Factors influencing the clinical outcome of methicillin-resistant Staphylococcus aureus bacteraemia

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia is associated with high mortality due to a combination of host, pathogen and therapy related factors. This was a retrospective exploratory study to evaluate host, pathogen and therapy related factors influencing the clinical outcome of MRSA bacteraemia in a UK teaching hospital setting. Of the 38 consecutive episodes of MRSA bacteraemia over a 1-year period, 16 of 38 (40%) patients died at 1 month and 21/38 (55%) died at 6 months. Univariate analysis revealed age (p < 0.006), mean serum vancomycin level (p < 0.035), agr group I (p < 0.036) and set4-var2_11 gene (p < 0.036) at 1 month; and age (p < 0.004) and set4-var2_11 gene (p < 0.002) at 6 months as significant factors. However, there was no association between first trough vancomycin concentration and outcome at 1 month. Multivariate survival analysis from time of admission showed, for each one year increase in age, a patient is 1.121 (95% CI 1.006-1.250, p < 0.007) times more likely to die at any particular point in time, and patients with a mean serum vancomycin level of <10 mg/L, the odds ratio of adverse outcome is 16.129 (95% CI 2.398-111.111) compared to patients with a mean serum level >10 mg/L. A variety of host, pathogen, and therapy related factors influence the clinical outcome of MRSA bacteraemia.

Treatment options for methicillin-resistant Staphylococcus aureus (MRSA) infection: Where are we now?

“…These data support the recent guidelines for vancomycin dosing [22] that recommend a trough serum concentration of !15 mg/L, supported by clinical data [48]. According to Monte Carlo simulation, this target is attainable only when the MIC of MRSA is 1 mg/L [23].…”

Predictors of Mortality in Staphylococcus aureus Bacteremia

“…These include pathogen-specific factors such as SCCmec-associated virulence factors (3), with SCCmec type II being an independent predictor of mortality in a cohort study of 253 SAB (64% MRSA) (77) and 744 SAB (33% MRSA) (33) episodes. Alternatively, differences in empirical prescribing (243) and poor vancomycin efficacy (3,86,114) may explain some of these differences. Compared to semisynthetic penicillins, vancomycin has slower bactericidal activity in vitro, especially with high-inoculum infections (158,252), and variable tissue penetration (2,88,157).…”

High vancomycin minimum inhibitory concentration is a predictor of mortality in meticillin-resistant Staphylococcus aureus bacteraemia

“…However, reduced susceptibility to vancomycin in S. aureus isolates has been a major medical concern for more than a decade [6][7][8][9][10][11][12][13]. A number of studies have reported that elevated vancomycin minimum inhibitory concentrations (MICs) in MRSA isolates are associated with significantly higher mortality in the treatment of MRSA bacteraemia [8][9][10].…”

“…A number of studies have reported that elevated vancomycin minimum inhibitory concentrations (MICs) in MRSA isolates are associated with significantly higher mortality in the treatment of MRSA bacteraemia [8][9][10]. However, several recent reports showed no significant influence of MIC on the treatment outcome of patients infected with high-MIC isolates [11][12][13].…”