What infection is characterized by branching gram-positive rods with sulfur granules?

Actinomyces israelii is the organism responsible for infections characterized by branching gram-positive rods with sulfur granules. This bacterium is a part of the normal flora of the mouth and gastrointestinal tract. When it causes infection, it typically leads to actinomycosis, which often presents as a chronic suppurative infection. The appearance of sulfur granules, which are clusters of bacteria, is a distinctive feature observed in pus or exudate from affected tissues. These granules can be a notable finding in laboratory samples.

The branching filamentous nature of Actinomyces is also a key characteristic, which can be visually confirmed under a microscope. This kind of structural appearance is essential in differentiating it from other gram-positive rods that may not display such branching or the presence of sulfur granules. The specific environment of actinomycosis, often following a dental procedure or trauma, further supports the identification of Actinomyces israelii as the causative agent. Understanding these features is critical for accurate diagnosis and treatment.