Febrile Urinary Tract Infection in Infants
A 6-month-old uncircumcised boy has a 2-day fever up to 39.2 °C and irritability. He is alert and drinking well from a bottle, with moist mucous membranes and no vomiting. A catheter urine sample shows positive nitrites and leucocyte esterase with 60 white cells per high power field, and culture has been sent. What is the most appropriate antibiotic therapy?
- A.Oral cefuroxime for 7 to 10 daysCorrect
- B.Intravenous ceftriaxone for 10 days
- C.Intravenous cefepime for 10 days
- D.Oral amoxicillin-clavulanate for 3 days
Explanation
This infant has a febrile urinary tract infection, most likely pyelonephritis, diagnosed on a catheter specimen showing pyuria with positive nitrites while awaiting culture. Randomised evidence and the AAP guideline show that for infants older than 2 months who are not toxic, are well hydrated, and can tolerate oral fluids, oral therapy is as effective as intravenous therapy in eradicating infection and preventing renal scarring, so an oral second or third generation cephalosporin such as cefuroxime or cefixime is the appropriate choice for a total of 7 to 14 days. The parenteral route is reserved for infants under 2 months of age, toxic or septic appearance, dehydration, persistent vomiting preventing oral intake, or failure to improve after 48 to 72 hours of oral therapy, and children started intravenously are stepped down to oral therapy once afebrile and tolerating feeds. Cefepime is an antipseudomonal fourth generation agent whose spectrum is unnecessarily broad for community acquired infection and encourages resistance. Amoxicillin-clavulanate is a weaker choice because local Escherichia coli resistance to aminopenicillins is high, and a 3-day course is appropriate only for lower tract cystitis in older children, never for febrile upper tract infection. Uncircumcised male infants carry a several fold higher risk of urinary tract infection than circumcised boys, especially in the first year of life. Renal and bladder ultrasound should be arranged after a first febrile urinary tract infection in an infant, with voiding cystourethrography reserved for abnormal ultrasound findings or recurrent febrile infections. Definitive therapy is then narrowed once culture and sensitivities return.
Why each option
- A.
- Correct. A well hydrated, non-toxic infant older than 2 months who tolerates oral intake can be treated with an oral second or third generation cephalosporin for 7 to 14 days.
- B.
- Intravenous ceftriaxone is reserved for infants under 2 months, toxic appearance, dehydration, or inability to tolerate oral therapy, none of which apply here.
- C.
- Cefepime offers unnecessary antipseudomonal coverage for community acquired urinary infection and drives resistance without added benefit.
- D.
- Aminopenicillin resistance among Escherichia coli is high, and a 3-day course is inadequate for a febrile upper tract infection.
Reference: AAP Clinical Practice Guideline: Urinary Tract Infection in Febrile Infants and Young Children, reaffirmed 2022
This is one of 3,009 questions in the MedBoardSA SMLE bank, with timed test mode, tutor mode, and progress tracking by topic.
Practise the full bank