To identify the organism related to the blood smear image, we evaluate the features unique to each option in the context of pathology:
P. falciparum: This species of Plasmodium is known for causing malaria. In a blood smear, it is characterized by ring forms, trophozoites, schizonts, and gametocytes. The ring forms are often seen inside red blood cells, and a key identification feature is the presence of multiple ring forms in a single cell.
S. Typhi: This bacterium causes typhoid fever. It does not appear in blood smears as organisms but can cause leukopenia or anemia. The organism is typically diagnosed by blood culture, not smear.
Treponema pallidum: Causes syphilis. It is a spirochete bacterium and is not visible on standard blood smears, requiring dark field microscopy or specific staining techniques.
Toxoplasma gondii: This parasite causes toxoplasmosis and is generally not diagnosed via blood smear; rather, serological tests are used.
Given these characteristics, P. falciparum is the only organism identifiable via distinctive structures in a blood smear.
