How should bacterial conjunctivitis be treated in adults and neonates, including first‑line topical antibiotics and options for contact‑lens wearers or severe infection?

Treatment of Bacterial Conjunctivitis

For uncomplicated bacterial conjunctivitis in adults, prescribe a topical fluoroquinolone (moxifloxacin 0.5% or equivalent) three times daily for 5–7 days, which provides broad-spectrum coverage and accelerates clinical resolution. 1

First-Line Treatment for Adults

• Topical fluoroquinolones are the preferred first-line agents because they offer superior coverage against the three most common pathogens: Staphylococcus aureus, Streptococcus pneumoniae, and Haemophilus influenzae. 1
• Fourth-generation fluoroquinolones (moxifloxacin 0.5%, gatifloxacin) have enhanced gram-positive coverage, including activity against some methicillin-resistant S. aureus (MRSA) strains, compared to earlier generations. 1, 2
• No single antibiotic has demonstrated superiority for mild cases, so selection can be based on dosing convenience and cost—moxifloxacin's three-times-daily regimen improves adherence compared to four-times-daily alternatives. 1, 2
• The standard course is 5–7 days, which achieves clinical cure in 66–69% of patients by day 5–6 and microbiological eradication in 84–94% of cases. 1, 3

Alternative First-Line Options When Fluoroquinolones Are Unavailable

• Topical gentamicin, tetracycline, or ofloxacin 0.3% four times daily for 5–7 days are endorsed by the World Health Organization as acceptable alternatives. 1
• Polymyxin B/trimethoprim is effective for mild bacterial conjunctivitis but lacks Pseudomonas coverage. 1
• Povidone-iodine 1.25% ophthalmic solution may be as effective as topical antibiotics when antibiotic access is limited. 1, 2

Special Populations and Circumstances

Contact Lens Wearers

• Reserve fluoroquinolones (ofloxacin or ciprofloxacin) for contact lens wearers due to the significantly higher risk of Pseudomonas aeruginosa infection, which requires aggressive coverage. 1, 2
• Patients must discontinue contact lens wear during treatment and until symptoms fully resolve. 3

Suspected MRSA Infection

• MRSA isolates are generally resistant to fluoroquinolones and aminoglycosides but remain susceptible to vancomycin. 1, 2
• If no clinical improvement occurs within 48–72 hours of fluoroquinolone therapy, obtain conjunctival cultures and consider compounded topical vancomycin. 1, 2
• MRSA prevalence is rising in nursing home residents and community-acquired infections. 1

Severe Bacterial Conjunctivitis (Copious Purulent Discharge, Pain, Marked Inflammation)

• Obtain conjunctival cultures and Gram staining before initiating treatment, especially if gonococcal infection is suspected. 1, 2
• For severe cases, consider a loading dose: one drop every 5–15 minutes for the first hour, then hourly until clinical improvement, followed by standard three-times-daily dosing. 2

Mandatory Systemic Antibiotic Indications

Gonococcal Conjunctivitis

• Topical antibiotics alone are insufficient—systemic therapy is mandatory. 1, 2
• Adult regimen: Ceftriaxone 1 g IM single dose PLUS azithromycin 1 g orally single dose. 1, 2
• Add saline lavage to promote comfort and accelerate inflammation resolution. 1
• Daily monitoring is required until complete resolution to prevent corneal perforation, which can occur within 24 hours without treatment. 1, 2
• Obtain conjunctival cultures and Gram stain prior to treatment initiation. 1, 2

Chlamydial Conjunctivitis

• Systemic therapy is required—topical antibiotics provide no additional benefit. 1, 2
• Adult regimen: Azithromycin 1 g orally single dose OR doxycycline 100 mg orally twice daily for 7 days. 1, 2
• More than 50% of affected infants have concurrent infection at other sites (nasopharynx, genital tract, lungs), necessitating systemic coverage. 1, 2
• Re-evaluate after treatment completion, as failure rates approach 19%. 1, 2
• Screen for concurrent genital infections and treat sexual partners; consider sexual abuse in children. 1, 2

Treatment for Neonates (Birth to 28 Days)

Gonococcal Ophthalmia Neonatorum

• Neonatal regimen: Ceftriaxone 25–50 mg/kg IV or IM single dose (maximum 125 mg) PLUS topical antibiotics and saline lavage. 2, 4
• Admit for observation and arrange daily ophthalmology follow-up until complete resolution. 2, 4
• Clinical presentation includes marked eyelid edema, profuse purulent discharge, and rapid progression within 24–48 hours after birth. 2

