Streptococcus sp. bacteria (green) on the surface of a sand flea (Tunga penetrans), coloured scanning electron micrograph (SEM). The spherical (cocci) bacteria form long chains. The sand flea is a tropical parasite that burrows into the skin of its host (which can include humans) and feeds on its blood. Bacteria on the flea can often lead to the wounds becoming infected. Magnification: x1600 at 6x6cm size.