Skin Infection Cellulitis Cellulitis is a spreading infection of the skin caused by bacteria.  The typical causal agents are two: the gram-positive bacteria Staphylococcus aureus ("staph") and Streptococcus ("Strep").  Other bacteria may also cause Cellulitis, such as the gram-negative Escherichia coli. Hot and red spreading rash Streaking may appear going toward the center of the body Swollen glands may or may not occur Fever Usually evident on examination Culture by saline injection and aspiration (rarely done) Antibiotics: Cephalexin (Keflex)Keflex) or Dicloxacillin by mouth in typical cases Cefazolin intravenously in severe cases Broad Spectrum antibiotics if gram-negative bacteria is suspected (especially diabetics) Venous stasis Erysipelas Deep Vein Thrombosis