Prevalence and Clinical Impact of Heterogeneous Vancomycin-Intermediate Staphylococcus aureus Isolated From Hospitalized Patients

Abstract

BackgroundWe estimated the prevalence and clinical impact of heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA). The concordance between macromethod and glycopeptide resistance detection (GRD) E tests was determined. In addition, predictors of clinical outcomes in hospitalized patients with S. aureus bacteremia (SAB) or pneumonia (SAP) were evaluated.MethodsWe obtained 229 consecutive S. aureus isolates from all hospitalized patients at two university hospitals located in Busan and Yangsan, Korea. Standard, macromethod, and GRD E tests were performed. Additionally, we reviewed the medical records of all patients. Among the 229 patients, predictors of clinical outcomes were analyzed for 107 patients with SAB and 39 with SAP.ResultsAmong the 229 isolates, 34.5% of S. aureus isolates and 50.7% of methicillin-resistant S. aureus isolates exhibited the hVISA phenotype based on the macromethod E test. hVISA was nearly associated with treatment failure in patients with SAB (P=0.054) and was significantly associated with treatment failure in patients with SAP (P=0.014). However, hVISA was not associated with 30-day mortality in patients with SAB or SAP. The concordance between the macromethod and GRD E tests was 84.2%.ConclusionshVISA is quite common in the southeastern part of Korea. hVISA is associated with treatment failure in patients with SAP.

Recent pattern of antibiotic resistance in Staphylococcus aureus clinical isolates in Eastern India and the emergence of reduced susceptibility to vancomycin

“…As regards vancomycin susceptibility, hVISA was first reported in Japan in 1997 and along with VISA has since been identified worldwide from many countries including the United States, Japan, Australia, France, Scotland, Brazil, South Korea, Hong Kong, South Africa, Thailand, Israel, and others. [3,4] In India, Menezes et al [15] in 2008 reported the emergence of vancomycin-intermediate Staphylococcus species in Southern India using the revised guidelines. Of 102 oxacillin-resistant S. aureus isolates, one was found to be a VISA strain (MIC 5 µg/ml).…”

“…[1,2] For MRSA and multidrug-resistant (MDR) S. aureus infections, vancomycin is considered the mainstay of antimicrobial therapy and has been the treatment of choice for serious MRSA infections since 1958. [3] However, emerging reports of vancomycin minimum inhibitory concentrations (MIC) creep, reduced vancomycin susceptibility (RVS), and even vancomycin resistance in clinical MRSA isolates from different geographical regions are disturbing, because of minimal alternative therapeutic options. [3][4][5][6] This is because the clinical effectiveness of vancomycin may be compromised even against vancomycin-sensitive S. aureus (VSSA) strains whose MICs are within the Clinical and Laboratory Standards Institute (CLSI) susceptible range (≤2 µg/ml).…”

“…[3] However, emerging reports of vancomycin minimum inhibitory concentrations (MIC) creep, reduced vancomycin susceptibility (RVS), and even vancomycin resistance in clinical MRSA isolates from different geographical regions are disturbing, because of minimal alternative therapeutic options. [3][4][5][6] This is because the clinical effectiveness of vancomycin may be compromised even against vancomycin-sensitive S. aureus (VSSA) strains whose MICs are within the Clinical and Laboratory Standards Institute (CLSI) susceptible range (≤2 µg/ml). Such heterogeneous vancomycin-intermediate S. aureus (hVISA) strains may evolve into VISA, leading to clinical treatment failure.…”

“…Such heterogeneous vancomycin-intermediate S. aureus (hVISA) strains may evolve into VISA, leading to clinical treatment failure. [3,4] Recently, it has also been observed that high vancomycin MIC in methicillin-susceptible S. aureus (MSSA) is associated with poorer outcomes and increased complications in patients with S. aureus bacteremia and endocarditis. [7,8] Thus, determination of vancomycin MIC and the ability to accurately identify S. aureus isolates with reduced susceptibility to vancomycin is of paramount importance for several reasons such as successful clinical outcomes, the targeted treatment of MRSA bacteremia, or as a prognostic marker in MSSA bacteremia.…”

Comparison of E test GRD and vancomycin screen agar (BHI-V3 and BHI-V4) in detection of heteroresistant vancomycin intermediate staphylococcus aureus (hVISA).

“…14 Studies that followed, confirmed the high specificity of E test GRD ranging from 85.8% to 97% but lower sensitivity levels ranging from 57% to 82%. 15,16 Presently, most of the studies recommend using two different methods for more accurate detection of VISA/hVISA strains (CDC).…”