Association of methicillin resistance with mortality of hospital-acquired Staphylococcus aureus bacteremia

Objective Methicillin-resistant (MR) Staphylococcus aureus bacteremia (SAB) is associated with higher mortality rates than methicillin-susceptible (MS) SAB. This study assessed potential predictors of mortality and evaluated the association of methicillin resistance with mortality in patients with SAB. Methods We conducted a retrospective cohort study in patients with hospital-acquired SAB, from 2009 to 2018. Clinical features of patients with MR-SAB were compared with those of patients with MS-SAB and predictors of 30-day mortality were determined using Cox regression analysis. Results Among 162 patients, 56.8% had MR-SAB. Overall 30-day mortality was 19.1%; MR-SAB had higher mortality (25.0%) than MS-SAB (11.4%). Univariate analysis highlighted long-term hospitalization, prior antibiotics use, and delayed initiation of appropriate antibiotics as risk factors. Cox regression analysis showed that respiratory tract source, Pitt bacteremia score, Charlson comorbidity index, and appropriate antibiotic therapy within 24 hours were independently and significantly associated with 30-day mortality outcome. Conclusions Methicillin resistance was not an independent risk factor for mortality in patients with SAB. Early, appropriate antibiotic treatment is an important prognostic factor.