Final answer:
The most common cause of cellulitis is Staphylococcus aureus, and initial treatment usually begins with oral antibiotics like dicloxacillin or first-generation cephalosporin. MRSA concerns may require alternative antibiotics such as clindamycin or TMP-SMX. Surgical intervention may be needed if the infection is severe, like necrotizing fasciitis.
Step-by-step explanation:
Most Common Pathogen in Cellulitis and Initial Treatment
The most common causative microorganism in cellulitis, especially when extending from a pustule on the hand to the axilla, is Staphylococcus aureus, often methicillin-susceptible. The initial treatment for such an infection traditionally involves antibiotic therapy, and the first line is typically oral antibiotics such as penicillinase-resistant penicillins (e.g., dicloxacillin) or first-generation cephalosporins. In cases where MRSA (methicillin-resistant Staphylococcus aureus) is a concern, options such as clindamycin, trimethoprim-sulfamethoxazole (TMP-SMX), or doxycycline may be used. It is crucial to monitor the patient's response to the treatment closely and adjust the antibiotic regimen accordingly based on culture and sensitivity results if the condition doesn't improve or worsens.
For patients who do not respond to initial antibiotic therapy or who display rapid progression, as seen in necrotizing fasciitis, aggressive surgical debridement of the infected tissue is often required in addition to broad-spectrum intravenous antibiotics to control the spread of the infection.