Bacterial skin infection. Coloured scanning electron micrograph (SEM) of secondary bacterial skin infection in athletes foot. Athlete's foot, known medically as tinea pedis, is a common skin infection of the feet caused by fungus. The vesiculobullous type of athlete's foot is characterized by a sudden outbreak of itchy blisters and vesicles on the sole of the foot. This type on infection is often complicated by secondary bacterial infection by Streptococcus pyogenes, Staphylococcus aureus and other bacteria. Purple skin cells underly a variety of bacteria species (red) in this image. Magnification: x 2000 when printed at 10cm wide.