Impact of Vancomycin MIC on Treatment Outcomes in Invasive Staphylococcus aureus Infections

Abstract

There are conflicting data on the association of vancomycin MIC (VAN-MIC) with treatment outcomes in Staphylococcus aureus infections. We investigated the relationship between high VAN-MIC and 30-day mortality and identified the risk factors for mortality in a large cohort of patients with invasive S. aureus (ISA) infections, defined as the isolation of S. aureus from a normally sterile site. Over a 2-year period, 1,027 adult patients with ISA infections were enrolled in 10 hospitals, including 673 (66%) patients with methicillin-resistant S. aureus (MRSA) infections. There were 200 (19.5%) isolates with high VAN-MIC (Ն1.5 mg/liter) by Etest and 87 (8.5%) by broth microdilution (BMD). The all-cause 30-day mortality rate was 27.4%. High VAN-MIC by either method was not associated with all-cause 30-day mortality, and this finding was consistent across MIC methodologies and methicillin susceptibilities. We conclude that high VAN-MIC is not associated with increased risk of all-cause 30-day mortality in ISA infections. Our data support the view that VAN-MIC alone is not sufficient evidence to change current clinical practice.

Discordance of vancomycin minimum inhibitory concentration for methicillin-resistant Staphylococcus aureus at 2 μg/mL between Vitek II, E-test, and Broth Microdilution

“…Although previous studies have stated that E-tests over estimated high vancomycin MICs and Vitek II might fail to detect vancomycin MIC elevation (Swenson et al, 2009;Bloomgren & Laible, 2013;Tomczak et al, 2013), our results revealed that the E-test derived MICs were highly consistent with those provided by broth microdilution. This finding is in line with recent studies (Van Hal et al, 2011;Song et al, 2017). Likewise, Hsu et al (2008) suggested that MICs derived by E-tests were more reflective of the prognosis.…”

“…The literature contains conflicting data regarding whether MRSA-vancomycin MICs could actually reflect the prognosis. Some studies have suggested that vancomycin MICs enabled the determination of adverse clinical outcomes (Honda et al, 2011;Han et al, 2012;Rojas et al, 2012;Hope et al, 2013), whereas others have not (Hos et al, 2017;Song et al, 2017;Adani et al, 2018;Bouiller et al, 2018). Because the MIC-guided treatment decision is controversial in low MRSA-vancomycin MICs (≤2 µg/mL), the IDSA also recommends that the actual clinical and microbiological response should be considered as a guide to treatment decisions if the MRSA-vancomycin MIC is low (Liu et al, 2011).…”

Genomic insights on heterogeneous resistance to vancomycin and teicoplanin in Methicillin-resistant Staphylococcus aureus: A first report from South India

“…A higher vancomycin and teicoplanin MIC of ≥ 1.5 μg/ml has been linked to poor clinical outcomes in patients with MRSA bacteremia [5–7]. In recent years, heterogeneous vancomycin-intermediate S .…”

Epidemiology of Methicillin-Resistant Staphylococcus Aureus Bloodstream Infections from 2013-2017 at Chiang Mai University: What Changes Occurred from 2007-2011?

“…There are con icting data with regard to the association between treatment failure and an MIC of 1.5 mg/L or greater. [18,19,31,32] This study demonstrated no association between mortality and an MIC of 1.5 mg/L or greater. Given a vancomycin MIC of ≤ 1.5 mg/L, vancomycin is still a mainstay of treatment for MRSA infection in our hospital.…”