What we know about endogenous endophthalmitis
A patient with endogenous endophthalmitis usually exhibits several ocular symptoms: decreased vision, redness, floaters, headache, and eye discharge.2,4 Systemic symptoms often occur 3 to 7 days after the onset of ocular symptoms; only half of all cases report prior systemic symptoms.
Associated conditions to consider
Endogenous endophthalmitis has been associated with long-standing medical conditions such as diabetes mellitus and chronic renal failure.4-6 In 40% of cases, endocarditis is the source of bacteremia.2,4 Other possible sources are meningitis, urinary tract infection, intra-abdominal abscess, cellulitis, IV drug abuse, and septic arthritis;7 invasive medical procedures such as gastrointestinal endoscopy;8 and abdominal surgery.4,9 According to our literature review, only 6 cases have been reported with pneumonia as the primary source of bacteremia.4,5,10
Likely causative organisms
Endophthalmitis is a clinical diagnosis confirmed by positive culture results on aqueous or vitreous samples. However, a negative result does not exclude the diagnosis. As per Okada et al,4 causative organisms were isolated from either vitreous or blood samples in 96% of their cases.
Fungal organisms account for more than 50% of all cases of endogenous endophthalmitis (TABLE). Candida albicans is, by far, the most frequent cause of fungal endophthalmitis, and aspergillosis is the second most common cause.
Bacterial endogenous endophthalmitis most often occurs with gram-positive organisms. However, an East Asian study by Wong et al11 showed gram-negative organisms in 70% of cases, with Klebsiella pneumoniae alone being responsible in 60% of the cases. Endophthalmitis caused by S pneumoniae usually has a poor prognosis.12
Ultrasound imaging of the eye (B-scan) usually shows increased echogenicity of the vitreous due to inflammation—a useful diagnostic indicator when the view of the vitreous is obscured by anterior chamber abnormalities. (This test was unavailable for our case.)
TABLE
Endogenous endophthalmitis: Which organisms to suspect, and when4,9,11,15
| Organism | Sources of infection |
|---|---|
| Gram-positive | |
| Staphylococcus aureus | Endocarditis, skin infections |
| Streptococcus pneumoniae | Endocarditis, pneumonia, meningitis |
| Streptococcus milleri | Endocarditis, liver abscess |
| Group B Streptococcus | Endocarditis |
| Clostridium species | GI tract abscess, procedures, carcinomas |
| Bacillus cereus | IV drug use |
| Gram-negative | |
| Pseudomonas aeruginosa | Abdominal abscess |
| Neisseria meningitides | Meningitis |
| Escherichia coli | Urinary tract or hepatobiliary system |
| Klebsiella pneumoniae | Urinary tract or hepatobiliary system |
| Fungal | |
| Candida albicans | Immunosuppression, diabetes mellitus, GI surgery, hyperalimentation |
| Aspergillosis | IV drug use, cardiac surgery, organ transplant |
| GI, gastrointestinal; IV, intravenous | |
Doing the most to preserve vision
Preserving a patient’s vision depends on prompt identification of the causative organism with blood and intravitreal cultures, and on appropriate therapy, including IV and intravitreal administration of antibiotics. Vitreal surgery is also a consideration. No randomized control trial has studied endogenous endophthalmitis management, due to the small number of cases worldwide. In managing endogenous endophthalmitis, most experts follow the outcome of the Endophthalmitis Vitrectomy Study (EVS),13 in which immediate vitrectomy and IV antibiotics were used to treat postoperative bacterial endophthalmitis.
Notable points from EVS, and a caveat. EVS enrolled 420 patients who had clinical evidence of endophthalmitis 6 weeks after cataract surgery or secondary to intraocular lens implantation, randomly assigning them in a 2×2 factorial design to study groups: vitrectomy vs vitreous tap, and systemic antibiotics vs no systemic antibiotics. All patients received intravitreal antibiotics. The systemic antibiotics used were ceftazidime and amikacin. There was no difference in final visual acuity between the vitrectomy and vitreous tap groups, except in patients who presented with the worst vision (light perception only). For these patients, vitrectomy significantly decreased the chance of severe visual loss to 20%, vs 47% in the vitreous tap group. The EVS also concluded that omitting systemic antibiotics does not compromise outcomes, and can reduce toxic effects, cost, and length of hospital stay.
An important qualifier of the EVS report is that the study enrolled patients with exogenous endophthalmitis; no patients with endogenous endophthalmitis were included. Moreover, systemic antibiotics used in EVS mainly covered gram-negative agents, even though gram-positive cocci were responsible for 94% of the cases.
Considerations in antibiotic selection. Vancomycin plus ceftazidime or fluoroquinolones are commonly used empirically for all forms of endophthalmitis until vitreous culture results are available. Fourth-generation fluoroquinolones (moxifloxacin and gatifloxacin) have increased potency against gram-positive bacteria compared with levofloxacin, while maintaining similar potency against gram-negative bacteria. Moxifloxacin has significantly greater ocular penetration and better gram-positive potency than gatifloxacin.14
Patients with endogenous endophthalmitis receive long-term IV antibiotics to treat the focus of systemic infection. As noted earlier, this patient completed a 6-week course of IV ceftriaxone and 2 weeks of oral moxifloxacin.
Even prompt action may not be enough
Red eye is common in outpatient settings. Endogenous endophthalmitis may be an uncommon cause of red eye, but you should consider it when a patient also has blurry vision and systemic symptoms. In this instance, it was an unusual complication of community-acquired pneumonia, which is also commonly seen in primary care. Treatment necessarily includes systemic and intravitreal antibiotics with or without vitrectomy. Immediate ophthalmologic referral is critical to preserving vision.