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Acute Bacterial Conjunctivitis


Melvin I. Roat

, MD, FACS, Sidney Kimmel Medical College at Thomas Jefferson University

Last full review/revision Apr 2021| Content last modified Apr 2021

Acute conjunctivitis can be caused by numerous bacteria. Symptoms are hyperemia, lacrimation, irritation, and discharge. Diagnosis is clinical. Treatment is with topical antibiotics, augmented by systemic antibiotics in more serious cases.

Most bacterial conjunctivitis is acute; chronic bacterial conjunctivitis may be caused by Chlamydia and rarely Moraxella. Chlamydial conjunctivitis includes trachoma and adult inclusion conjunctivitis or neonatal inclusion conjunctivitis.

(See also Overview of Conjunctivitis.)

Etiology of Acute Bacterial Conjunctivitis

Bacterial conjunctivitis is usually caused by Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus species, Moraxella catarrhalis or, less commonly, Chlamydia trachomatis. Neisseria gonorrhoeae causes gonococcal conjunctivitis, which usually results from sexual contact with a person who has a genital infection.

Ophthalmia neonatorum (neonatal conjunctivitis) results from a maternal gonococcal and/or chlamydial infection. Neonatal conjunctivitis occurs in 20 to 40% of neonates delivered through an infected birth canal.

Symptoms and Signs of Acute Bacterial Conjunctivitis

Symptoms are typically unilateral but frequently spread to the opposite eye within a few days. Discharge is typically purulent.

The bulbar and tarsal conjunctivae are intensely hyperemic and edematous. Petechial subconjunctival hemorrhages, chemosis, photophobia, and an enlarged preauricular lymph node are typically absent. Eyelid edema is often moderate.

With adult gonococcal conjunctivitis, symptoms develop 12 to 48 hours after exposure. Severe eyelid edema, chemosis, and a profuse purulent exudate are typical. Rare complications include corneal ulceration, abscess, perforation, panophthalmitis, and blindness.

Ophthalmia neonatorum caused by gonococcal infection appears 2 to 5 days after delivery. With ophthalmia neonatorum caused by a chlamydial infection, symptoms appear within 5 to 14 days. Symptoms of both are bilateral, intense papillary conjunctivitis with eyelid edema, chemosis, and mucopurulent discharge.

Diagnosis of Acute Bacterial Conjunctivitis

  • Clinical evaluation
  • Sometimes culture of conjunctival smear or scrapings

Diagnosis of conjunctivitis and differentiation between bacterial, viral, and noninfectious conjunctivitis (see table Differentiating Features in Acute Conjunctivitis) are usually clinical. Smears and bacterial cultures should be done in patients with severe symptoms, immunocompromise, ineffective initial therapy, or a vulnerable eye (eg, after a corneal transplant, in exophthalmos due to Graves disease). Smears and conjunctival scrapings should be examined microscopically and stained with Gram stain to identify bacteria and stained with Giemsa stain to identify the characteristic epithelial cell basophilic cytoplasmic inclusion bodies of chlamydial conjunctivitis (see Adult Inclusion Conjunctivitis).

Differentiating Features in Acute Conjunctivitis


Discharge/Cell Type

Eyelid Edema

Node Involvement



Purulent/polymorphonuclear leukocytes


Usually none



Clear/mononuclear cells


Often present



Clear, mucoid, ropy/eosinophils

Moderate to severe


Mild to intense

Treatment of Acute Bacterial Conjunctivitis

  • Antibiotics (topical for all causes except gonococcal and chlamydial)

Bacterial conjunctivitis is very contagious, and standard infection control measures should be followed.

To avoid transmitting infection, physicians must

  • Use hand sanitizer or wash their hands properly (fully lather hands, scrub hands for at least 20 seconds, rinse well, and turn off the water using a paper towel)
  • Disinfect equipment after examining patients

Patients should do the following:

  • Use hand sanitizer and/or wash their hands thoroughly after touching their eyes or nasal secretions
  • Avoid touching the noninfected eye after touching the infected eye
  • Avoid sharing towels or pillows
  • Avoid swimming in pools

If neither gonococcal nor chlamydial infection is suspected, most clinicians treat presumptively with moxifloxacin 0.5% drops 3 times a day for 7 to 10 days or another fluoroquinolone or trimethoprim/polymyxin B 4 times a day. A poor clinical response after 2 or 3 days indicates that the cause is resistant bacteria, a virus, or an allergy. Culture and sensitivity studies should then be done (if not done previously); results direct subsequent treatment.

Because of antimicrobial resistance and because chlamydial genital infection is often present in patients with gonorrhea, adult gonococcal conjunctivitis requires dual therapy with a single dose of ceftriaxone 1 g IM plus azithromycin 1 g orally once (with azithromycin allergy or to treat expected chlamydial co-infection use doxycycline 100 mg orally twice a day for 7 days). Fluoroquinolones are no longer recommended because resistance is now widespread. Bacitracin 500 U/g or gentamicin 0.3% ophthalmic ointment instilled into the affected eye every 2 hours may be used in addition to systemic treatment. Sex partners should also be treated. Patients need to be evaluated for other sexually transmitted diseases and the local public health authorities (at least in the US) need to be notified.

Ophthalmia neonatorum is prevented by the routine use of silver nitrate eye drops (not available in the US) or erythromycin ointment at birth. Infections that develop despite this treatment require systemic treatment. For gonococcal infection, ceftriaxone 25 to 50 mg/kg IV or IM (not exceeding 125 mg) is given as a single dose. Chlamydial infection is treated with erythromycin 12.5 mg/kg orally or IV 4 times a day for 14 days. The parents should also be treated.

Key Points

  • Acute bacterial conjunctivitis tends to differ from viral conjunctivitis by the presence of purulent discharge and the absence of chemosis and preauricular adenopathy.
  • Forms of bacterial conjunctivitis that need to be treated differently include neonatal conjunctivitis, gonococcal conjunctivitis, trachoma, and inclusion conjunctivitis.
  • Diagnosis is usually clinical.
  • Treatment includes measures to prevent spread and antibiotics (topical, such as a fluoroquinolone, for causes except gonococcal and chlamydial).

Drugs Mentioned In This Article

Drug Name Select Trade
silver nitrate No US brand name
erythromycin ERY-TAB, ERYTHROCIN
azithromycin ZITHROMAX
moxifloxacin AVELOX
ceftriaxone ROCEPHIN
gentamicin GENOPTIC
Bacitracin BACIIM

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