What is the best course of action for a patient with urine positive for signs of infection (White Blood Cells (WBC), Red Blood Cells (RBC), blood, protein, leukocytes, casts) but a urine culture showing mixed bacteria with no sensitivity results?

From the Guidelines

For a patient with urinary symptoms and a urinalysis showing signs of infection (WBC, RBC, blood, protein, leukocytes, casts) but a urine culture with mixed bacteria and no sensitivity results, empiric antibiotic therapy should be initiated with fluoroquinolones or cephalosporins, as they are the only recommended antimicrobial agents for oral empiric treatment of uncomplicated pyelonephritis. According to the European Association of Urology guidelines on urological infections 1, fluoroquinolones and cephalosporins are the preferred choices for oral empiric treatment. I recommend starting with ciprofloxacin 250-500mg twice daily for 3-7 days, as it is a commonly used fluoroquinolone for treating urinary tract infections.

Some key points to consider when treating this patient include:

• A repeat urine culture should be collected before starting antibiotics if possible, to confirm the diagnosis and identify the causative organism.
• The mixed bacteria result likely represents contamination during collection, so proper midstream clean-catch technique should be emphasized for the repeat sample.
• Increased fluid intake and urinary analgesics like phenazopyridine 200mg three times daily for 2 days can help manage symptoms.
• It is essential to monitor the patient's response to treatment and adjust the antibiotic regimen as needed, based on the results of the repeat urine culture and sensitivity testing.

The approach is justified because untreated urinary tract infections can progress to more serious conditions like pyelonephritis or sepsis, while the mixed culture result suggests sample contamination rather than absence of infection in a symptomatic patient with abnormal urinalysis findings. The guidelines from the European Association of Urology 1 support the use of fluoroquinolones and cephalosporins as the primary treatment options for uncomplicated pyelonephritis, making them the best choice for empiric antibiotic therapy in this case.

From the Research

Urine Infection Diagnosis and Treatment

• The patient's urine test shows signs of infection, including White Blood Cells (WBC), Red Blood Cells (RBC), blood, protein, leukocytes, and casts, indicating a potential urinary tract infection (UTI) 2, 3, 4.
• However, the urine culture shows mixed bacteria with no sensitivity results, making it challenging to determine the best course of action for treatment.

Mixed Bacteria in Urine Culture

• A study published in the Journal of Medical Microbiology found that mixed growth urine cultures (MGUC) are common, accounting for 12.4% of urine specimens processed in 2018 5.
• The same study found that Enterococcus species and Escherichia coli were the most frequently isolated organisms in MGUC, and that 65.5% of cultures contained two organisms.
• Clinicians believed that MGUC reports represented the detection of many commensal bacteria, but were more likely to diagnose and treat a UTI when provided with detailed microbial analysis of MGUC, including identity and antibiotic sensitivity of organisms 5.

Treatment Options

• A study published in the Annals of Family Medicine found that antibiotic resistance is a significant concern in the treatment of UTIs, with high resistance rates to commonly used antibiotics such as trimethoprim-sulfamethoxazole and ciprofloxacin 2.
• The same study found that factors such as prior UTI, prior fluoroquinolone use, and complicated UTI increased the odds of antibiotic resistance.
• Another study published in Expert Opinion on Investigational Drugs found that ciprofloxacin extended release is a effective treatment option for UTIs, with a high clinical cure and bacteriological eradication rate 4.
• A study published in Pharmacy found that implementation of a UTI treatment protocol that emphasized correct UTI diagnosis and use of nitrofurantoin and cefpodoxime/ceftriaxone as empiric therapy per the institutional antibiogram improved prescribing practices and decreased the use of inappropriate antimicrobials 6.

Next Steps

• Given the mixed bacteria in the urine culture and the lack of sensitivity results, it may be necessary to repeat the urine culture or perform further testing to determine the best course of action for treatment.
• Clinicians should consider the patient's medical history, including prior UTIs and antibiotic use, as well as the results of the urine culture and sensitivity testing, when selecting an antibiotic for treatment 2, 3, 4, 6, 5.