For a patient with suspected cellulitis, which antibiotic is the most appropriate initial therapy?

The most appropriate initial therapy for a patient with suspected cellulitis is intravenous ampicillin-sulbactam. This antibiotic combination is effective against a broad range of bacteria, including the common pathogens associated with cellulitis, such as Streptococcus and Staphylococcus species, including methicillin-sensitive Staphylococcus aureus (MSSA).

Using intravenous ampicillin-sulbactam is particularly useful in patients who may require hospitalization or have more severe presentations of cellulitis since it provides a quicker and more effective way to ensure adequate drug levels in the bloodstream. The broad-spectrum activity of this combination covers both aerobic and anaerobic bacteria, enhancing its efficacy in treating skin and soft tissue infections.

While oral dicloxacillin is effective against MSSA, it may not be suitable for all patients, especially those with moderate to severe disease that necessitates intravenous therapy. Intravenous nafcillin, although it targets MSSA specifically, does not provide the same breadth of coverage against other potential pathogens as ampicillin-sulbactam does. Intravenous gentamicin is primarily an aminoglycoside effective against gram-negative organisms and is not a first-line treatment for cellulitis, where the primary pathogens are generally gram-positive.