which
are emptied outside patient rooms to reduce splash water at the sinks. In the
20 month follow-up period, the outbreak strain was detected only once, which
indicated that the outbreak had been ceased (incidence 0.75% vs. 0.04%, p <
0.001) Furthermore, the incidence of Pseudonomas aeruginosa overall was
significantly decreased (2.5% vs. 1.5%, p < 0.001). Conclusion In ICUs,
limiting work processes involving sinks results in reduced multidrug-resistant
Pseudomonas aeruginosa rates. ICUs with high rates of Pseudomonas aeruginosa
should consider eliminating work processes that involve sinks and potentially
splash water in close proximity to patients. Trial registration All data were
surveillance based data which were obtained within the German Law on
Protection against Infection (“Infektionsschutzgesetz”). Therefore a trial
registration was not required
