Snapshot A 24-year-old woman at 8 weeks of gestation presents to her obstetrician for increased urinary frequency, dysuria, and some suprapubic pressure for the past few days. She has a history of spontaneous abortions. On physical exam, she has suprapubic tenderness to palpation and right costovertebral tenderness. A rapid urine dipstick shows nitrite, leukocyte esterase, and urease positivity. She is started on an antibiotic that is safe for pregnant women. Introduction Classification Proteus spp. P. mirabilis (most common, both community-acquired and nosocomial) P. vulgaris (nosocomial) urease-positive, oxidase-negative, and non-lactose fermenting gram-negative bacillus causes urinary tract infections (UTI) Epidemiology incidence very common demographics women > men risk factors urinary catheter urinary tract obstruction living in nursing home hospital admission immunocompromised status Pathogenesis increased inoculum size is correlated with risk of infection the bacteria attach to the urinary tract endothelium can produce endotoxin that can lead to sepsis hydrolyzes urea to ammonia, which alkalinizes the urine Associated conditions struvite kidney stones Prognosis mortality is low with treatment Presentation Symptoms dysuria urinary frequency flank pain Physical exam costovertebral tenderness suprapubic tenderness Imaging Abdominal computed tomography (CT) indication evaluate for kidney stones findings radiopaque stones Studies Urine culture “swarming” motility on agar plate Urine dipstick leukocyte esterase positive nitrite positive urease positive pH alkaline Making the diagnosis based on clinical presentation and laboratory studies Differential E. coli urinary tract infection distinguishing factor urinalysis does not show urease positivity Treatment Management approach final choice of antibiotics depends on whether or not a UTI is uncomplicated vs complicated and the sensitivities of cultured bacteria uncomplicated UTI acute cystitis or pyelonephritis in outpatient women who are not pregnant and do not have anatomic abnormalities or instrumentation within the urinary tract complicated UTI patients who do not meet uncomplicated UTI criteria Medical trimethoprim/sulfamethoxazole or nitrofurantoin indication first-line for uncomplicated UTI second-line agents include fluoroquinolone or β-lactam fluoroquinolone indication first-line for acute uncomplicated pyelonephritis nitrofurantoin or cephalosporins indication pregnant women Complications Urosepsis Struvite stones