Objectives: Aetiological diagnosis of bacterial conjunctivitis by aerobic cultivation with identification and susceptibility test of the isolated bacteria and of viral conjunctivitis by direct antigen detection and cell culture.

Test material: Discharge from the eye(s).

Collection time: Before start of antibiotic therapy.

Equipment: Sterile cotton wool sponge, cotton tipped swab, test-tube with transport medium, clean microscope slide.

Procedure: 1. Pull down the lower eyelid so that the lower conjunctival fornix is exposed.

2. Swab the fornix without touching the rim of the eyelid with the sterile cotton swab.

3. Place the swab immediately in a bacterial or viral transport medium or, if the specimen is brought to the laboratory immediately, in a sterile test tube with 0.5 mL of buffered saline (pH 7).

Storage: Refrigerated (2-8 °C).

Transportation: Preferably send in a cooling box (2-8 °C).

Reporting: If suspicion of gonococcal infection in a newborn is suspected upon microscopic examination, the result should be conveyed to the treating physician immediately. All bacteria isolated in fair amounts and not resembling contaminants will be identified and tested for antibiotic susceptibility, including susceptibility to chloramphenicol. Culture results will be available in 1-2 days.

The main bacterial causes of conjunctivitis are pneumococci, Staphylococcus aureus, Haemophilus influenzae, Streptococcus pyogenes, Moraxella lacunata, gonococci, and enterobacteria. The main viral causes are adenovirus, picornavirus, measles, Molluscum contagiosum and Herpes simplex. The rim of the eyelids are heavily colonized with bacteria, so if the sample is not taken correctly, the culture result can be quite misleading. Common contaminants are coagulase-negative staphylococci, viridans streptococci, diphtheroids, nonpathogenic neisseriae, and Acinetobacter.

Comments: Bacterial conjunctivitis is characterized by a sticky mucopurulent discharge, whereas viral conjunctivitis has a watery discharge, pseudomembranes, follicles, petechial haemorrhages and superficial punctate keratitis.

Chlamydia trachomatis starts as a follicular conjunctivitis which may progress to punctate keratitis and occasionally to trachoma with follicles, papillae, and corneal pannus. Examination for Chlamydia is dealt with in the section "eye scraping for Chlamydia" (page 6970).

Neonatal conjunctivitis is caused by many organisms. The gonococcus is the most serious cause producing an acute conjunctivitis within the first few days of birth, which may be followed by corneal ulceration, scarring and eventually blindness. Chlamydia trachomatis produces a more mild conjunctivitis within the first 2 weeks of birth. Bacteria from the mother's birth canal may also infect the newborn child's conjunctiva. Nongenital bacteria such as Staphylococcus aureus and Streptococcus pyogenes may also cause conjunctivitis in the newborn.

Granulomatous conjunctivitis is a rare unilateral conjunctivitis with local inflammatory granuloma and regional lymphadenopathy. It has many aetiologies, e.g. tuberculosis, syphilis, tularaemia, actinomycosis, sporotrichosis, lymphogranuloma venereum, eye worms and fly larvae.

Viral conjunctivitis is mainly caused by herpes-, paramyxo-, and enterovirus.