Virulence Factors of Bacteria Related to Ocular Infections in Non Immunocompromised Patients: Review Article

Abstract

The ocular surface is constantly exposed to pathogenic bacteria. Many Gram positive and Gram negative bacteria have been implicated in ocular infections, in non immunocompromised patients, causing severe vision impairment. These microorganisms have in their quiver a variety of arrows to cause infection. The aim of this study is to list the virulence factors of the main ocular pathogens. Data were extracted from PubMed and Google Scholar. S. aureus and Streptococci, Bacillus cereus and Corynebacterium (non-diphtheriae) are the main culprits as far as Gram positive bacteria are concerned. S. aureus causes infections of the lacrimal apparatus, cornea and eyelids, conjunctivitis, keratitis, and endophthalmitis. Streptococcus pneumoniae, Streptococcus pyogenes, Enterococcus and Streptococcus viridians are isolated from post injection endophthalmitis cases. S. pneumoniae is most involved in keratitis, conjunctivitis, and endophthalmitis. Streptococcus pyogenes is most involved in blepharitis and hospital acquired conjunctivitis in neonates in the intensive care unit. Enterococcus faecalis is implicated in postoperative endophthalmitis cases. Corynebacterium (non-diphtheriae) species are involved mainly in infections complicating cataract surgery, keratoplasty, and vitrectomy. Bacillus species provoke conjunctivitis, keratitis and post-traumatic endophthalmitis. Bacillus cereus can cause rapidly destructive endophthalmitis. Among Gram negative bacteria, Neisseria gonorrhoeae, Pseudomonas aeruginosa, Chlamydia trachomatis, and Bartonella species are major ocular pathogens, responsible for severe ocular damage. Gonococcal conjunctivitis (GC) is still a cause of blindness in some developing countries. When it occurs in neonates, it is called gonococcal ophthalmia neonatorum. P. aeruginosa is related to contact lens-associated keratitis. Chlamydia trachomatis is the culprit of trachoma and inclusion conjunctivitis. Bartonella henselae causes bartonellosis or cat scratch disease, or cat scratch fever. Eye infection includes optic neuropathy and neuroretinitis. When the eye is the primary site of inoculation, the patients are diagnosed with Parinaud oculo-glandular syndrome (infection of the conjunctiva, eyelid and adjacent skin with regional lymphadenopathy). Chronic Bartonella infection provokes blurred vision, photophobia and eye irritation. Comprehension of the mechanism of infection, caused by these pathogens, is crucial in diagnosis and treatment.