A Dysregulated Balance of Proinflammatory and Anti-Inflammatory Host Cytokine Response Early During Therapy Predicts Persistence and Mortality in Staphylococcus aureus Bacteremia.

OBJECTIVES: The contribution of individual immune response to Staphylococcus aureus bacteremia on outcome has not been well studied. The objective was to relate the host cytokine response to outcome of Staphylococcus aureus bacteremia. DESIGN: Prospective observational study. SETTING: Three U.S. university-affiliated medical centers. PATIENTS: Adult patients infected with Staphylococcus aureus bacteremia hospitalized between July 2012 and August 2014. INTERVENTIONS: Blood specimens were obtained at Staphylococcus aureus bacteremia onset and 72 hours after therapy initiation. Levels of tissue necrosis factor, interleukin-6, interleukin-8, interleukin-17A, and interleukin-10 were measured by enzyme-linked immunosorbent assay at each time point and compared between those with persistent bacteremia (≥ 4 d) and resolving bacteremia. Primary outcome was persistent bacteremia after 4 days of effective therapy. Secondary outcomes were 30-day mortality and 30-day recurrence. MEASUREMENTS AND MAIN RESULTS: A total of 196 patients were included (mean age, 59 yr); of them, 33% had methicillin-resistant Staphylococcus aureus bacteremia. Forty-seven percent of the methicillin-resistant Staphylococcus aureus strains were staphylococcal cassette chromosome mec IV. Persistent bacteremia occurred in 24% of patients (47/196); they were more likely to die than resolving bacteremia group (28% vs 5%; p < 0.001). Compared with resolving bacteremia group, persistent bacteremia patients had higher initial median levels of tissue necrosis factor (44.73 vs 21.68 pg/mL; p < 0.001), interleukin-8 (124.76 vs 47.48 pg/mL; p = 0.028), and interleukin-10 (104.31 vs 29.72 pg/mL; p < 0.001). Despite 72 hours of treatment, levels remained higher for the persistent bacteremia group than for the resolving bacteremia group (tissue necrosis factor: 26.95 vs 18.38 pg/mL, p = 0.02; interleukin-8: 70.75 vs 27.86 pg/mL, p = 0.002; interleukin-6: 67.50 vs 21.81 pg/mL, p = 0.005; and interleukin-10: 30.98 vs 12.60 pg/mL, p < 0.001). Interleukin-17A levels were similar between groups at both time points. After controlling for confounding variables by multivariate analysis, interleukin-10/tissue necrosis factor ratio at 72 hours most significantly predicted persistence (odds ratio, 2.98; 95% CI, 1.39-6.39; p = 0.005) and mortality (odds ratio, 9.87; 95% CI, 2.64-36.91; p < 0.001) at values more than 1.00 and more than 2.56, respectively. CONCLUSIONS: Sustained elevation of interleukin-10/tissue necrosis factor ratio at 72 hours suggests a dysregulated immune response and may be used to guide management to improve outcomes.

Comparative Effectiveness of Vancomycin Versus Daptomycin for MRSA Bacteremia With Vancomycin MIC >1 mg/L: A Multicenter Evaluation.

