S. aureus bacteriuria (SABU) may represent multiple processes ranging from isolated urinary tract colonization to complications of S. aureus bacteremia (SAB). The significance of isolating S. aureus from the urinary tract is not yet fully appreciated.
A retrospective observational study was performed using a prospectively collected database. All urine cultures positive for S. aureus from individuals ≥18 years of age between January 2010 and December 2013 within the Calgary health region (43 health care centers and 12 acute care sites) were included. Subsequent urine samples collected within 90 days of the original urine culture, and of the same S. aureus susceptibilities, were excluded. Positive S. aureus blood cultures were included if they occurred within 90 days of a positive SABU. Patient characteristics were compared among patients with and without SAB and risk factors identified using multiple logistic regression.
A total of 2547 urine cultures positive for S. aureus were analyzed, 23% of which were MRSA. 18% were collected from urinary catheters. 85 (3%) had SAB. Those with SAB were more likely to be male (p<0.001), inpatients (p<0.001), admitted to ICU (p=0.014), have an invasive focus of infection (p=0.017), have higher white blood cell (WBC) levels (p<0.001) and have higher C-reactive protein (CRP) levels (p<0.001). Patients with isolated SABU were more likely to have urine WBC>30 (p<0.001) and have neurological disease (p<0.001). 88 (3.5%) of patients died. Risk factors for death included increasing age (p<0.001), inpatient status (p<0.001), diabetes (p=0.042), urological malignancy (p=0.004) and having SABU greater than 48 hours before SAB (p=0.008). Patients with recurrent SABU had lower mortality (p=0.021).
In the largest epidemiological study to date we describe the epidemiology of SABU. Interestingly, our data refutes previous SABU work suggesting high mortality rates. Specific demographics distinguish those with SAB from benign SABU; patients admitted to hospital, male gender, high systemic WBC and CRP, and normal urinalysis. Patients with SAB had increased mortality when SABU was detected >48 hours prior, likely due to delays in diagnosis and treatment.
M. Parkins, None
D. Gregson, None
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