Program Schedule

Association between acessory gene regulator II expression and mortality among critically ill patients receiving vancomycin for hospital-acquired methicillin-resistant Staphylococcus aureus bacteremia

Session: Poster Abstract Session: MRSA and VRE
Thursday, October 9, 2014
Room: The Pennsylvania Convention Center: IDExpo Hall BC
  • IDWEEK_MRSA_2014.pdf (5.0 MB)
  • Background: The polymorphism of the accessory gene regulator (agr) of methicillin-resistant Staphylococcus aureus (MRSA) is known to play an important role in controlling the production of virulence factors. Notably, infections caused by MRSA with agr-II expression are shown to be predictive of vancomycin therapy failure.  However, the impact of agr-II expression on mortality of patients receiving vancomycin therapy for severe MRSA infections is not well established. The aim of this study was to evaluate the association between agr-II expression and 30-day mortality among critically ill patients receiving vancomycin therapy for hospital-acquired MRSA bacteremia.

    Methods: A retrospective cohort was performed at a 30-bed general intensive care unit (ICU) of a tertiary hospital in southern Brazil. All cases of documented hospital-acquired MRSA bacteremia treated with vancomycin in the ICU setting between May 2009 and November 2011 were evaluated. Cox regression was performed to evaluate whether agr-II expression (determined by PCR) was associated with 30-day mortality. Covariates included age, presence of immunossuppression, APACHE-II score, initial C-reactive protein (CRP) plasma levels, initial serum creatinine levels, vancomycin minimum inhibitory concentration, vancomycin serum levels and time to effective antibiotic administration.

    Results: In total, 21 patients were evaluated during the study period. The prevalence of agr-II expression was 38% (8 patients). The median APACHE-II of the study population was 23 (IQR, 19 to 31). The overall cohort mortality was 61% (13 patients). After multivariate analysis, initial plasma CRP (P=0.01), initial serum creatinine (P=0.03) and expression of agr-II (P=0.02) were independently associated with the 30-day mortality. Patients receiving vancomycin therapy for bacteremia due to MRSA with agr-II expression had their hazard of death increased by 6.6 times (95%CI, 1.2-37.0) when compared with those with bacteremia by MRSA without agr-II expression.

    Conclusion: Expression of agr-II poses risk for mortality in critically ill patients receiving vancomycin for hospital-acquired MRSA bacteremia.  Alternative antimicrobial agents including daptomycin and linezolid for  treatment  of MRSA bacteremia expressing agr-II  should be considered in this setting.

    Regis Rosa, M.D. M.S.1, Eduardo Turra2, Denise Machado, PhD3, Angelica Cechinel2, Rodrigo Dos Santos, MD, PhD4 and Luciano Goldani, PhD, MD5, (1)PPG Em Ciências Médicas, Ufrgs - Faculty of Medicine, Porto Alegre, Brazil, (2)Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil, (3)Ufrgs, Porto Alegre, Brazil, (4)Hospital de Clinicas de Porto Alegre / Universidade Federal do Rio Grande do Sul, Prto Alegre, Brazil, (5)Infectious Diseases Unit, Hospital de Clinicas de Porto Alegre, Porto Alegre, Brazil


    R. Rosa, None

    E. Turra, None

    D. Machado, None

    A. Cechinel, None

    R. Dos Santos, None

    L. Goldani, None

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