All bacterial noted to be Non-Pathologic in Human Gut ,they are so because their structure and EXOCyTOTIC molecules are in symbiotic relationship with host or different specie ,therefore may not cause harm but could be dangerous to their host when their microbiota population overwhelm the system and the symbiotic relationship between otherwise different neighboring species or with the host is distorted ,or there is antibiotics genetic resistant that resulted from treatment of pathogenic organisms.Therefore arming once self with this information,there is no safe or good gut flora. except flora less virulent with gut symbiosis.