Bacteria are amazingly resilient organisms.
They have been evolving for billions of years and no part of the Earth has escaped the attention of these natural survivors. All plant and animal species are subject to their sometimes-deadly attention. Not all bacteria are harmful to humans however. The human body has evolved its own defensive strategy to fight serious bacterial infection - for most of the time our immune system is brilliant at coping with these microbes. Sometimes however, our immune system is overwhelmed in a ferocious bacterial attack.