Vancomycin minimum inhibitory concentration, host comorbidities and mortality in Staphylococcus aureus bacteraemia

Area of Science:

• Infectious Diseases
• Clinical Microbiology
• Pharmacology

Background:

• Staphylococcus aureus bacteraemia (SAB) poses a significant mortality risk.
• Vancomycin is a critical antibiotic for treating SAB, but rising Minimum Inhibitory Concentrations (MICs) are a concern.
• Previous studies suggest a link between vancomycin MIC and patient outcomes, but the influence of clinical factors requires further investigation.

Purpose of the Study:

• To investigate the association between elevated vancomycin MIC and 30-day mortality in patients with SAB.
• To determine if clinical parameters like comorbidities and disease severity influence this association.
• To explore the persistence of the association in specific patient subgroups, including those with methicillin-susceptible S. aureus (MSSA) treated with flucloxacillin.

Main Methods:

• Retrospective analysis of a cohort of patients with SAB.
• Multivariable logistic regression analysis to assess the association between vancomycin MIC and 30-day mortality, adjusting for clinical factors.
• Subgroup analysis including patients with MSSA treated with flucloxacillin.

Main Results:

• An association between elevated vancomycin MIC and 30-day mortality in SAB was confirmed (p < 0.001).
• This association remained statistically significant after adjusting for comorbidities and disease severity scores.
• The association persisted in the subgroup of patients with MSSA bacteraemia treated with flucloxacillin.

Conclusions:

• Elevated vancomycin MIC is independently associated with increased 30-day mortality in patients with SAB.
• The findings suggest that the elevated MIC is linked to an organism factor contributing to mortality, rather than being directly causal.
• Further research into the specific organism factors influencing vancomycin MIC and patient outcomes is warranted.