Chapter 29 discusses skin and soft tissue infections, and that many different micro-organisms, including bacteria, fungi, and some viruses, may be involved in skin and soft-tissue infections. However, by far the commonest bacterial causes are Staph. aureus and Str. pyogenes . Thrush is usually caused by the yeast Candida albicans , and cold sores by the virus herpes simplex. It also covers impetigo, MRSA infections and PVL toxin, and necrotising fasciitis and toxic shock syndrome.