What is the first-line treatment for cellulitis caused by Staphylococcus aureus?

Cellulitis caused by Staphylococcus aureus, particularly the methicillin-sensitive strain, is primarily treated with dicloxacillin, which is a penicillinase-resistant penicillin. This class of antibiotics is effective against penicillin-resistant strains of Staphylococcus aureus due to its structure that allows it to withstand the enzymatic degradation by beta-lactamase enzymes produced by the bacteria. Dicloxacillin is particularly well-suited for treating skin and soft tissue infections such as cellulitis because it achieves good tissue penetration, which is critical for treating infections that are localized within the skin and subcutaneous tissues.

In contrast, while cephalexin is also an option for cellulitis, it is typically reserved for cases where methicillin-resistant Staphylococcus aureus (MRSA) is not a concern, and it may not be as effective against specific strains as dicloxacillin. Amoxicillin is more effective against organisms like Streptococcus but does not have the same level of activity against Staphylococcus aureus. Vancomycin is often used for serious infections caused by MRSA but is generally not the first-line treatment for uncomplicated cellulitis caused by the methicillin-sensitive strain when effective alternatives like dicloxacillin are available