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

Failure of vancomycin in the treatment of meticillin-resistant Staphylococcus aureus (MRSA) bacteraemia has been reported despite full susceptibility of the organism to vancomycin. A retrospective observational cohort study including 137 patients with MRSA bacteraemia was performed at two centres in South Korea during 2009-2010. A total of 137 patients with MRSA bacteraemia receiving vancomycin therapy were enrolled during the study period. Isolates from 13 (9.5%) of the 137 patients had minimum inhibitory concentrations (MICs) ≥1 μg/mL. The 30-day cumulative survival was 53.8% for patients infected with isolates having a MIC≥1 μg/mL and 79.8% for patients infected with isolates having a MIC<1 μg/mL (log-rank test, P=0.026). Vancomycin MIC≥1 μg/mL [hazard ratio (HR)=7.0, 95% confidence interval (CI) 2.2-22.1; P=0.001], nosocomial acquisition of bacteraemia (HR=5.4, 95% CI 1.4-20.1; P=0.013), rapidly fatal underlying diseases (HR=20.5, 95% CI 3.9-106.4; P<0.001), presentation with septic shock (HR=8.4, 95% CI 3.0-23.3; P<0.001), presence of complicated infections (HR=5.6, 95% CI 2.0-15.8; P=0.001) and persistent MRSA bacteraemia for ≥3 days (HR=4.2, 95% CI 1.4-12.7; P=0.012) were independent predictors of 30-day mortality in patients with MRSA bacteraemia. In patients with high Pitt bacteraemia scores (Pitt score ≥2), the delay in initiation of vancomycin therapy was significantly different between non-survivors and survivors (2.4 days vs. 1.1 days; P=0.012). Vancomycin MIC≥1 μg/mL had a significant impact on mortality of patients with MRSA bacteraemia. These findings support early consideration of alternative anti-MRSA agents in patients with MRSA bacteraemia who have high vancomycin MICs as well as prompt initiation of anti-MRSA treatment in patients with MRSA bacteraemia, especially those with high Pitt scores.

Wi YM ，Kim JM ，Joo EJ ，Ha YE ，Kang CI ，Ko KS ，Chung DR ，Song JH ，Peck KR ... -  《-》

Predicting high vancomycin minimum inhibitory concentration isolate infection among patients with community-onset methicillin-resistant Staphylococcus aureus bacteraemia.

Methicillin-resistant Staphylococcus aureus (MRSA) isolates with an elevated vancomycin MIC ≥2 mg/L have been increasingly identified in many countries. We aimed to develop a clinical score to predict vancomycin MIC ≥2 mg/L in patients with community-onset MRSA bacteraemia. This retrospective cohort study enrolled 394 patients with MRSA bacteraemia. Vancomycin MICs of all MRSA isolates were determined by agar dilution method. Clinical characteristics between patients with high (≥2 mg/L) and low (≤1 mg/L) vancomycin MIC MRSA bacteraemia were compared. Independent predictors of high vancomycin MIC isolate infection were identified and used to create a score-based predictive model. Among the 394 study patients, 56 (14.2%) had MRSA isolates with a vancomycin MIC ≥2 mg/L. The final regression model included 6 independent predictors: chronic liver disease (adjusted odds ratio [aOR], 2.99; 95% confidence interval [CI], 1.39-6.42), prior recovery of MRSA from respiratory tract specimen (aOR, 2.54; 95% CI, 1.15-5.61), end-stage renal disease (aOR, 2.53; 95% CI, 1.33-4.78), severe sepsis or septic shock on presentation (aOR, 2.39; 95% CI, 1.28-4.44), prior vancomycin exposure (aOR, 2.21; 95% CI, 1.13-4.30), and recent hospitalization within 3 months (aOR, 2.11; 95% CI; 1.01-4.40). All independent predictors had a value of one point. Youden's index statistics indicated a score of ≥3 as best cutoff value that had a sensitivity of 69.6% and specificity of 78.4%. Simple decision rule helps clinicians stratify the risk of high vancomycin MIC MRSA infection when deciding empirical therapy for patients with community-onset infections.

Chen SY ，Hsueh PR ，Chiang WC ，Huang EP ，Lin CF ，Chang CH ，Chen SC ，Chen WJ ，Chang SC ，Lai MS ，Chie WC ... -  《-》

High vancomycin minimum inhibitory concentrations with heteroresistant vancomycin-intermediate Staphylococcus aureus in meticillin-resistant S. aureus bacteraemia patients.

