Bacterial Conjunctivitis (Pink Eye)

What is Bacterial Conjunctivitis?

Bacterial conjunctivitis, commonly called “pink eye,” is an inflammation of the conjunctiva—the thin, transparent membrane that covers the white part of the eye (sclera) and the inner surface of the eyelids. The infection is caused by bacteria that invade this delicate tissue, leading to redness, swelling, and a discharge that can be purulent (pus‑filled). While it can affect one eye, it frequently spreads to both eyes and is highly contagious, especially in close‑contact settings such as schools or day‑care centers.

Most episodes are mild and resolve with proper treatment, but untreated cases can lead to corneal complications and spread to others. Recognizing the condition early and following evidence‑based management helps prevent complications and limits transmission.

Common Causes

Bacterial conjunctivitis can arise from a variety of organisms and risk factors. The most frequent causative agents and contributing conditions include:

• Staphylococcus aureus – the leading cause in adults, often linked to skin flora.
• Streptococcus pneumoniae – common in children; may follow upper‑respiratory infections.
• Haemophilus influenzae (non‑typeable) – another pediatric culprit, especially in crowded settings.
• Morbilliform (Moraxella) catarrhalis – can cause chronic or recurrent infections.
• Neisseria gonorrhoeae – a rare but serious cause; usually associated with sexually transmitted infection.
• Chlamydia trachomatis – produces a more persistent, “inclusion” conjunctivitis, often in newborns or sexually active adults.
• Contact lens wear – improper hygiene or overnight wear can introduce bacteria.
• Eye trauma or foreign bodies – break the protective barrier and allow bacterial entry.
• Upper‑respiratory infections – bacterial sinusitis or pharyngitis can spread to the conjunctiva via the nasolacrimal duct.
• Reduced immunity – conditions such as diabetes, HIV, or immunosuppressive therapy increase susceptibility.

Associated Symptoms

Patients with bacterial conjunctivitis usually experience a pattern of eye‑related signs that help differentiate it from viral or allergic forms.

• Redness – diffuse or localized to the affected eye(s).
• Purulent discharge – thick, yellow‑green or white mucus that may cause the eyelids to stick together, especially after sleep.
• Crusting – especially on the lid margins in the morning.
• Foreign‑body sensation – a feeling that something is in the eye, often prompting frequent blinking.
• Tearing (epiphora) – excessive watery discharge alongside the pus.
• Itching or mild burning – less intense than in allergic conjunctivitis.
• Swelling of the eyelids (eyelid edema).
• Photophobia – mild sensitivity to bright light.
• Possible accompanying cold‑like symptoms – such as nasal congestion if the infection spread from the respiratory tract.

When to See a Doctor

Most cases of bacterial conjunctivitis improve with topical antibiotics, but certain situations warrant prompt professional evaluation:

• Symptoms persist longer than 7–10 days despite treatment.
• Severe pain, significant swelling, or inability to open the eye.
• Sudden loss of vision or blurring that does not improve.
• Intense redness confined to the inner corner (possible involvement of the cornea—keratitis).
• History of recent sexually transmitted infections (concern for gonococcal or chlamydial conjunctivitis).
• Infants under 1 month of age with any eye discharge (risk of serious neonatal infection).
• Contact lens wearers with redness and pain (risk of contact‑lens‑associated keratitis).
• Systemic symptoms such as fever, headache, or ear pain that suggest a broader infection.

Diagnosis

Diagnosis of bacterial conjunctivitis is primarily clinical, supported by a focused history and eye exam. The typical steps include:

1. History taking – onset, duration, discharge characteristics, exposure to sick contacts, contact‑lens use, trauma, and systemic illness.
2. Visual acuity check – to ensure the infection has not affected vision.
3. External eye inspection – using a torch or slit‑lamp to evaluate redness, swelling, and discharge.
4. Fluorescein staining – to detect corneal epithelial defects; a clear cornea suggests conjunctivitis only.
5. Culture or Gram stain (select cases) – indicated for severe, recurrent, or atypical presentations (e.g., suspected gonococcal infection).
6. Assessment for co‑existing conditions – such as allergic disease, dry eye, or blepharitis.

When the diagnosis is uncertain, especially in adults with purulent discharge and severe symptoms, a conjunctival swab for bacterial culture helps guide targeted antibiotic therapy.

Treatment Options

Effective management combines medical therapy with supportive home care. The choice depends on severity, patient age, and bacterial etiology.

Medical Treatments

• Topical antibiotic eye drops or ointments
  • First‑line agents: erythromycin ophthalmic ointment, trimethoprim‑polymyxin B drops, or fluoroquinolone drops (e.g., ciprofloxacin, ofloxacin) for contact‑lens wearers.
  • Duration: typically 5–7 days; many formularies advise a 5‑day course for uncomplicated cases.
• Oral antibiotics – reserved for severe infections, systemic involvement, or specific pathogens (e.g., Neisseria gonorrhoeae requires ceftriaxone 500 mg IM once).
• Corticosteroid eye drops – generally avoided in pure bacterial conjunctivitis but may be added by specialists if there is significant inflammation after the infection is controlled.

Home and Supportive Care

• Cold compresses – apply a clean, cold, damp washcloth for 5–10 minutes, 3–4 times daily to relieve discomfort.
• Gentle eyelid hygiene – use a cotton swab soaked in sterile saline or warm water to remove crusted discharge; always use a clean side for each eye.
• Avoid rubbing the eyes – reduces mechanical spread of bacteria.
• Artificial tears (preservative‑free) – help flush out irritants and keep the ocular surface moist.
• Hand hygiene – wash hands with soap and water before and after touching the eyes or applying medication.
• Discard contaminated eye products – replace eye makeup, contact‑lens solutions, and any eye drops opened >30 days ago.

Prevention Tips

The contagious nature of bacterial conjunctivitis means that simple habits can dramatically lower the risk of acquisition and spread:

• Wash hands thoroughly with soap for at least 20 seconds, especially after touching the face or eyes.
• Avoid sharing towels, pillowcases, eye cosmetics, or contact‑lens cases.
• Disinfect surfaces (door handles, phone screens) with an EPA‑approved disinfectant daily in households with a case.
• For contact‑lens wearers, follow the “clean, replace, store” routine and never sleep in lenses not approved for overnight wear.
• Replace eye makeup every 3 months and discard any product that may have been contaminated.
• Keep children’s toys and classroom materials clean; encourage regular hand‑washing breaks.
• If you or a child develop symptoms, stay home from school or work until 24 hours after starting antibiotic drops (or as advised by a clinician).
• Avoid swimming in pools or hot tubs while the infection is active, as chlorinated water can irritate the eye further.

Emergency Warning Signs

References

• Mayo Clinic. “Conjunctivitis (pink eye).” https://www.mayoclinic.org
• Cleveland Clinic. “Bacterial Conjunctivitis.” https://my.clevelandclinic.org
• Centers for Disease Control and Prevention. “Conjunctivitis (Pink Eye).” https://www.cdc.gov
• National Eye Institute (NIH). “Conjunctivitis.” https://www.nei.nih.gov
• World Health Organization. “Prevention of eye infections.” https://www.who.int
• American Academy of Ophthalmology. “Bacterial Conjunctivitis: Diagnosis and Management.” https://www.aao.org