Our knowledge of the micro-organisms which produce pathologic conditions on the human conjunctiva, of their occurrence in various sections of the world and of the conditions necessary for their growth is becoming gradually more exact, although many points are still in dispute and await further accumulation of facts.
We know definitely that the same form of inflammation of the conjunctiva can be produced by various organisms. Examination of acute catarrhs, as well as of the purulent and pseudo-membranous forms of conjunctivitis, shows that cases which are clinically indistinguishable may contain bacteria that are morphologically very different. It is further definitely proven that one organism may produce various types of conjunctivitis, according to the conditions present and to the virulence of the organism, and that certain forms may exist in the conjunctiva at times without causing any reaction. Much, therefore, depends on the individual constitution or predisposition of the person affected
SHUMWAY EA. THE PATHOGENIC BACTERIA OF THE CONJUNCTIVA.. JAMA. 1906;XLVII(5):320-324. doi:10.1001/jama.1906.25210050004002a