For a 4-week-old infant with fever, poor feeding, and otitis media, which antibiotic is best to administer?

In this scenario involving a 4-week-old infant presenting with fever, poor feeding, and otitis media, the most appropriate antibiotic to administer is a combination of ampicillin and ceftriaxone. This choice is underpinned by the need for broad-spectrum coverage due to the infant's age and acute presentation.

Infants under three months are at a higher risk for serious infections, and their clinical signs, such as fever and poor feeding, warrant a thorough and aggressive approach to treatment. Ampicillin is effective against common pathogens in this age group, including Group B Streptococcus and Listeria monocytogenes. Ceftriaxone adds coverage for certain resistant strains of Streptococcus pneumoniae, which is particularly crucial given the recent prevalence of antibiotic resistance.

This combination ensures that a range of potential pathogens associated with both otitis media and systemic infections (such as meningitis or sepsis) are effectively targeted. In young infants, such considerations are paramount to avoid delayed therapy for serious bacterial infections, which can lead to significant morbidity.

While other options like cefazolin, amoxicillin, and clindamycin have their roles in treating various infections, they do not provide the same broad coverage needed for a high-risk infant.