Clinical samples MSSA Five hundred MSSA isolates from clinical samples from 487 patients were available for spa typing (Figure 3). Most isolates were identified from the nose (n=118), sputum (n=103) or blood (n=50). Thirty-two isolates (6.4%) were identified before or during hospitalization from patients included in the MOVE-study (Figure 2b). Four-hundred and sixty-eight (93.4%) isolates from 418 patients were included due to an epidemiological link with a contaminated room. Two hundred and fifteen different spa types were detected, 159 (74.0%) types were observed once (diversity index 0.9799). The most prevalent spa types were t084 (N=36, 7.2%), t091 (N=31, 6.2%), and t571 (N=28, 5.6%) (Supplementary file 3). MRSA Two MRSA isolates were identified from patients included in the MOVE study. The two isolates belonged to spa type t304 and t002 (Figure 3, Supplementary file 3). As no MRSA was found in the environment, per definition no epidemiological link with a patient could be established. Nasal samples compared to clinical samples Twenty-eight (4.2%) out of 673 patients had clinical samples positive for S. aureus taken before or during their hospitalization, 26 patients were MSSA positive, one patient MRSA positive, and one patient was MSSA and MRSA positive (Figure 2b). For the MRSA positive patient, the clinical sample was taken during hospitalization. This patient was also positive for MRSA upon admission to the hospital, both isolates belonged to spa t304. From the 27 MSSA positive patients, 32 MSSA isolates were cultured. For 22 clinical isolates, belonging to 22 patients, the clinical isolate was identical to the admission or discharge isolate. For 16 (72.7%) isolates the sample was taken during hospitalization, for six (27.3%) isolates the sample was taken <1 year before hospitalization. For ten (31.3%) isolates from eight patients, the clinical isolate was not identical to the admission or discharge nasal isolate. Of these ten, three (30.0%) isolates were identified from a clinical sample taken during the hospitalization, for two (20.0%) this was <1 year before hospitalization and for five (50.0%) this was >1 year before hospitalization. By definition, three of the 19 (15.9%) isolates identified in clinical cultures during the hospitalization had an exogenous source. Presence of S. aureus in the environment In total, 4,993 environmental samples were taken, 724 (14.5%) in the old and 4,269 (85.5%) in the new hospital building. No MRSA was detected, MSSA was found on 22/724 (3.0%) surfaces in the old building, compared to 120/4269 (2.8%) surfaces in the new building (P=0.733) (Supplementary file 4). One hundred and forty-five MSSA isolates were identified on 142 surfaces, 104 isolates were available for spa typing, all from the new hospital building. Forty-five different spa types were detected, 24 (54.5%) were observed once 2 105 Dynamics of S. aureus in patients and the hospital environment
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