noun, plural: pathogens
Not all bacteria are pathogens, in fact most of them are harmless and only a few are pathogenic. Examples of pathogenic bacteria are Mycobacterium tuberculosis (causing tuberculosis), Streptococcus penumoniae (causing pneumonia), Shigella, Campylobacter and Salmonella (causing foodborne illnesses).
Word origin: from Greek pathos, suffering/emotion, and gene, to give birth to.
Related forms: pathogenic (adjective), pathogenesis (noun), pathogenous (adjective), pathogeny (noun).
Related phrases: opportunistic pathogen.