Which type of bacteria are regarded as harmless?

Non-pathogenic bacteria are indeed regarded as harmless. These bacteria do not cause disease in humans and are often beneficial to the body. For instance, many non-pathogenic bacteria exist naturally in our microbiome and play essential roles in digestion and bolstering the immune system. They can also be found in various environments, contributing to processes such as fermentation and nutrient cycling.

Pathogenic bacteria, on the other hand, are the ones responsible for causing diseases and infections. Infectious bacteria also refer to those that can lead to an illness, whereas chronic bacteria may imply those that cause long-lasting conditions or infections. Therefore, the distinction lies in the fact that non-pathogenic bacteria coexist peacefully with hosts and can often provide health benefits, while the others are associated with negative effects on health.