Patients with high vancomycin minimum inhibitory concentrations (MICs) and heteroresistant vancomycin-intermediate Staphylococcus aureus (hVISA) infection are associated with treatment failure and poor outcomes. The main purpose of this study was to investigate the effect of hVISA on patient outcome, considering both the high vancomycin MIC and the existence of heteroresistant phenotypes. From January 2005 to December 2009, consecutive meticillin-resistant S. aureus (MRSA) isolates from 284 cases of MRSA bacteraemia receiving glycopeptide therapy were collected for further MIC and hVISA testing. The demographic distribution, clinical features and outcomes in bacteraemia patients with different vancomycin MICs and hVISA status in MRSA isolates were subsequently compared. Subjects were divided into three groups: low vancomycin MIC (<1.5mg/L) with vancomycin-sensitive S. aureus (VSSA) (n=50); high vancomycin MIC (≥1.5mg/L) with VSSA (n=218); and high vancomycin MIC with hVISA (n=16). Cox regression analysis demonstrated that the high MIC with VSSA group exhibited significantly higher 30-day mortality than the low MIC with VSSA group [odds ratio (OR)=2.349, 95% confidence interval (CI) 1.078-5.118]. The high MIC with hVISA phenotype was not associated with higher mortality but was independently associated with persistent MRSA bacteraemia (OR=5.996, 95% CI 1.438-25.005). To summarise, although hVISA is correlated with persistent bacteraemia, higher mortality in high vancomycin MIC infections could not be explained by the existing hVISA phenotype. Facing persistent bacteraemia under glycopeptide therapy for 7 days, clinicians should consider shifting to an alternative class of antibiotics to treat hVISA infection.

Wang JL ，Lai CH ，Lin HH ，Chen WF ，Shih YC ，Hung CH ... -  《-》

Risk factors for mortality in patients with persistent methicillin-resistant Staphylococcus aureus bacteraemia in a tertiary care hospital in Taiwan.

Lin SH ，Liao WH ，Lai CC ，Liao CH ，Tan CK ，Wang CY ，Huang YT ，Hsueh PR ... -  《-》

Methicillin-resistant Staphylococcus aureus bacteremia in hemodialysis and nondialysis patients.

Increased mortality has been reported in patients treated with vancomycin for methicillin-resistant Staphylococcus aureus (MRSA) bacteremia with high minimum inhibitory concentration (MIC) values within the susceptibility range. However, this finding has not been verified in hemodialysis patients, who have much higher invasive MRSA infection rates than nondialysis patients. We aimed at comparing vancomycin MICs between hemodialysis and nondialysis patients, and identifying predictors of high vancomycin MICs and infection-related mortality in hemodialysis patients with MRSA bacteremia. Patients with MRSA bacteremia from January 2008 through December 2009 were enrolled. Vancomycin MIC was determined for each first isolate using the Etest method. Clinical characteristics and vancomycin MICs were compared between hemodialysis and nondialysis patients. Factors associated with high vancomycin MIC (2 μg/mL) and infection-related mortality in hemodialysis patients were analyzed. A total of 162 MRSA bacteremia episodes were identified. Forty-four (27.0%) isolates were obtained from hemodialysis patients and 118 (73.0%) from nondialysis patients. Diabetes (63.3% vs. 39.8%, p = 0.007) and prior vancomycin exposure in 30 days (31.8% vs. 12.7%, p = 0.005) were more prevalent in hemodialysis group than in nondialysis group. A higher prevalence of vancomycin MIC of 2 μg/mL was observed in hemodialysis group in comparison with nondialysis group (11.4% vs. 1.7%, p = 0.016). In following analyses of hemodialysis group, patients with initial presentation of septic shock had a higher risk of vancomycin MIC of 2 μg/mL than nonseptic shock patients (100.0% vs. 38.5% p = 0.014). Infection-related mortality was associated with age, Acute Physiology and Chronic Health Evaluation II (APACHE-II) score >15, presence of septic shock, receipt of mechanical ventilation, and failure to remove source of bacteremia in univariate analysis. Hemodialysis patients with MRSA bacteremia are more likely to have a high vancomycin MIC (2 μg/mL) compared with nondialysis patients. Infection-related mortality is associated with the patient's clinical manifestations, including age, APACHE-II score >15, presence of septic shock, receipt of mechanical ventilation, and failure to remove source of bacteremia. Treatment selection should be tailored according to the patient's clinical condition.

Kan LP ，Lin JC ，Chiu SK ，Yeh YC ，Lin TY ，Yang YS ，Wang YC ，Wang NC ，Yeh KM ，Chang FY ... -  《-》