What antibiotic treats bacterial eye infections?

Treatment of Bacterial Eye Infections

For bacterial conjunctivitis, use topical fluoroquinolones (moxifloxacin, gatifloxacin, or ofloxacin) or azithromycin 1.5% as first-line therapy for 5-7 days, as these provide superior efficacy and broad-spectrum coverage against common pathogens. 1, 2

Initial Treatment Approach

Topical antibiotics are recommended for all cases of bacterial conjunctivitis, even mild ones, as they reduce symptom duration, accelerate clinical and microbiological remission by days 2-5, reduce transmissibility, and allow earlier return to work or school. 1

Recommended First-Line Antibiotics

• Fluoroquinolones (moxifloxacin 0.5%, gatifloxacin, ofloxacin, or ciprofloxacin): Instill 1 drop in affected eye 3 times daily for 7 days 3
• Azithromycin 1.5%: Instill 1 drop twice daily for 3 days only - this shorter course achieves sustained tissue concentrations above MIC for 4 days in tears and 7 days in conjunctiva 4, 5
• Alternative options endorsed by WHO: Topical gentamicin, tetracycline, or ofloxacin 1, 2

When to Use Specific Antibiotics

Reserve fluoroquinolones for moderate to severe cases with copious purulent discharge, marked inflammation, pain, suspected resistant organisms, or contact lens wearers at higher risk for Pseudomonas infection. 2

For mild cases without these features, choose the most convenient or least expensive option (gentamicin, erythromycin, polymyxin B/trimethoprim), as no clinical evidence suggests superiority of any particular agent in uncomplicated cases. 2

Special Situations Requiring Systemic Antibiotics

Gonococcal Conjunctivitis

Topical antibiotics alone are insufficient - systemic therapy is mandatory: 6, 1

• Adults: Ceftriaxone 250 mg IM single dose PLUS azithromycin 1 g orally single dose 6
• Neonates: Ceftriaxone 25-50 mg/kg IV or IM single dose (not to exceed 125 mg) 6
• Add saline lavage to promote comfort and faster resolution of inflammation 6, 1

Chlamydial Conjunctivitis

Systemic antibiotics are required, especially in infants who may have infection at other sites; topical therapy provides no additional benefit: 6, 1

• Adults: Azithromycin 1 g orally single dose OR doxycycline 100 mg orally twice daily for 7 days 6
• Children ≥8 years: Same as adults 6
• Children <8 years weighing ≥45 kg: Azithromycin 1 g orally single dose 6
• Neonates: Erythromycin base or ethylsuccinate 50 mg/kg/day orally divided into 4 doses for 14 days 6

MRSA Infections

For methicillin-resistant Staphylococcus aureus infections, compounded topical vancomycin (15-50 mg/ml) may be required, as MRSA is resistant to most commercially available topical antibiotics including aminoglycosides. 1

Bacterial Keratitis (Corneal Infection)

For bacterial keratitis, use topical fluoroquinolones with loading doses every 5-15 minutes initially, then hourly, as they achieve better corneal tissue penetration and broader coverage than other agents. 2

Fortified antibiotics may be prepared for severe cases: 6

• Cefazolin 50 mg/ml or ceftazidime 50 mg/ml
• Tobramycin or gentamicin 14 mg/ml
• Vancomycin 15-50 mg/ml

Critical Follow-Up Parameters

Patients should return for follow-up if no improvement occurs after 3-4 days of treatment. 1, 2

Expected response timeline:

• Most patients show reduced discharge, pain, and lid edema within 24-48 hours 2
• If no improvement by 48 hours, consider switching to a fluoroquinolone or obtaining cultures 2

When to Obtain Cultures

For moderate to severe bacterial conjunctivitis, obtain conjunctival cultures and Gram staining before initiating treatment, especially if gonococcal infection is suspected. 1

Important Pitfalls and Caveats

• Never taper antibiotics below 3-4 times daily before completing the full course - subtherapeutic dosing increases antibiotic resistance risk 6
• Avoid prolonged use beyond 10 days - this can cause medication toxicity and corneal epithelial damage 2
• Do not prescribe antibiotics for viral conjunctivitis - this accounts for unnecessary costs and promotes resistance 2
• Contact lens wearers must discontinue lens wear during treatment and should not resume until infection has completely resolved 6
• Consider sexual abuse in children with gonococcal or chlamydial conjunctivitis 1

Referral to Ophthalmologist Required For:

• Visual loss
• Moderate or severe pain
• Severe purulent discharge
• Corneal involvement
• Conjunctival scarring
• Lack of response to therapy after 3-4 days
• Recurrent episodes 1, 2

Alternative for Resource-Limited Settings

Povidone-iodine 1.25% ophthalmic solution may be as effective as topical antibiotics and can be considered when access to antibiotics is limited. 1