Proteus mirabilis urinary tract infection and bacteremia: Risk factors, clinical presentation, and outcomes

BACKGROUND/PURPOSE: Proteus mirabilis is a common pathogen responsible for complicated urinary tract infections (UTIs) that sometimes causes bacteremia. Most cases of P. mirabilis bacteremia originate from a UTI; however, the risk factors for bacteremia and mortality rates from P. mirabilis UTI have not been determined. METHODS: A retrospective, case-control study was performed between May 2008 and November 2010 to identify the risk factors and markers for P. mirabilis bacteremic UTI. Each subject in the case group (all patients were diagnosed with P. mirabilis bacteremia from a urinary tract source) was matched by age and gender to two subjects in the control group (patients diagnosed with P. mirabilis UTI but with negative blood culture results). Clinical presentation and laboratory data were analyzed to determine the risk factors and markers of P. mirabilis bacteremic UTI. RESULTS: Sixty-seven bacteremic UTIs and 124 nonbacteremic UTIs were included in this study. Community-acquired infection (p=0.017), hydronephrosis (p=0.017), band neutrophils accounting for >10% of the white blood cell count (p=0.001), hyperthermia or hypothermia (p=0.047), and a serum C-reactive protein concentration >100mg/L (p=0.002) were identified as independent risk factors for P. mirabilis bacteremic UTI. Seventeen patients died in hospital, including 11 in the bacteremic group and 6 in the nonbacteremic group. The bacteremic group had a higher mortality rate (p=0.016). Bacteremic UTI (p=0.049), shock (p=0.014), and a low body mass index (BMI) <18kg/m² (p=0.033) were identified as independent risk factors for mortality. CONCLUSION: Because bacteremic P. mirabilis UTIs are associated with higher mortality, clinicians should carefully manage cases that present with the risk factors for bacteremia, including community-acquired infection, hydronephrosis, band neutrophils accounting for >10% of the white blood cell count, hyperthermia or hypothermia, and a high level of C-reactive protein.