Management of Citrobacter koseri UTI with Hematuria in a Male Patient
Treat this as a complicated urinary tract infection requiring 7–14 days of antimicrobial therapy guided by susceptibility testing, while simultaneously pursuing urgent urologic evaluation for the hematuria. 1
Immediate Antibiotic Management
Empiric Therapy (Pending Susceptibilities)
Start empiric therapy immediately with a fluoroquinolone (ciprofloxacin 500 mg orally twice daily or levofloxacin 750 mg once daily) for 7–10 days if local resistance is <10%, as this is appropriate for complicated UTI or suspected pyelonephritis when systemic signs are present. 1
Alternatively, use an intravenous third-generation cephalosporin (ceftriaxone 1–2 g daily) or amoxicillin plus an aminoglycoside for severe cases, particularly if the patient has fever, rigors, hypotension, or other systemic signs. 1
All UTIs in men are classified as complicated and require a minimum of 7 days of therapy regardless of the chosen agent. 1
Definitive Therapy Based on Susceptibilities
Adjust antibiotics according to culture susceptibility results as soon as available, because Citrobacter koseri exhibits inherent resistance to ampicillin and emerging resistance to beta-lactams and aminoglycosides, often requiring carbapenem therapy. 2
If susceptibilities show resistance to fluoroquinolones or cephalosporins, switch to a carbapenem (e.g., meropenem or ertapenem) for the remainder of the 7–14 day course. 2
The colony count of >100,000 CFU/mL with a single predominant organism (Citrobacter koseri) in a symptomatic male patient is diagnostic of UTI, meeting the threshold for treatment. 1
Hematuria Evaluation: Urgent and Mandatory
Why Hematuria Cannot Be Ignored
Gross hematuria (visible blood) carries a 30–40% risk of underlying malignancy and requires urgent urologic evaluation with cystoscopy and upper-tract imaging, even if the bleeding appears self-limited. 3
The presence of "packed RBCs" and occult blood on dipstick suggests significant hematuria that must be confirmed with microscopic urinalysis showing ≥3 RBCs per high-power field before initiating any further workup. 3
Do not attribute hematuria solely to the UTI or anticoagulation/antiplatelet therapy; these may unmask underlying pathology but do not cause hematuria themselves, and evaluation must proceed regardless. 3
Immediate Diagnostic Steps
Order a microscopic urinalysis on a properly collected clean-catch midstream specimen to confirm ≥3 RBCs/HPF, as dipstick testing alone has only 65–99% specificity and can yield false positives. 3, 4
Obtain serum creatinine and BUN to assess renal function, as elevated creatinine with hematuria and proteinuria signals renal parenchymal disease. 3
Examine urinary sediment for dysmorphic RBCs (>80% suggests glomerular origin) and red cell casts (pathognomonic for glomerular disease), which would indicate nephrology referral in addition to urologic evaluation. 3
Perform a spot urine protein-to-creatinine ratio to quantify proteinuria, as values >0.5 g/g strongly suggest renal parenchymal disease and warrant nephrology consultation. 3
Imaging and Endoscopic Evaluation
Multiphasic CT urography (unenhanced, nephrographic, and excretory phases) is the preferred imaging modality for detecting renal cell carcinoma, transitional cell carcinoma, and urolithiasis, with 96% sensitivity and 99% specificity for urothelial malignancy. 3
Flexible cystoscopy is mandatory for all males ≥40 years with confirmed microscopic hematuria to directly visualize the bladder mucosa, urethra, and ureteral orifices, as bladder cancer accounts for 30–40% of gross hematuria cases and cannot be excluded by imaging alone. 3
Do not delay cystoscopy while treating the UTI; imaging and endoscopy should proceed concurrently with antibiotic therapy, as infection does not exclude serious urologic pathology. 3
Risk Stratification for Hematuria
High-Risk Features Requiring Full Urologic Workup
Age ≥60 years (both men and women) automatically classifies the patient as high-risk, requiring both cystoscopy and CT urography regardless of other factors. 4
Smoking history >30 pack-years, occupational exposure to chemicals/dyes (benzenes, aromatic amines), history of gross hematuria, and irritative voiding symptoms without infection are additional high-risk features that mandate complete urologic evaluation. 4
The presence of "packed RBCs" suggests a high degree of hematuria (likely >25 RBCs/HPF), which is itself a high-risk feature requiring full evaluation. 4
Special Considerations for Citrobacter koseri
Polymicrobial vs. Monomicrobial Infection
The urine culture showing >100,000 CFU/mL of Citrobacter koseri as a single predominant organism represents true infection, not contamination, as mixed flora would indicate specimen contamination. 5
True polymicrobial UTIs are rare (<3–11% of cases) and occur only in high-risk settings such as structural urinary abnormalities, neurogenic bladder, or long-term indwelling catheters, which do not appear to be present in this case. 1
Citrobacter koseri as an Emerging Pathogen
Citrobacter koseri is increasingly recognized as a pathogen in immunocompetent adults, not just neonates and immunocompromised patients, as demonstrated by cases of infective endocarditis and osteomyelitis in healthy individuals. 2, 6, 7
Citrobacter species have been implicated in nosocomial infections involving the urinary tract, respiratory tract, liver, biliary tract, meninges, and bloodstream, with gram-negative bacilli responsible for 3–4% of all infective endocarditis cases. 2
Patients with non-HACEK gram-negative bacilli infective endocarditis have poor clinical outcomes with higher rates of in-hospital mortality and complications, underscoring the importance of appropriate antibiotic therapy. 2
Follow-Up and Monitoring
Reassessment of Clinical Response
Re-evaluate clinical response within 48–72 hours of initiating therapy; if symptoms persist or worsen, modify antibiotics based on susceptibility results and consider imaging (ultrasound or CT) to rule out obstruction, stones, or abscess. 1
If fever persists >72 hours despite appropriate therapy, obtain contrast-enhanced CT to assess for complications such as renal abscess. 1
Hematuria Follow-Up
If the initial urologic workup is negative but hematuria persists, repeat urinalysis at 6,12,24, and 36 months with blood pressure monitoring at each visit. 3, 4
Immediate re-evaluation is warranted if gross hematuria develops, significant increase in microscopic hematuria occurs, new urologic symptoms appear, or development of hypertension/proteinuria/glomerular bleeding. 3, 4
Critical Pitfalls to Avoid
Do not treat based solely on pyuria or bacteriuria without confirming urinary symptoms; asymptomatic bacteriuria occurs in 15–50% of older adults and should not be treated. 1
Never ignore gross hematuria, even if self-limited, due to the 30–40% malignancy risk that mandates urgent urologic referral. 3
Do not assume hematuria is solely infection-related; infection may mask cancer, and systematic evaluation is required to avoid missed malignancy. 3
Do not delay urologic evaluation while treating the UTI; age and hematuria alone are sufficient risk factors for full workup. 3
Do not attribute hematuria to anticoagulation or antiplatelet therapy without completing the recommended urologic workup, as these agents may unmask underlying pathology but are not causative. 3