Systemic Antibiotics in Bacterial Keratitis
Systemic antibiotics are rarely needed for bacterial keratitis and should be reserved for specific severe circumstances: when infection extends to adjacent tissues (e.g., sclera), when corneal perforation is impending or present, or in cases of gonococcal keratitis. 1
Primary Treatment Approach
The cornerstone of bacterial keratitis management is topical antibiotic therapy, not systemic antibiotics. 2, 3 The rationale is straightforward:
- Topical application is the most effective route for delivering antibiotics to the cornea, achieving high local concentrations that systemic therapy cannot match 2
- All commonly prescribed topical antibiotics show comparable effectiveness for bacterial keratitis 3
- Treatment success, time to cure, and serious complications are similar across different topical antibiotic regimens 4
When to Consider Systemic Antibiotics
Mandatory Indications
- Gonococcal keratitis: Systemic therapy is necessary in all cases 1
Severe Disease Considerations
Systemic antibiotics may be considered when: 1
- The infectious process has extended beyond the cornea to adjacent tissues (particularly scleral involvement)
- Impending corneal perforation is present
- Frank perforation of the cornea has occurred
Clinical Decision Algorithm
For typical bacterial keratitis:
- Start with intensive topical antibiotics (fluoroquinolone monotherapy or fortified combination therapy) 1
- Monitor daily for severe cases (deep stromal involvement, infiltrates >2mm, extensive suppuration) 1
- Do not add systemic antibiotics unless one of the specific indications above develops
For severe presentations:
- Assess for scleral extension on examination 1
- Evaluate corneal integrity for impending or actual perforation 1
- If gonococcal etiology suspected (rapid progression, copious purulent discharge), initiate systemic therapy immediately 1
Important Caveats
Recurrent staphylococcal keratitis presents a special scenario where systemic decolonization strategies (not treatment antibiotics) may be considered to prevent future infections, as S. aureus colonization of the nasopharynx, oropharynx, and ocular surface can serve as a reservoir. 1
Resistance patterns are evolving, with methicillin-resistant S. aureus showing >30% fluoroquinolone resistance and P. aeruginosa developing multidrug resistance. 5, 6 However, this affects topical antibiotic selection, not the decision to use systemic therapy.
The 2024 American Academy of Ophthalmology guidelines explicitly state that systemic antibiotics are "rarely needed" in bacterial keratitis, reinforcing that topical therapy remains the standard of care for the vast majority of cases. 1