204 - Simplifying Surveillance Sampling: Can Environmental Surveillance Replace Perianal Screening?

Background: While active surveillance for multidrug-resistant organism (MDRO) colonization permits timely intervention, obtaining cultures can be time-consuming, costly, and uncomfortable for patients. We evaluated whether there are clinical differences between patients with and without attainable perianal cultures and whether environmental surveillance could replace perianal screening.

Methods: We collected active surveillance cultures from patient hands, nares, groin, and perianal area upon enrollment, at day 14, and monthly thereafter in six Michigan nursing homes. Methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), and resistant gram-negative bacilli (RGNB) were identified using standard methods. Patient characteristics were collected by trained research professionals.
This sub-study focuses on visits where all body sites were collected. To determine the contribution of perianal screening to MDRO detection, site of colonization was categorized into two groups: perianal and non-perianal. We evaluated the utility of multi-site surveillance (e.g. type I & type II error) using non-perianal sites and environment surveillance. To evaluate characteristics associated with the acquisition of perianal cultures (e.g. selection bias), we compared clinical characteristics, patient colonization, and room environment contamination of patients where all body sites were collected (533 patients; 1026 visits) to patients with all body sites except the perianal culture (108 patients; 168 visits).

Results: Of 651 patients, 533 met the inclusion criteria; average age 74.5 years, 42.6% male, and 60.8% white. Of 1026 eligible visits, 620 visits detected MDRO colonized patients; 155 MRSA, 363 VRE, and 386 RGNB (Table 1). If perianal cultures weren’t collected, non-perianal surveillance misses 7.7%, 41.3%, and 45.1% of MRSA, VRE, and RGNB colonized visits, respectively. The addition of environmental surveillance to non-perianal screening detected 95.5%, 82.9%, and 67.9% of MRSA, VRE, and RGNB colonized visits, respectively. The specificity of environmental screening was 85.3%, 72.7%, and 73.4% for MRSA, VRE, and RGNB, respectively.
Patients without attainable perianal cultures had significantly lower cognitive function, more comorbidities, worse functional status, longer length of stay, and higher baseline presence of wounds than patients with attainable perianal cultures; introducing potential selection bias to surveillance efforts (Table 2). No significant differences in patient colonization and room contamination were noted between patients with and without attainable perianal cultures.

Conclusion: Perianal screening is important for the detection of VRE and RGNB colonization. Infection prevention must be cognizant of the tradeoff between reducing type II error and the selection bias that occurs with required attainment of perianal cultures. In the absence of perianal cultures, environmental surveillance improves MDRO detection whilst introducing type I error.