detectable on examination as fluctuance Acute bacterial adenitis is most often caused by group A β-hemolytic Streptococcus or Staphylococcus aureus (including methicillinresistant S aureus [MRSA]) Prompt initiation of oral antimicrobial therapy that empirically covers MRSA can prevent progression to a suppurative infection However, patients who have failed to improve with oral antimicrobial therapy or those who present with signs of toxicity require parenteral therapy Drainage of the suppurative nodes is sometimes required, even in appropriately treated cases ( Figs 47.3 and 47.4 )