183 Clinical sub-phenotypes of Staphylococcus aureus bacteraemia 8 had higher 84-day mortality. Patients assigned to sub-phenotype B had the lowest mortality and lowest rate of persistent bacteraemia. Persistent bacteraemia at day 7 was uncommon but mostly occurred in sub-phenotype C. Secondary analysis of the effect of adjunctive rifampicin treatment stratified by SAB sub-phenotype An application of stratification of patients with SAB into sub-phenotypes is to enrich clinical trial design. Within the ARREST cohort, we considered each sub-phenotype separately and within each compared the effect of adjunctive rifampicin on 84-day mortality and composite microbiologic failure (Figure 3; Supplementary Table 2). Patients assigned to sub-phenotype B and randomised to adjunctive rifampicin had a higher 84-day mortality rate compared to patients randomised to placebo (odds ratio (OR) 18·8, 95% confidence interval (CI) 1·1–334·4, p=0·006). In sub-phenotype C, randomisation to adjunctive rifampicin was associated with reduced composite microbiologic failure (OR 0·17, 95% CI 0·04–0·8, p=0·02). A B C D E -2 -1 0 1 2 Sub-phenotype Z-score Edinburgh cohort (p<0.0001) ARREST placebo arm (p<0.0001) A B C D E -2 -1 0 1 2 Sub-phenotype p=0.04 84-day mortality Persistence or recurrence A B C D E -2 -1 0 1 2 Sub-phenotype p=0.08 Edinburgh cohort ARREST placebo arm A B C Composite microbiologic failure Figure 2: Comparison of outcomes between SAB sub-phenotypesComparison of (A) all-cause 84-day mortality, (B) persistent or recurrent bacteraemia in the Edinburgh retrospective observational cohort, and (C) composite microbiologic failure in the ARREST trial placebo arm. Bars represent z-scores comparing the outcome between sub-phenotypes within the same cohort. Differences in the proportion of patients with each outcome between sub-phenotypes were compared using Fisher’s Exact test or Chi-squared test.
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