Prevalence of multidrug-resistant organisms in intensive care unit patients and rate of subsequent bacteraemia: a 5-year study

Introduction:
Multidrug-resistant organism (MRO) bacteraemia is associated with significant mortality. A limited number of studies have examined the relationship between MRO colonisation and subsequent bacteraemia in critically ill patients.

Material and methods:
All patients with a positive surveillance swab result and a positive blood culture result for MROs admitted to the Westmead intensive care unit (ICU) between 1 January 2014 and 31 March 2019 had their results matched with ICU data extracted from the ICU database and analysed for the risk of bacteraemia among swab positive patients.

Results:
There were 3,878 (2,388 males, 1,490 females) assessable admissions during the period. The median APACHE II (Acute Physiology and Chronic Health Evaluation) score was 17. A total of 9,681 swab results were collected from 3,878 patients. Of the 3,878 patients, 818 were positive for MROs, and 3,060 were negative. Thirty-two swab positive patients (3.9%) tested positive for MROs in the blood culture, and 16 (0.52%) in the swab negative group had MROs in their blood cultures. This difference was statistically significant (adjusted [adj] OR 6.33; 95% CI: 3.40–11.76). The swab positive group was also associated with a significantly higher positive blood culture with orga­nisms other than MROs than the swab negatives (11.1% and 6.2%, respectively, adj OR 1.37; 95% CI: 1.04–1.82). The overall mortality was higher in swab positive compared to swab negative patients (20.7% vs. 13.1%, P < 0.001). The overall prevalence of MRO colonisation was 21% in our cohort.

Conclusions:
The risk of MRO bacteraemia was higher among patients with a positive surveillance swab result for the organism compared to those with a negative swab, but this was not associated with higher mortality in that group.