The healthy organism is always beset with a multitude of non-pathogenic bacteria.
No sharp line can be drawn between pathogenic and non-pathogenic Pathogenic bacteria.
pathogenic path·o·gen·ic (pāth'ə-jěn'ĭk) or path·o·ge·net·ic (-jə-nět'ĭk)
Having the capability to cause disease.
Relating to pathogenesis.
A descriptive term for a thing or condition that can cause disease.