Trending and modeling multi-drug resistant organisms in the Neonatal Intensive Care Unit
Jennifer Duchon, MD, MPH
BACKGROUND: Safe and effective antimicrobial therapy for neonates infected with multidrug resistant organisms (MDROs) is limited so both active and passive surveillance for MDROs are important interventions to prevent transmission and infection with MDROs in neonates hospitalized in the Neonatal Intensive Care Unit (NICU). Surveillance data analyzed from infants transferred to the 2 NICUs affiliated with New York Presbyterian (NYP) demonstrated low rates of MDRO colonization in the first week of life. Thus, we changed our surveillance policy to only culture infants 7 days of age and older, providing us with a unique opportunity to assess these different surveillance strategies and monitor the safety of this change
GAP: Optimal strategies, risks, costs, and benefits of surveillance in the NICU population have not been fully evaluated
1) Colonization of transferred infants >7 days old with MDROs will be similar before and after surveillance policy change.
2) Infections with MDROs among all infants will be similar before and after surveillance policy change.
3) Predictive models can estimate colonization of all infants in the NICU and further refine targeted MDRO surveillance by predicting potential outbreak conditions.
METHODS: Eligible subjects are all infants hospitalized in the NICUs of NYP from July 2007-June 2016. The rates of MDRO colonization and infection from July 2007-June 2013 when all transferred infants had surveillance cultures performed with rates from July 2013-July 2016, when only infants >7 days old had surveillance cultures performed will be assessed, and predictive models of MDRO colonization and transmission will be hypothesized using Bayesian algorithms.
Hypothesis 1: From 2007-2016, 2925 infants were transferred to the NYP NICUs, 1101 at Site 1 and 1824 at Site 2; 2571 (88%) had surveillance for at least 1 ARO. There were 226 positive surveillance cultures in 204 infants (8%): 94 (3.7%) for MRSA, 78 (3%) for VRE and 54 (2%) for MDR-GNR. Site 1 elected not to adopt the change in surveillance policy. In the final models, transfer DOL remained a highly significant (OR per day = 1.018, CI95 1.014, 1.022, p< 0.001) predictor of colonization with any ARO. There was no significant increase in the incidence of colonized infants over time; this remained true in infants who were < 7 days of life at Site 1. There was a trend towards increased incidence of infants colonized with MDR-GNR over time.
Hypothesis 2: From 2007-2016, 16467 infants were admitted to the NYP NICUs and included in the analysis, 7198 at Site 1 and 9269 at Site 2; There were 380 positive clinical cultures during that time period (2.3%): 105 (0.6%) for MRSA, 13 (0.1%) for VRE and 262 (1.6%) for MDR-GNR.
In the final models, there was a 1.036 increased risk of any ARO infection post-policy change (CI 95 1.014, 1.059; p<=0.0011). This change was primarily in infants with a birth weight of < 750 grams (RR 1.18, CI 95 = 1.03, 1.36; p = 0.017), and driven by MDR-GNR.
Exploratory Aim 3: An agent based model was parameterized based as suxh: Among infants, individual health states included: susceptible to colonization/infection, colonized, or infected with an ARO. HCWs could be susceptible to colonization/infection or colonized with an ARO. We tested two colonization probabilities: 17/1000 admissions, representing the actual historical colonization rate with any ARO from 2004-2010 in infants transported at < 7 days of life vs 65/1000 admissions, representing a "worst case scenario," the colonization rate of any ARO in all transferred infants in 2010.
In 100 simulations designed to occur over a 3 month period, where 17/1000 infants were colonized, 9 simulations resulted in successful secondary transmission and 1 simulation resulted in an infected infant. By comparison, in 100 simulations where 65/1000 infants were colonized, 12 simulations resulted in secondary transmission, and 3 included an infected infant.
IMPACT: This project may inform surveillance guidelines for the NICU population; future research can test the generalizability of these guidelines beyond our NICUs, with an ultimate goal of providing a means to prevent transmission and infection with MDROs in the NICU.