Recommended Eye Drop Antibiotic for Bacterial Conjunctivitis
For mild to moderate bacterial conjunctivitis, use moxifloxacin 0.5% ophthalmic solution, one drop three times daily for 7 days, as the first-line empiric broad-spectrum therapy. 1, 2, 3
Treatment Algorithm by Severity
Mild Bacterial Conjunctivitis
- Any broad-spectrum topical antibiotic is effective for mild cases, with choice based on convenience or cost, as no specific antibiotic has demonstrated superiority. 1
- Topical antibiotics provide earlier clinical and microbiological remission (days 2-5) compared to placebo and may reduce transmissibility, allowing earlier return to school for children. 1
- Alternative options include gentamicin, tetracycline, or ofloxacin topically. 1
- Povidone-iodine 1.25% ophthalmic solution may be considered when antibiotic access is limited. 1
Moderate to Severe Bacterial Conjunctivitis
- Moxifloxacin 0.5% three times daily for 7 days remains the recommended empiric therapy. 2, 3
- Obtain conjunctival cultures and Gram stain if gonococcal infection is suspected, as laboratory results will guide antibiotic selection. 1
- Gatifloxacin 0.5% is an alternative fourth-generation fluoroquinolone with superior gram-positive coverage compared to earlier generations. 4
- Besifloxacin 0.6% demonstrates better coverage against ciprofloxacin- and methicillin-resistant staphylococci than moxifloxacin. 2, 4
Critical Resistance Considerations
MRSA Conjunctivitis
- Switch to compounded topical vancomycin if MRSA is suspected, as fluoroquinolones (including moxifloxacin) are generally poorly effective against MRSA ocular isolates. 1, 2, 5, 4
- Methicillin resistance occurs in 42% of staphylococcal isolates with high concurrent fluoroquinolone resistance. 5, 4
- Obtain conjunctival cultures before starting treatment to guide appropriate antibiotic choice given increasing MRSA frequency. 1
Fluoroquinolone Resistance Risk Factors
- Recent fluoroquinolone use, recent hospitalization, advanced age, and recent ocular surgery increase resistance risk. 2, 5, 4
- A 20-year study showed increasing overall resistance to moxifloxacin from 1996 to 2015. 2, 5
Resistant Pseudomonas
Special Pathogen Considerations
Gonococcal Conjunctivitis
- Systemic antibiotic therapy is mandatory in addition to topical treatment, as topical therapy alone is insufficient. 1, 2, 5, 4
- Perform saline lavage to promote comfort and more rapid resolution. 1
- Add topical treatment as for bacterial keratitis if corneal involvement is present. 1
- See patients daily until resolution, performing interval history, visual acuity measurement, and slit-lamp biomicroscopy at each visit. 1, 2
- Refer patients and sexual contacts for evaluation of concomitant sexually transmitted diseases. 1
- Consider sexual abuse in children with gonococcal infection. 1
Chlamydial Conjunctivitis (Trachoma)
- Single-dose oral azithromycin is recommended, or topical azithromycin/tetracycline as alternatives. 1
- For neonatal chlamydial conjunctivitis, erythromycin achieves 96% clinical and 97% microbiological cure rates. 1, 4
- Systemic therapy is required, particularly in infants who may have infection at other sites. 2
Follow-Up Protocol
- Advise patients to return in 3-4 days if no improvement is noted. 1
- If no improvement after 7 days, reevaluate diagnosis and treatment. 5
- Perform visual acuity measurement and slit-lamp biomicroscopy at follow-up visits. 1
Important Caveats
Contact Lens Considerations
- Patients must discontinue contact lens wear if signs or symptoms of bacterial conjunctivitis are present. 3
FDA-Approved Indications
- Moxifloxacin 0.5% is FDA-approved for bacterial conjunctivitis caused by susceptible strains including Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae, and Chlamydia trachomatis. 3
- The standard dosing is one drop three times daily for 7 days. 3