Nosocomial Methicillin-resistant Staphylococcus aureus: Acquisition, Infection and Decolonization

Methicillin-resistant Staphylococcus aureus (MRSA), an antibiotic-resistant bacteria, is often carried asymptomatically, but can cause severe disease. In this thesis, I present three retrospective cohort studies conducted in Toronto, Canada, which examine risk factors for infection or acquisition. In a study of 1,125 adult MRSA carriers at a tertiary hospital, risk factors for subsequent MRSA-positive clinically-indicated specimens were recent identification of carriage, older age, male gender, nosocomial acquisition, carriage detection in ICU, and underlying liver conditions. In a study of pairs of patients at two hospitals who shared a room for ≥48 hours, each pair included a MRSA-index case and a patient at risk of acquisition. Fluoroquinolone receipt by either patient increased the probability of MRSA transmission. Nearly half of identified acquisitions in the year following shared occupancy were unrelated to the MRSA-index case. In a study of 62,552 patient admissions, receipt of fluoroquinolone(s) and exposure to high MRSA colonization pressure in the prior week were significant risk factors for MRSA acquisition. The results of the cohort studies suggest that MRSA control should involve consideration of antibiotic exposures among those colonized and those at risk of acquisition. Antimicrobial stewardship and interventions that identify carriers could reduce disease burden.Ph.D.2020-11-19 00:00:0