When Staphylococcus aureus is isolated in urine, it is thought to usually represent hematogenous spread. Because such spread might have special clinical significance, Shingo Chihara and colleagues evaluated predictors and outcomes of S. aureus bacteriuria among patients with S. aureus bacteremia.
The researchers performed a case-control study at John H. Stroger Jr. Hospital of Cook County in Illinois, among adult inpatients during January 2002 through 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.
Overall, 59 percent of patients were African-American, 12 percent died, 56 percent of infections had community-onset infections, and 58 percent 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 percent vs. 17 percent; 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.
The researchers concluded that among patients with S. aureus bacteremia, those with S. aureus bacteriuria had three-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. The research was published in BMC Infectious Diseases.
Reference: Chihara S, Popovich KJ , Weinstein RA and Hota B. Staphylococcus aureus bacteriuria as a prognosticator for outcome of Staphylococcus aureus bacteremia: a case-control study. BMC Infectious Diseases 2010, 10:225doi:10.1186/1471-2334-10-225