Contributor:  Gordon K. Klintworth
Bacterial conjunctivitis is conjunctivitis caused by bacteria. Most examples of  this bacterial infection are caused by organisms that are part of the normal conjunctival flora; others are foreign to the ocular surface. Most conjunctival pathogens reach the conjunctiva from the tissue surface, but some of them are  part of a systemic disease in which the bacteria are acquired by an endogenous route, such as secondary syphilis [syphilis - secondary]). Causes of bacterial conjunctivitis include: Bartonella henselae [cat scratch disease]), Brucella [brucellosis], Corynebacterium diphtheriae [diphtheria], Neisseria gonorrhoeae [gonorrhea], Neisseria meningitidis, Haemophilus influenzae, Streptococcus sp. [streptococcal infection], Staphylococcus sp. [staphylococcal infection], Francisella tularensis, Mycobacterium tuberculosis [tuberculosis], Listeria monocytogenes [listeriosis], Haemophilus ducreyi, Yersinia sp, and Treponema pallidum [syphilis]. Streptococcus pneumoniae [pneumococcal infection] can cause conjunctivitis, especially in a temperate climate. Bacterial conjunctivitis is characterized by a markedly hyperemic conjunctiva that is typically covered by a thick purulent discharge and a diffuse papillary reaction of the tarsal conjunctiva. Bacteria are found both extracellularly and within neutrophils in a bacterial conjunctivitis. Most cases of bacterial conjunctivitis are self-limited. Some bacteria, such as Neisseria gonorrhoeae can invade an the intact conjunctival epithelium, others require a break in the surface epithelium to invade the underlying tissues. Certain bacteria infect not only the conjunctiva, but also the eyelids and cause chronic blepharoconjunctivitis [blepharoconjunctivitis - chronic]. Recurrent bacterial conjunctivitis  has been documented in patients with defective humoral immunity due to severe deficiencies of B-lymphocytes. Topical ophthalmic antibiotics and 8-methoxyfluoroquinolones (gatifloxacin, levofloxacin, and moxifloxacin) are used in the treatment of bacterial conjunctivitis.