Which of the following is NOT one of the diagnostic criteria for Ludwig's angina?

Ludwig's angina is characterized by bilateral swelling of the submandibular and sublingual areas, usually resulting from infections of the teeth or oral cavity. The presence of large amounts of visible pus in the submandibular space is not typically one of the diagnostic criteria. Instead, while pus may be present in severe cases, the focus is more on the clinical signs of swelling, edema, and the systemic symptoms associated with the infection.

Bilateral cellulitis is indeed a hallmark of Ludwig's angina, reflecting the nature of the infection spreading through submandibular spaces. The presence of gangrene can sometimes be observed in severe infections but is not a direct diagnostic criterion; it indicates a worse prognosis rather than a diagnostic feature. Sparing of glandular tissues is also an important characteristic, as Ludwig's angina usually does not directly involve the major salivary glands, which helps distinguish it from other types of infections in the head and neck region.

Thus, option A stands out as it does not align with the primary diagnostic criteria established for Ludwig's angina.