Pneumonia Caused by Methicillin-Resistant Staphylococcus aureus – Does Vancomycin Heteroresistance Matter?

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Pneumonia Caused by Methicillin-Resistant Staphylococcus aureus - Does Vancomycin Heteroresistance Matter?

Antimicrob Agents Chemother. 2016 Jan 4;

Authors: Claeys KC, Lagnf AM, Hallesy JA, Compton MT, Gravelin AL, Davis SL, Rybak MJ

BACKGROUND: Vancomycin remains the mainstay treatment for methicillin-resistant S. aureus (MRSA) infections, including pneumonia. There is concern regarding the emergence of vancomycin tolerance, caused by heterogeneous vancomycin-intermediate S. aureus (hVISA), and subsequent vancomycin treatment failure. Pneumonia is associated with high morbidity and mortality, especially with delays in appropriate therapy. This study evaluated the clinical outcomes of patients with hVISA compared to vancomycin-susceptible S. aureus (VSSA) pneumonia.
METHODS: Retrospective cohort of patients with MRSA pneumonia from 2005 to 2014 matched 2:1 VSSA to hVISA to compare patient characteristics, treatments, and outcomes. hVISA determined by the 48-hour population analysis profile/area-under-the-curve. Characteristics between VSSA and hVISA were compared by univariate analysis and multivariable logistic regression analysis to determine independent risk factors of inpatient mortality.
RESULTS: Eighty-seven patients were included: 29 hVISA and 58 VSSA pneumonias. There were no significant differences in demographics or baseline characteristics. Sequential Organ Failure Assessment (SOFA) scores were a median of 7 (IQR 5 - 8) in hVISA patients and 5 (IQR 3 - 8) in VSSA (p = 0.092) patients. Inpatient mortality was significantly higher in hVISA patients (44.8% versus 24.1%, p = 0.049). Predictors of inpatient mortality on multivariable regression were SOFA score (aOR 1.36; 95% CI 1.08 - 1.70), PVL positivity (aOR 6.63; 95% CI 1.79 - 24.64); and hVISA phenotype (aOR 3.95; 95% CI 1.18 - 13.21).
CONCLUSIONS: Patients with hVISA pneumonia experienced significantly higher inpatient mortality than those with VSSA. There is a need to consider the presence of vancomycin heteroresistance in pneumonia caused by MRSA in order to potentially improve clinical outcomes.

PMID: 26729497 [PubMed - as supplied by publisher]

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