It is well known that bacteremia caused by Staphylococcus aureus is characterized by a high frequency of death. At the same time, the clinical significance of resistance to methicillin S.aureus in bacteremia is currently a controversial subject. This is in part due to the difficulties in conducting comparative clinical studies of the results of bacteremia caused by methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive strains (MSSA), which in turn is due to the severity disease variable.

In this regard, a group of Belgian researchers conducted a retrospective cohort analysis and 2 independent case-control studies, the aim of which was to compare the results and the mortality in patients with severe bacteremia caused by MSSA (n = 38). and MRSA (n = 47). For case-control studies, the selection of comparison pairs (1: 2 ratio) was carried out on the basis of diagnostic criteria for bacteremia and an APACHE II score.

It was found that patients with MRSA-induced bacteremia, more often than patients with MSSA-induced bacteremia, developed acute renal failure (ARF) and hemodynamic failure. Patients in the first group required longer mechanical ventilation (VLT) and had a longer stay in the intensive care unit. Compared to patients with MSSA-induced bacteremia, they had a higher 30-day mortality rate (53.2% vs 18.4%) and a higher hospital mortality rate (63.8% vs 23.7%) (p less than 0.05).

Multiple analyzes have revealed factors such as the presence of acute renal failure, the duration of mechanical ventilation, age and methicillin resistance of S. aureus as independent predictors of death (p less than 0.05). The attributable mortality in the group of patients with bacteremia caused by MSSA was 1.3% (23.7% and 22.4% in the study and control groups, respectively, p = 0.94). The attributable mortality in the group of patients with MRSA-induced bacteremia was significantly higher and amounted to 23.4% (63.8% and 40.4% in the study and control groups, respectively, p = 0.02). Statistical analysis confirmed the magnitude of the difference (22.1%) between attributable mortality in patients with bacteremia caused by MRSA and MSSA (95% confidence interval 8.8% -35.3% ).

Thus, the researchers confirmed that resistance to methicillin in S.aureus is associated with higher attributable mortality in patients with bacteremia.