Chlamydial Ophthalmia Neonatorum

• Neonatal regimen: Erythromycin base or ethylsuccinate 50 mg/kg/day orally divided into four doses for 14 days. 1, 2, 4
• Topical antibiotics alone are inadequate—systemic therapy is mandatory. 1, 2, 4
• Clinical cure rate is 80% by day 9; re-evaluation after the 14-day course is mandatory, and a second course may be needed if eradication is not confirmed. 1, 2
• Monitor for infantile hypertrophic pyloric stenosis in infants younger than 6 weeks receiving erythromycin. 2
• Onset typically occurs 5–12 days after birth with milder purulent discharge than gonococcal infection. 2

Maternal and Partner Management

• The mother and her sexual partners must be evaluated and treated according to adult STD treatment guidelines for both gonococcal and chlamydial neonatal conjunctivitis. 2

Treatment for Children (1 Month to 18 Years)

• Topical fluoroquinolones are first-line for children older than 12 months: moxifloxacin, levofloxacin, gatifloxacin, ciprofloxacin, or besifloxacin four times daily for 5–7 days. 2, 4
• A three-times-daily regimen (e.g., moxifloxacin) improves adherence in young children. 2
• Instruct parents to return for evaluation in 3–4 days if no improvement is noted, as lack of response may indicate resistant organisms or an alternative diagnosis. 2, 4
• Children can generally return to school 24 hours after initiating treatment once symptoms begin to improve. 4

Follow-Up Strategy and Expected Outcomes

• Advise patients to return in 3–4 days if no improvement is observed. 1, 2
• Signs of positive response include reduced pain and discharge, decreased eyelid edema or conjunctival injection, and sharper demarcation of any infiltrate perimeter. 1, 2
• At follow-up, perform interval history, visual acuity measurement, and slit-lamp biomicroscopy. 1, 2
• Approximately 64% of mild bacterial conjunctivitis cases in immunocompetent patients resolve spontaneously by days 6–10 without treatment, but topical antibiotics shorten symptom duration (62% cured by days 3–5 with antibiotics vs. 28% with placebo) and reduce transmissibility. 2, 5

Red-Flag Findings Requiring Immediate Ophthalmology Referral

• Visual loss or significant change in vision 1, 2
• Moderate to severe eye pain (beyond mild irritation) 1, 2
• Severe purulent discharge suggestive of gonococcal infection 1, 2
• Corneal involvement (opacity, infiltrate, or ulcer) 1, 2
• Conjunctival scarring 1, 2
• Lack of clinical response after 3–4 days of appropriate therapy 1, 2
• History of herpes simplex virus eye disease 1, 2
• Immunocompromised state 1, 2
• Recurrent episodes 1, 2

Critical Pitfalls to Avoid

• Never use topical corticosteroids (e.g., Tobradex) unless viral conjunctivitis—especially HSV and adenovirus—has been definitively excluded, as steroids potentiate viral replication, prolong adenoviral infections, and can cause corneal perforation in HSV. 1, 2
• Do not prescribe topical antibiotics for viral conjunctivitis, which accounts for unnecessary costs, promotes resistance, and provides no clinical benefit. 1, 2
• Oral antibiotics (e.g., Augmentin) are NOT indicated for routine bacterial conjunctivitis—they cannot achieve therapeutic levels in the conjunctiva and are reserved exclusively for gonococcal and chlamydial infections. 2
• Do not taper topical antibiotics below three to four times daily, as subtherapeutic doses increase the risk of antibiotic resistance. 1
• Prolonged antibiotic use beyond 7 days can cause ocular toxicity and should be avoided unless a specific indication exists. 1, 2

Infection Control Measures

• Strict hand hygiene with soap and water is critical to prevent transmission. 1, 2
• Advise patients to avoid eye rubbing, use separate towels, and avoid close contact during the contagious period. 1, 2
• Discard multiple-dose eyedrop containers after treatment to avoid cross-contamination. 2

Antimicrobial Resistance Considerations

• Fluoroquinolone resistance among Staphylococcus isolates is reported in 42% of regions surveyed, and Pseudomonas aeruginosa resistance to moxifloxacin has increased from 19% to 52% in some areas. 1, 2
• Individual risk factors for fluoroquinolone resistance include recent fluoroquinolone use, hospitalization, advanced age, and recent ocular surgery. 2
• In neonatal intensive care settings, gram-negative conjunctivitis is often resistant to gentamicin, particularly in low birth weight or low gestational age infants. 1