Cellulitis (PO)
Cellulitis when not associated with abscess or purulence is more likely to be caused by group A streptococcus(GAS) or other streptococci (Group C and Group).
Cellulitis is commonly caused by GAS and Staphylococcus aureus. A non-purulent infection suggests streptococci are more likely to be the etiology. In the absence of SIRS, MRSA colonization, or penetrating trauma, options directed at GAS are appropriate including:
Penicillin VK (No S aureus coverage)
Cephalexin (Also covers MSSA)
Clindamycin (Also provides MSSA and MRSA coverage)
TMP/SMX is an option for suspected Staphylococcal skin and soft tissue infections but may be less effective for GAS.
References:
Stevens DL, Bisno AL, Chambers HF, Dellinger EP, Goldstein EJ, Gorbach SL, Hirschmann JV, Kaplan SL, Montoya JG, Wade JC; Infectious Diseases Society of America. Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the Infectious Diseases Society of America. Clin Infect Dis. 2014 Jul 15;59(2):e10-52. PMID: 24973422
Bruun T, Oppegaard O, Kittang BR, Mylvaganam H, Langeland N, Skrede S. Etiology of Cellulitis and Clinical Prediction of Streptococcal Disease: A Prospective Study. Open Forum Infect Dis. 2015;3(1):ofv181. Published 2015 Nov 25. https://pubmed.ncbi.nlm.nih.gov/26734653/