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Antibiotic choice may not explain poorer outcomes in patients with Staphylococcus aureus bacteremia and high vancomycin minimum inhibitory concentrations

Holmes, N.E., Turnidge, J.D., Munckhof, W.J., Robinson, J.O., Korman, T.M., O'Sullivan, M.V.N., Anderson, T.L., Roberts, S.A., Gao, W., Christiansen, K.J., Coombs, G.W., Johnson, P.D.R. and Howden, B.P. (2011) Antibiotic choice may not explain poorer outcomes in patients with Staphylococcus aureus bacteremia and high vancomycin minimum inhibitory concentrations. Journal of Infectious Diseases, 204 (3). pp. 340-347.

Free to read: http://dx.doi.org/10.1093/infdis/jir270
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Abstract

Background. There are concerns about reduced efficacy of vancomycin in patients with Staphylococcus aureus bacteremia (SAB), especially when the minimum inhibitory concentration (MIC) nears the upper limit of the susceptible range. Methods. We examined the relationship between antibiotic treatment, 30-day mortality, and microbiologic parameters in a large Australasian cohort of patients with SAB. Results. We assessed 532 patients with SAB from 8 hospitals. All patients with methicillin-resistant S. aureus (MRSA) bacteremia were treated with vancomycin, and patients with methicillin-susceptible S. aureus (MSSA) bacteremia received either flucloxacillin or vancomycin. Increasing vancomycin MIC was associated with increased mortality in vancomycin-treated patients. However, even in patients with MSSA bacteremia treated with flucloxacillin, mortality was also higher if the vancomycin Etest MIC of their isolate was >1.5 μg/mL, compared with thosewith lower MIC isolates (26.8% vs 12.2%; P < .001). After adjustment in a multivariate model, age, hospital-onset SAB and vancomycin MIC were independently associated with mortality, butmethicillin resistance and antibiotic choice were not. Conclusions. We have confirmed an association between higher vancomycin MIC and increased mortality in patients with SAB, but surprisingly this relationship was not related to the antibiotic treatment received, suggesting that the use of vancomycin per se is not responsible for the poorer outcome.

Publication Type: Journal Article
Publisher: Oxford University Press
Copyright: © The Author 2011.
URI: http://researchrepository.murdoch.edu.au/id/eprint/30638
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