Bacterial Conjunctivitis

Incidence

The incidence and prevalence of bacterial conjunctivitis is difficult to determine. Most cases are mild, self-limited, and patients do not seek medical attention. Yet conjunctivitis represents approximately 50% of ophthalmic conditions encountered in primary care and 30% of diagnoses in emergency room visits. ^,

Risk Factors

Infectious forms of conjunctivitis develop from exogenous contamination or a predominant organism from the ocular surface flora. Inoculation occurs from contaminated fingers, oculogenital spread, fomites, infection of adnexal structures, transmission from infected individuals, and iatrogenic or accidental trauma. Increased susceptibility occurs with compromise of the tear film, defects or inflammation of the epithelial barrier, exposure from lid abnormalities, giant fornix syndrome, immunosuppression, contact lens use, and age.

Categories of Bacterial Conjunctivitis

The presentation of bacterial conjunctivitis is a spectrum spanning both duration and severity. Most common is acute conjunctivitis, which is localized to the ocular surface and typically self-limited. In contrast, hyperacute and chronic presentations indicate a need for further evaluation and treatment.

Pathogens

The Antibiotic Resistance Monitoring in Ocular Microorganisms (ARMOR) surveillance study conducted on conjunctival isolates from 2009 to 2016 throughout the United States identified the most common bacterial pathogens ( Table 37.1 ). In children, Haemophilus influenzae is the predominant cause followed by Streptococcus pneumoniae , Staphylococcus aureus , and Staphylococcus epidermidis . In contrast, prevalent bacterial causes are reversed in adults, with the majority caused by S. aureus or coagulase negative S. epidermidis , followed by S. pneumoniae , H. influenzae , and Pseudomonas aeruginosa particularly in contact lens wearers.

Signs and Symptoms

Signs and symptoms significantly resemble those in viral conjunctivitis, particularly epidemic keratoconjunctivitis or pharyngoconjunctival fever. The overlap in clinical presentation is compared in Table 37.2 . Symptoms include sudden onset of irritation, redness, swelling, and eyelids that are “glued” together. Clinical findings include discharge ( Fig. 37.1 ), conjunctival papillae ( Fig. 37.2 ) and chemosis, and injection.

Certain bacterial species can present with more severe manifestations, including lymphadenopathy, follicles ( Fig. 37.3 ), membranes and pseudomembranes ( Fig. 37.4A and B ), subconjunctival hemorrhage, and cicatricial changes (see Table 37.1 ).

The interaction between pathogen and the host immune response can be detrimental to the ocular surface. Marginal infiltration, ulceration, and perforation can occur with Haemophilus aegyptius , Neisseria gonorrhoeae , Streptococcus pyogenes , and Moraxella. H. aegyptius also may cause phlyctenular keratoconjunctivitis. Corynebacterium diphtheriae may cause cicatricial changes from conjunctival necrosis resulting in xerosis, symblepharon, trichiasis, and entropion. The initial presentation of Chlamydia trachomatis can also cause severe inflammation; further details are described later in this chapter.

Associated Extraocular Manifestations

Certain species can also present with serious systemic infections. H. influenzae has nonencapsulated and encapsulated strains. The nonencapsulated strain is associated with an upper respiratory infection, and 25% of children may also have otitis media, while 18% of affected children can develop meningitis. The encapsulated strain produces a more severe course. Complications may include bacteremia, meningitis, septic arthritis, epiglottitis, and cellulitis. C. diphtheriae conjunctivitis rarely occurs after vaccination; however, when it does occur, toxins from diphtheria can paralyze extraocular muscles and accommodation, impair respiration, and cause cardiac toxicity. Children may have a preceding membranous pharyngitis. Treatment will require erythromycin as well as antitoxin therapy. H. aegyptius is highly contagious and can cause Brazilian purpuric fever, a fatal childhood illness that follows purulent conjunctivitis.