A new study is shedding light on how bioburden and patient colonization play off each other.
As we work towards making health care safer and establishing a stronger role for infection control in patient care, the role of bioburden and environmental contamination is a common conversation topic. The US Centers for Disease Control and Prevention (CDC) recently reported that each year roughly 2.8 million Americans are infected with antibiotic-resistant infections, which result in 35,000 associated deaths. Organisms like vancomycin-resistant Enterococci (VRE), drug-resistant Candida, Methicillin-resistant Staphylococcus aureus, are all considered serious threats in the CDC’s 2019 Antibiotic Resistance Threats Report.
One conversation that we consistently have in infection prevention is about isolation and screening of patients with multidrug-resistant organisms (MDROs) and/or Clostridioides difficile. What is the role of patients without active infection who are likely just colonized in transmission? Will they shed such organisms and contaminate their environmental surroundings? Such issues are all things that impact isolation and environmental cleaning in health care settings. With this in mind, investigators of a new study, published in Open Forum Infectious Diseases, sought to understand the relationship between environmental contamination and patient colonization with VRE and whether it impacted negative health outcomes.
To assess this relationship, investigators studied 463 patients in post-acute care in Ann Arbor, Michigan. The patients were assessed from point of enrollment through discharge and then for 6 months. Body and environmental samples were taken at specific temporal intervals to determine patient colonization and environmental contamination, as well as the dynamics of long stays, unplanned hospitalization, and infections which were adjusted for sex/age/race, Charlson’s Comorbidity Index, and physical self-maintenance.
Understanding the relationship dynamics between patient colonization and environmental contamination for MDROs such as VRE is critical. Not only does it help us to appreciate the transmission dynamics but also alerts us if screening is necessary. Following their analysis, the investigators of this study found that new infection or acquisition of VRE was more likely in patients in contaminated rooms (Odds ratio [OR]: 3.75). The opposite of this relationship was also found; contamination of a room was more likely when the patient had VRE. While this relationship isn’t surprising, it emphasizes the importance of daily environmental cleaning and rapid isolation for those with known VRE infections or colonization.
For those patients or rooms with new VRE acquisition, researchers found that increased length of stay played a critical role (new acquisition OR: of 4.36; new contamination OR: 4.61).
Moreover, contaminated rooms increase the risk for colonization, and both are associated with future adverse health outcomes. New infections were more common in those areas with higher VRE burdens. The authors cite the figures, “15% in the absence of VRE, 20% when following VRE isolation only on the patient or only in the room, and 29% following VRE isolation in both the patient and the room”.
Overall in this study, patients who acquired VRE and became infected with the organism, tended to stay in rooms with VRE contamination. As colonization can increase the risk for future adverse events, the authors emphasized the importance of screening for MDROs on admission.
From the infection prevention perspective, this reinforces the push to screen patients, even if just in high-risk areas like intensive care and oncology units. This study sheds light on the role of environmental contamination in increasing risk of VRE acquisition by patients and how those patients with VRE can easily contaminate their space.
It is well established that as length of stay increases, so does the risk for infection, so this study further reinforces this point. The symbiotic relationship between environmental contamination and patient colonization or infection is a lesson we must truly listen to and apply to infection control efforts. More prevalent environmental disinfection, screening, and stringent patient isolation are all steps we can take to break the chain of infection.