(diversity index 0.9773). Twenty eight (26.9%) isolates belonged to 14 (31.1%) spa types that were only observed in the environment. The most prevalent spa types were t084 (N=10, 9.6%), t026 (N=8, 7.7%), t091 (n=7, 6.7%), and t7384 (N=7, 6.7%) (Supplementary file 3). When multiple locations (n=45) in one room were simultaneously positive, the isolates were of the same spa type, with three (6.7%) exceptions (Figure 4). In all cases when positive cultures were taken from the same site over time, isolates were of different spa types, indicating no long-term contamination (Figure 4). No surfaces positive at both sampling moments were identified in the old hospital building. Figure 4. Spa types found over time in rooms that were positive at more than one sampling moment. Spa types observed at different moments or in different rooms are colored, spa types observed at only one moment in one room are grey. Darker grey was used to indicate that two spa types were identified at one moment, but in the same room. Node sizes are relative to the number of MSSA strains found. Abbreviations: SR single-occupancy room, IR Isolation room, ICU Intensive Care Unit. Epidemiological link between clinical strains and environmental strains Of the 468 typed isolates from patients with an epidemiological link to the ward of a positive room, 16 (3.4%) isolates of 16 patients were of the same spa type as the environmental MSSA isolate. For eight patients (50.0%), the clinical sample was taken before the environmental sample was taken (3 to 62 days earlier), for eight (50.0%) patients, cultures were taken after environmental sampling (7 to 75 days after). Seven patients were admitted to a room that was found to be contaminated by environmental sampling; four (25.0%) 106 Chapter 2.4
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