What is the most appropriate next step in managing a febrile 6-month-old ill-appearing infant with signs of a urinary tract infection?

In managing an ill-appearing 6-month-old infant with signs of a urinary tract infection (UTI) and fever, initiating intravenous (IV) antibiotics, specifically ceftriaxone, is the most appropriate next step. This approach is important because infants in this age group, especially those who appear ill, can be at risk for serious infections and potential complications.

Intravenous therapy allows for rapid administration of higher antibiotic levels that are effective against a larger spectrum of bacteria, which is crucial since UTI can be caused by various organisms, including those resistant to oral antibiotics. Administering IV ceftriaxone ensures adequate coverage while also providing the necessary fluid management that can be pivotal in a young infant who may present with dehydration or difficulty maintaining oral intake.

In addition, ill appearance in the context of fever raises concern for possible systemic infection beyond UTI, such as meningitis or sepsis, which further justifies the need for immediate and aggressive management, such as IV antibiotics. Other options, like administering oral antibiotics or discharging with follow-up, could lead to delays in treatment and are not suitable for a patient with significant illness. A lumbar puncture could be considered in some cases but is more appropriate when meningitis is suspected specifically