Do patients with Serratia marcescens, especially those with recent eye surgery, trauma, or compromised immune systems, need endophthalmitis screening?

Serratia marcescens and Endophthalmitis Screening

Yes, patients with Serratia marcescens bacteremia or systemic infection, particularly those with recent eye surgery, ocular trauma, or injection drug use, absolutely require urgent endophthalmitis screening with dilated fundoscopic examination by an ophthalmologist.

Clinical Context and Risk Assessment

Serratia marcescens is a recognized causative organism of endophthalmitis that can occur through multiple mechanisms 1:

• Post-surgical endophthalmitis: Following cataract surgery, trabeculectomy, penetrating keratoplasty, scleral buckle procedures, or glaucoma drainage implant placement 2, 3
• Endogenous (hematogenous) endophthalmitis: Via bloodstream seeding across the blood-eye barrier, particularly in patients with bacteremia and injection drug use 1, 4
• Post-traumatic: Through direct inoculation following penetrating ocular trauma 1

Who Needs Screening

Immediate ophthalmologic evaluation is mandatory for:

• Any patient with S. marcescens bacteremia, especially those with a history of injection drug use 4
• Patients within 6 weeks of any intraocular surgery who develop systemic S. marcescens infection 2, 3, 5
• Patients with ocular symptoms (pain, vision loss, hypopyon) and S. marcescens isolated from any source 2, 6
• Patients with S. marcescens endocarditis, as septic emboli can seed the eye 4

Diagnostic Approach

The screening examination must include 7:

• Direct dilated fundoscopic examination by an ophthalmologist
• If endophthalmitis is suspected clinically, obtain vitreous or aqueous humor culture via diagnostic tap before initiating treatment 7
• Blood cultures if systemic infection is suspected 4, 5

Critical Prognostic Considerations

S. marcescens endophthalmitis carries an exceptionally poor prognosis that distinguishes it from other bacterial causes 2, 3:

• 60% of patients achieve no light perception (complete blindness) in the affected eye 2
• Only 40% achieve visual acuity of 20/400 or better 3
• Persistent positive cultures occur in 10-50% of cases despite appropriate initial antibiotic therapy 2, 3
• High rates of enucleation or evisceration (40% in some series) 3

Treatment Implications

All S. marcescens isolates are resistant to vancomycin but universally sensitive to aminoglycosides (gentamicin), ceftazidime, fluoroquinolones (levofloxacin, ciprofloxacin), and carbapenems (imipenem) 2, 6. This antibiotic susceptibility pattern makes early identification critical, as empiric vancomycin-based regimens will fail.

Common Pitfalls

• Do not dismiss ocular symptoms in patients with S. marcescens bacteremia: Even subtle vision changes warrant immediate ophthalmologic consultation 4
• Do not delay screening in post-surgical patients: S. marcescens endophthalmitis can progress rapidly to irreversible vision loss 2, 5
• Do not assume initial treatment success: Repeat cultures may be necessary given the high rate of persistent infection 2, 3
• Recognize the association with injection drug use: Patients may have concurrent endocarditis, septic emboli to multiple organs, and disseminated infection requiring comprehensive evaluation 4