PURPOSE: Clinical studies comparing vancomycin with alternative therapy for methicillin-resistant Staphylococcus aureus (MRSA) bacteremia are limited. The objective of this study was to compare outcomes of early daptomycin versus vancomycin treatment for MRSA bacteremia with high vancomycin MICs in a geographically diverse multicenter evaluation. METHODS: This nationwide, retrospective, multicenter (N = 11), matched, cohort study compared outcomes of early daptomycin with vancomycin for MRSA bloodstream infection (BSI) with vancomycin MICs 1.5 to 2 µg/mL. Matching variables, based on propensity regression analysis, included age, intensive care unit (ICU), and type of BSI. Outcomes were as follows: (1) composite failure (60-day all-cause mortality, 7-day clinical or microbiologic failure, 30-day BSI relapse, or end-of-treatment failure (EOT; discontinue/change daptomycin or vancomycin because of treatment failure or adverse event]); (2) nephrotoxicity; and (2) day 4 BSI clearance. FINDINGS: A total of 170 patients were included. The median (interquartile range) age was 60 years (50-74); the median (range) Acute Physiology and Chronic Health Evaluation II score was 15 (10-18); 31% were in an ICU; and 92% had an infectious disease consultation. BSI types included endocarditis/endovascular (39%), extravascular (55%), and central catheter (6%). The median daptomycin dose was 6 mg/kg, and the vancomycin trough level was 17 mg/L. Overall composite failure was 35% (59 of 170): 15% due to 60-day all-cause mortality, 14% for lack of clinical or microbiologic response by 7 days, and 17% due to failure at end of therapy (discontinue/change because of treatment failure or adverse event). Predictors of composite failure according to multivariate analysis were age >60 years (odds ratio, 3.7; P < 0.01) and ICU stay (odds ratio, 2.64; P = 0.03). Notable differences between treatment groups were seen with: (1) end of therapy failure rates (11% vs 24% for daptomycin vs vancomycin; P = 0.025); (2) acute kidney injury rates (9% vs 23% for daptomycin vs vancomycin; P = 0.043); and (3) day 4 bacteremia clearance rates for immunocompromised patients (n = 26) (94% vs 56% for daptomycin vs vancomycin; P = 0.035). IMPLICATIONS: Results from this multicenter study provide, for the first time, a geographically diverse evaluation of daptomycin versus vancomycin for patients with vancomycin-susceptible MRSA bacteremia with vancomycin MIC values >1 µg/mL. Although the overall composite failure rates did not differ between the vancomycin and daptomycin groups when intensively matched according to risks for failure, the rates of acute kidney injury were significantly lower in the daptomycin group. These findings suggest that daptomycin is a useful therapy for clinicians treating patients who have MRSA bacteremia. Prospective, randomized trials should be conducted to better assess the potential significance of elevated vancomycin MIC.

Risk of developing pneumonia is enhanced by the combined traits of fluoroquinolone resistance and type III secretion virulence in respiratory isolates of Pseudomonas aeruginosa.

OBJECTIVES: To determine the differential association of host characteristics, antimicrobial resistance, and type III secretion system virulence of Pseudomonas aeruginosa isolates with respiratory syndromes in hospitalized adult patients. DESIGN: Retrospective, cohort study. SETTING: Community teaching hospital. PATIENTS: Two hundred eighteen consecutive adult patients with respiratory culture positive for P. aeruginosa between January 2005 to January 2010. INTERVENTIONS: Medical charts were reviewed to obtain demographic, laboratory, radiographic, and clinical information. Isolates were assayed by polymerase chain reaction for genes encoding the type III secretion system effectors (ExoU, ExoS, and PcrV) and for strain relatedness using randomly amplified polymorphic DNA analysis. Levofloxacin susceptibility was determined by broth microdilution. Patients were grouped by colonization, bronchitis, or pneumonia and were compared for differential risk of developing the clinical syndrome with respect to host and microbial characteristics. MEASUREMENTS AND MAIN RESULTS: Half of the study cohort (54%, 117 of 218) had pneumonia, 32% (70 of 218) had bronchitis, and 14% (31 of 218) had colonization; in-hospital mortality was 35%, 11%, and 0%, respectively. Host factors strongly associated with pneumonia development were residence in long-term care facility, healthcare-associated acquisition of P. aeruginosa, higher Acute Physiology and Chronic Health Evaluation II score, presence of enteral feeding tube, mechanical ventilation, and recent history of pneumonia. Fluoroquinolone-resistant (57% vs 34%, 16%; p < 0.0001) and multidrug-resistant (36% vs 26%, 7%; p = 0.0045) strains were more likely to cause pneumonia than bronchitis or colonization, respectively. Analysis of host and microbial factors in a multivariate regression model yielded the combined traits of fluoroquinolone resistance and gene encoding the type III secretion system ExoU effector in P. aeruginosa as the single most significant predictor of pneumonia development. CONCLUSIONS: These results suggest that fluoroquinolone-resistant phenotype in a type III secretion system exoU strain background contributes toward the pathogenesis of P. aeruginosa in pneumonia.