What is the correct identification for an anaerobic gram-positive diphtheroid with specific results collected from blood culture?

The identification of an anaerobic gram-positive diphtheroid from a blood culture that corresponds to the given characteristics points specifically to Propionibacterium acnes. This organism is known for its role in skin microbiota and its association with various infections, particularly in immunocompromised individuals or in cases of device-related infections.

Propionibacterium acnes is characterized by its anaerobic metabolism, producing propionic acid as a metabolic end product, which is a key feature in distinguishing it from other similar organisms. Its gram-positive nature and the diphtheroid-like morphology (short rods that may appear clumped or arranged together) are also significant.

In contrast, Eubacterium lentum, while also an anaerobic gram-positive organism, has distinct characteristics and a different clinical association. Actinomyces species usually appear as branched filamentous rods and are more commonly associated with actinomycosis. Peptostreptococcus species are cocci and do not fit the diphtheroid description. Therefore, the distinctive features of Propionibacterium acnes, including its diphtheroid characteristics, support its identification as the correct answer in this context.