Which of the following organisms is commonly tested using a skin scraping?

The organism Trichophyton is commonly tested using a skin scraping because it is a type of fungus responsible for various dermatological conditions, particularly those involving skin infections like tinea or ringworm. When diagnosing fungal infections, a skin scraping allows for direct examination and microscopic evaluation. This method reveals hyphae and spores characteristic of dermatophyte infections, which are crucial for accurate identification.

In contrast, the other organisms listed do not primarily require skin scrapings for diagnosis. Staphylococcus and Streptococcus are genera of bacteria typically isolated from blood, pus, or other bodily fluids rather than from skin scrapings. Escherichia coli is a bacterium commonly associated with gastrointestinal issues and is usually tested from stool samples rather than from the skin. Therefore, skin scraping is specifically correlated with the diagnosis of fungal infections, making Trichophyton the appropriate answer.