What is the next best step for a patient with recurrent bilateral conjunctivitis who has failed treatment with Polytrim (polymyxin B and trimethoprim) and Ofloxacin (floxin) drops?

Recurrent Bilateral Conjunctivitis After Failed Polytrim and Ofloxacin

For recurrent bilateral conjunctivitis that has failed both Polytrim and ofloxacin, you must first determine the underlying etiology before selecting the next treatment, as bacterial resistance is unlikely and a non-bacterial cause (viral, chlamydial, or allergic) is the most probable explanation for treatment failure. 1

Critical Diagnostic Considerations Before Prescribing

Rule Out Vision-Threatening Conditions First

• Examine the cornea with fluorescein staining immediately to detect any corneal involvement, as this changes management entirely and may indicate HSV keratitis, adenoviral keratoconjunctivitis, or bacterial keratitis requiring more aggressive therapy 2
• Check for preauricular lymphadenopathy, which suggests viral (adenovirus, HSV) or chlamydial etiology rather than simple bacterial conjunctivitis 1
• Assess for follicles on the bulbar conjunctiva and semilunar fold, which is the distinctive sign of chlamydial conjunctivitis requiring systemic antibiotics, not topical therapy 1, 2

Why Bacterial Resistance Is Unlikely

The failure of two different antibiotic classes (Polytrim contains trimethoprim-polymyxin B; ofloxacin is a fluoroquinolone) makes simple bacterial conjunctivitis with resistance highly improbable 3, 4, 5. Mild bacterial conjunctivitis is self-limited and typically resolves spontaneously within 5-7 days even without treatment 1. If truly bacterial and severe enough to persist, you would expect response to at least one of these broad-spectrum agents.

Algorithmic Approach to Next Steps

If Follicular Conjunctivitis Present (Bulbar/Semilunar Fold Follicles)

Treat for chlamydial conjunctivitis with systemic antibiotics - topical therapy alone is inadequate 1:

• This requires oral azithromycin or doxycycline (see your local guidelines for dosing)
• Topical antibiotics provide no additional benefit 1
• Treat sexual contacts simultaneously and consider sexual abuse in children 1
• More than 50% of infants also have nasopharyngeal, genital, or pulmonary infection requiring systemic therapy 1

If Preauricular Lymphadenopathy + Watery Discharge

This is viral conjunctivitis (likely adenovirus), which requires supportive care only 1, 2:

• No antibiotic drops will help - this is self-limited, resolving in 5-14 days 1, 2
• Monitor for subepithelial infiltrates that may develop 1+ weeks after onset, which can cause vision loss 1
• If subepithelial infiltrates cause blurring/photophobia, consider topical corticosteroids (loteprednol or fluorometholone preferred to minimize IOP elevation) 1
• Highly contagious - counsel on infection control 1

If Unilateral or Bilateral with Vesicular Eyelid Lesions

Consider HSV conjunctivitis requiring antiviral therapy 1:

• Topical ganciclovir 0.15% gel 3-5 times daily (less toxic than trifluridine) 1
• Add oral antivirals (acyclovir 400mg 5x/day, valacyclovir 500mg 2-3x/day, or famciclovir 250mg 2x/day) as topical alone may be inadequate 1
• Never use topical corticosteroids - they potentiate HSV infection 1

If True Bacterial Conjunctivitis with Copious Purulent Discharge

For the rare case of genuine antibiotic-resistant bacterial conjunctivitis:

Switch to moxifloxacin 0.5% or gatifloxacin 0.3% - newer fluoroquinolones with broader gram-positive coverage than ofloxacin 6, 7:

• Moxifloxacin: 1 drop 3 times daily for 7 days 6
• Gatifloxacin: 1 drop every 2 hours while awake on day 1 (up to 8 times), then 2-4 times daily days 2-7 7

If MRSA is suspected (nursing home resident, recurrent infections, severe inflammation):

• MRSA is increasingly common and resistant to most fluoroquinolones 1
• Consider compounded vancomycin drops from a 503A/503B pharmacy 1
• Obtain cultures before switching therapy 1

Common Pitfalls to Avoid

• Do not prescribe another topical antibiotic without determining the actual etiology - you're likely treating the wrong condition 1
• Do not miss chlamydial conjunctivitis - it requires systemic therapy and has serious sequelae including corneal scarring and blindness if untreated 1
• Do not use topical steroids empirically - they worsen HSV infections and should only be used for specific indications like adenoviral subepithelial infiltrates 1
• Recurrent bilateral conjunctivitis warrants ophthalmology referral per AAO guidelines 1