A Gram stain from a gum lesion showed amoebae. What is the correct identification from a trichrome smear showing amoebae with a single nucleus?

The presence of amoebae with a single nucleus found in a trichrome smear from a gum lesion aligns with the characteristics of Entamoeba gingivalis. This particular amoeba is often associated with oral lesions and can be present in the subgingival plaque or gingival tissues.

Entamoeba gingivalis is distinguished by its morphology, specifically having a single nucleus and being able to form trophozoites that are typically seen in the oral cavity. Its presence is often indicative of periodontal disease, highlighting the connection between oral health and parasitology.

In the context of the other choices, Trichomonas tenax, while also found in the oral cavity, is a flagellate and not an amoeba, which eliminates it as a possibility. Entamoeba histolytica and Entamoeba dispar are important for their role in intestinal disease and are typically identified in stool samples rather than from oral lesions. Entamoeba polecki primarily affects swine and is not commonly associated with human oral conditions. Therefore, the identification of only a single nucleus within amoebae in the context of a gum lesion strongly supports the classification as Entamoeba gingivalis.