In normal conditions, they do not cause any harm; but these bacteria can cause infection, if they gain entry into the body through any break in the skin. Apart from that, some physical and medical conditions, like diabetes, pregnancy, obesity, etc., are also considered as risk factors. Those with a weak immune system are also prone to develop this infection. Elderly people, and those with eczema, psoriasis, lymphedema, skin ulcer and HIV/AIDS, are vulnerable to this condition.