Comparison of Daily versus Admission and Discharge Surveillance Cultures for Multidrug-Resistant Organism Detection in an Intensive Care Unit

Abstract

Background: Admission and discharge screening of patients for asymptomatic gut colonization with multidrug-resistant organisms (MDROs) is a traditional approach to active surveillance, but its sensitivity for detecting colonization is uncertain.

Methods: Daily rectal or fecal swab samples and clinical data were collected over 12 months from patients in one 25-bed intensive care unit (ICU) in Chicago, IL USA and tested for the following multidrug-resistant organisms (MDROs): vancomycin-resistant enterococci (VRE); third-generation cephalosporin-resistant Enterobacterales, including extended-spectrum β-lactamase-producing Enterobacterales (ESBL); and carbapenem-resistant Enterobacterales (CRE). MDRO detection by (1) admission/discharge surveillance cultures or (2) clinical cultures were compared to daily surveillance cultures. Samples underwent 16S rRNA gene sequencing to measure the relative abundance of operational taxonomic units (OTUs) corresponding to each MDRO.

Results: Compared with daily surveillance cultures, admission/discharge cultures detected 91% of prevalent MDRO colonization and 63% of incident MDRO colonization among medical ICU patients. Only a minority (7%) of MDRO carriers were identified by clinical cultures. Higher relative abundance of MDRO-associated OTUs and specific antibiotic exposures were independently associated with higher probability of MDRO detection by culture.

Conclusion: Admission and discharge surveillance cultures underestimated MDRO acquisitions in an ICU. These limitations should be considered when designing sampling strategies for epidemiologic studies that use culture-based surveillance.

Keywords: antibiotic resistance; carbapenem resistance; colonization; extended-spectrum beta-lactamase; intensive care unit; microbiome; vancomycin-resistant enterococcus.