A positive Wood's light examination indicates which infection?

A positive Wood's light examination is specifically used to detect fungal infections, particularly those caused by certain dermatophytes. One of the most notable pathogens that may fluoresce under Wood's light is Microsporum canis, a common cause of tinea capitis (scalp ringworm), which often appears as a greenish-yellow fluorescence.

This technique is valuable in clinical dermatology as it helps differentiate fungal infections from other skin conditions. For instance, fungal elements such as those from Microsporum canis can emit specific light wavelengths upon exposure to Wood's lamp, which can aid in both diagnosis and the identification of potential carriers of infection.

In contrast, viral infections like herpes zoster typically do not show fluorescence during a Wood's light examination. Similarly, infections caused by Treponema pallidum (which leads to syphilis) are not identifiable by this method, as they do not fluoresce. Parasitic infestations, such as those caused by Pediculus humanus (lice), also lack the characteristic fluorescence observed with certain fungal infections.

Thus, a positive Wood's light examination is indicative of a mycotic infection, particularly one caused by Microsporum canis, making it the correct choice in this scenario.