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Open Access Highly Accessed Research article

Staphylococcus aureus bacteriuria as a prognosticator for outcome of Staphylococcus aureus bacteremia: a case-control study

Shingo Chihara1*, Kyle J Popovich23, Robert A Weinstein23 and Bala Hota23

Author Affiliations

1 Department of Clinical Laboratory Medicine, Dokkyo Medical University, Tochigi, Japan

2 Section of Infectious Diseases, Department of Medicine, Rush University Medical Center, 600 S Paulina, Suite 143 Academic Facility, Chicago, IL 60612, USA

3 Division of Infectious Diseases, Department of Medicine, John H. Stroger Jr. Hospital of Cook County (CCH), Chicago, Illinois, USA

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BMC Infectious Diseases 2010, 10:225  doi:10.1186/1471-2334-10-225

Published: 29 July 2010

Abstract

Background

When Staphylococcus aureus is isolated in urine, it is thought to usually represent hematogenous spread. Because such spread might have special clinical significance, we evaluated predictors and outcomes of S. aureus bacteriuria among patients with S. aureus bacteremia.

Methods

A case-control study was performed at John H. Stroger Jr. Hospital of Cook County among adult inpatients during January 2002-December 2006. Cases and controls had positive and negative urine cultures, respectively, for S. aureus, within 72 hours of positive blood culture for S. aureus. Controls were sampled randomly in a 1:4 ratio. Univariate and multivariable logistic regression analyses were done.

Results

Overall, 59% of patients were African-American, 12% died, 56% of infections had community-onset infections, and 58% were infected with methicillin-susceptible S. aureus (MSSA). Among 61 cases and 247 controls, predictors of S. aureus bacteriuria on multivariate analysis were urological surgery (OR = 3.4, p = 0.06) and genitourinary infection (OR = 9.2, p = 0.002). Among patients who died, there were significantly more patients with bacteriuria than among patients who survived (39% vs. 17%; p = 0.002). In multiple Cox regression analysis, death risks in bacteremic patients were bacteriuria (hazard ratio 2.9, CI 1.4-5.9, p = 0.004), bladder catheter use (2.0, 1.0-4.0, p = 0.06), and Charlson score (1.1, 1.1-1.3, p = 0.02). Neither length of stay nor methicillin-resistant Staphylococcus aureus (MRSA) infection was a predictor of S. aureus bacteriuria or death.

Conclusions

Among patients with S. aureus bacteremia, those with S. aureus bacteriuria had 3-fold higher mortality than those without bacteriuria, even after adjustment for comorbidities. Bacteriuria may identify patients with more severe bacteremia, who are at risk of worse outcomes.