What is the recommended treatment for a 6-month-old infant with a urine culture showing multi-drug resistant Escherichia coli (E. coli), pyuria (60 pus cells), and who is asymptomatic?

Management of Multi-Drug Resistant E. coli UTI in a 6-Month-Old Asymptomatic Infant

For a 6-month-old infant with asymptomatic multi-drug resistant E. coli UTI with pyuria (60 pus cells), meropenem is the recommended treatment at a dose of 20 mg/kg IV every 8 hours for 7-10 days. 1

Diagnostic Considerations

The presence of pyuria (60 pus cells) with a positive culture for multi-drug resistant E. coli indicates a true UTI rather than colonization, even in the absence of symptoms. This is particularly concerning in infants under 1 year of age, where:

• Asymptomatic infections can still lead to renal scarring
• Infants may not present with typical UTI symptoms
• Multi-drug resistant organisms require careful antibiotic selection

Treatment Algorithm

First-line Treatment:

• Meropenem: 20 mg/kg/dose IV every 8 hours 1, 2
  • Appropriate for complicated intra-abdominal infections in infants
  • Effective against multi-drug resistant gram-negative organisms
  • For infants 3-6 months, administer as intravenous infusion over 15-30 minutes

Alternative Options (if susceptibility confirmed):

1. Ceftazidime-avibactam: 40 mg/kg/dose IV every 8 hours (for infants 3-6 months) 1

   • Recommended for complicated UTIs caused by CRE
   • Limited pediatric data but approved for children ≥3 months

2. Amikacin: 15-22.5 mg/kg/dose IV every 24 hours 1

   • Effective for many multi-drug resistant gram-negative infections
   • Requires therapeutic drug monitoring

Treatment Duration and Monitoring

• Duration: 7-10 days for complicated UTI with multi-drug resistant organism
• Monitoring:
  • Clinical response within 48-72 hours
  • Follow-up urine culture after completing treatment
  • Renal function tests during treatment

Special Considerations for Infants

1. Imaging: Renal ultrasound should be performed to rule out anatomical abnormalities 1

   • Infants with UTI have higher incidence of urinary anomalies
   • Presence of MDR organism increases risk of complications

2. Risk factors for MDR E. coli in infants 3:

   • Genitourinary tract anomalies (OR 2.42)
   • Previous antibiotic use (OR 2.62)
   • Presence of invasive devices (OR 3.48)

3. Follow-up: Consider voiding cystourethrography (VCUG) if:

   • Abnormal ultrasound findings
   • Recurrent UTI episodes
   • Poor response to appropriate antibiotics

Pitfalls to Avoid

1. Do not delay treatment despite asymptomatic presentation

   • MDR infections in infants can rapidly progress to systemic illness
   • Delays in effective therapy are associated with longer hospitalization 3

2. Do not use empiric antibiotics without susceptibility testing

   • Only 47% of children with MDR infections receive effective empiric antibiotics 3
   • Treatment should be guided by culture results

3. Avoid unnecessary broad-spectrum antibiotics

   • De-escalate therapy once susceptibility results are available
   • Prevent further antimicrobial resistance development

4. Do not rely on pyuria alone for diagnosis

   • While pyuria suggests infection, 71.4% of neonates with pyuria may have negative cultures 4
   • Always correlate with culture results

The management of MDR E. coli UTI in infants requires prompt, appropriate antibiotic therapy guided by susceptibility testing, with careful monitoring for complications and consideration of underlying anatomical abnormalities.