Risk factors for nosocomial methicillin resistant Staphylococcus aureus (MRSA) colonization in a neonatal intensive care unit: A Case-control study

To determine risk factors for MRSA colonization in a Level IV Neonatal Intensive Care Unit (NICU) independent of length of stay and gestational age in the context of a persistently circulating MRSA clone.Retrospective matched case-control study.Level IV NICU PATIENTS: Infants admitted between April 4,2017- March 31,2018.Based on weekly surveillance cultures, infants who acquired MRSA were matched 1:1 with MRSA-negative control infants by duration of exposure (length of stay) and gestational age to determine risk factors for acquisition.Fifty case infants were matched with controls. Isolates from 45 of the 50 cases were mupirocin-resistant and related by pulse-field gel electrophoresis. On matched univariable analysis, the following were significantly associated with a risk for MRSA acquisition: 1.Bed location in the acute area(P = 0.03), 2.Requirement of any level of respiratory support during the week prior to MRSA detection(P = 0.04), 3.Higher ATP pass rate (a measure of effectiveness of cleaning) during the week of and week prior(P = 0.01), 4.Higher MRSA colonization pressure during the week of and week prior(P0.0001), 5.Not having a hearing test during the time between the previous negative culture and MRSA acquisition(P = 0.01). A multivariable conditional logistic regression model (that excluded ATP pass rate) found that only colonization pressure was associated with acquisition of MRSA colonization.In an outbreak setting, MRSA colonization pressure is significantly associated with MRSA acquisition in the NICU independent of length of stay and gestational age.