Our digestive system is colonised by billions of bacteria and most of them are harmless. However, during times of stress, travel, illness, changes in the diet, and taking antibiotics, the unfriendly, pathogenic bacteria sometimes overwhelm the friendly bacteria. Pathogenic bacteria is the bacteria that causes bacterial infection. One of the bacterial diseases with highest disease burden is tuberculosis, which kills about 2 million people a year, mostly in certain areas of Africa. Pathogenic bacteria contribute to other globally important diseases, such as pneumonia, foodborne illnesses, tetanus, typhoid fever, syphilis, leprosy and diphtheria.
Beneficial bacteria is better identified as a probiotic and these are live bacteria that may confer a health benefit to the host. Bifidobacteria and lactic acid bacteria are the most common types of microbes used as probiotics and are commonly consumed as part of fermented foods with specially added active live cultures. These foods include yogurt, soy yogurt or dietary supplements.