Horse to human: Streptococcus equi septicemia presenting as endogenous endophthalmitis

Purpose To present a rarely reported systemic infection with streptococcus equi subspecies zooepidemicus (streptococcus equi), transmitted from a horse, and to describe successful treatment when complicated by endogenous endophthalmitis. Observations We diagnosed suspected streptococcus equi septicemia presenting as loss of vision in the right eye of an otherwise healthy polo player/horse trainer. He received immediate intravenous antibiotics and three vitrectomies with two intravitreal antibiotic injections during the first week, to cure infection and subsequent retinal detachment. Blood and initial vitreous cultures rapidly grew streptococcus equi. The septicemia was quickly controlled by systemic antibiotics without developing commonly seen and often fatal meningitis. The right eye recovered 20/30 visual acuity three months post infection. Conclusions Presentation of this rare septicemia as endogenous endophthalmitis illustrates the potentially lifesaving role of early diagnosis by the ophthalmologist. Immediate and recurrent vitrectomy in conjunction with intravitreal and systemic antibiotic therapy resulted in recovery of near normal vision, whereas less timely and interventional treatments have failed heretofore.


Introduction
2][3] Streptococcus equi is usually transmitted through contact with the nasal discharge of an infected horse.Human infection is associated with close contact with horses and consumption of unpasteurized dairy products. 2,4A commensal organism in horses, in humans it typically causes fulminant septicemia with severe complications, most notably meningitis, with a mortality rate of over 20 %. 1 After a literature review on October 21, 2023, using search engines PubMed and Google Scholar and key words "streptococcus equi" and "endogenous endophthalmitis," we found only three cases of endogenous endophthalmitis secondary to streptococcus equi septicemia. 3,5,6ne of these case reports described vision loss as the primary presenting symptom, and no treated eye regained useful vision.
We present a case of streptococcus equi septicemia with a primary presenting symptom of vision loss.Endogenous endophthalmitis from streptococcus equi septicemia was promptly diagnosed and treated, forestalling-life threatening sequalae and leading to successful recovery of vision.

Case report
A 48-year-old man, previously in good health, came to our retina clinic in no acute distress, after experiencing four days of spontaneous, painless loss of vision in the right eye.He had no history of ocular trauma, operative procedure, or prior eye disease.On the second day of symptoms, two days prior to presentation to our clinic, the patient experienced a marked decrease in vision, and he was seen by an ophthalmologist who initiated a diagnostic work up for sterile uveitis and began treatment with topical cycloplegics and steroids.Of note, the patient reported that he lived on a farm where he cared for polo horses and was himself a polo player.
On examination, the right eye had only light perception visual acuity.There was no conjunctival injection, a clear cornea, modest cell and flare, and a 2 mm hypopyon.Purulent vitreous infiltrate was visible abutting the entire posterior capsule of the clear crystalline lens, with a 9 mm pupil already pharmacologically dilated (Fig. 1), with no red reflex.Ultrasonography revealed homogeneous, modest strength echoes throughout the entire vitreous with no posterior vitreous detachment (PVD) or retinal detachment.The left eye was normal to examination.Complete vitreous purulence was interpreted to be incompatible with a sterile uveitis.Upon further questioning, the patient admitted to a slight fever and a sore right elbow, right wrist, and left knee.Septicemia with right eye endogenous endophthalmitis was suspected.
The patient was immediately moved to an adjacent emergency room while infectious disease consultation was obtained, leading to a tentative clinical diagnosis of streptococcus equi septicemia.Intravenous vancomycin was begun immediately after blood culturing, and vitrectomy was promptly performed (KW) with intravitreal injection of 1.0 mg of vancomycin and 2.25 mg of ceftazidime (Video).Due to limited visualization, no periretinal manipulations were performed, leaving a thin layer of purulent cortical vitreous.
The following day the patient had lavage of purulence from the three symptomatic joints with drains left in place for two days, and systemic antibiotic therapy was continued with ceftriaxone.Streptococcus equi subspecies zooepidemicus quickly grew from cultures of blood, the right vitreous, all three affected joints, and from urine.Systemic treatment with ceftriaxone continued throughout a nine-day hospitalization, and cefazoline was continued twice daily after discharge.
During hospitalization, due to persistent and recurrent vitreous purulence, a second vitrectomy with 1.0 mg of vancomycin intravitreal injection was performed (MO) on day three.A superonasal site of infection breakthrough from the choroid, and a surrounding rhegmatogenous retinal detachment with partial PVD, were then discovered.On hospital day five, with the endophthalmitis now seemingly controlled, a third vitrectomy was performed (MS) to repair the extramacular retinal detachment, and silicone oil was placed.Six weeks after discharge, vitrectomy with silicone oil removal and cataract extraction with placement of an intraocular lens were performed (RM).
The patient recovered 20/30 corrected visual acuity in the right eye three months post infection, with a stable retina (Fig. 2).Three years post infection the right eye maintained 20/30 visual acuity with a stable retina and macula (Fig. 3), and a scar at the site of choroidal breakthrough superonasal.

Discussion
The first known case of streptococcus equi endogenous endophthalmitis was mentioned in a brief 1995 French report which focused primarily on meningitis and the systemic infection, with no mention of visual outcome. 5In 2009, a second streptococcus equi endogenous endophthalmitis case was described in which a patient was admitted for fever and hypotension of unknown origin. 3Intravitreal antibiotic injections were performed on the second day of hospitalization, the first day of bilateral vision loss.However, vitrectomy was not performed until the eleventh hospital day, and bilateral blindness resulted from endophthalmitis retinopathy with retinal detachment.A third case was reported in 2015 with meningitis as the presenting feature. 6Left eye vision loss was noted on the second day of hospitalization and vitrectomy was "eventually" performed with "markedly impaired visual acuity" in the affected eye reported as the final outcome.
The current case illustrates the life-saving potential of early recognition by an ophthalmologist, with immediate infectious disease consultation.Such recognition led to early diagnosis and treatment, preventing often-fatal meningitis and systemic deterioration that otherwise may have precluded successful treatment of concomitant streptococcus equi endophthalmitis by recurrent vitrectomy.
While the patient's systemic involvement was recognized relatively early, the endophthalmitis was already advanced on the fourth day of symptoms and was suspected to be caused by a virulent bacterium.To limit endophthalmitis retinopathy, our goals were to restore fundus visualization and to sterilize the vitreous cavity as quickly as possible. 7,8his required both removal of infected tissue by vitrectomy and sustained intravitreal antibiotic levels.
The treatment plan in this case was similar to the approach we have employed successfully in the management of exogenous endophthalmitis following cataract surgery.Using fundus obscuration as the Fig. 1. Anterior segment at presentation, with purulence covering the entire posterior lens surface, obliterating all fundus view.R.E.Morris et al.  indication and vitrectomy as the predominate initial treatment, we previously reported an increase in salvage of 20/40 visual acuity to 79 % of cases, versus 56 % reported using the less interventional Endophthalmitis Vitrectomy Study (EVS) protocol from 1995. [7][8][9] We also cited atrophic defects from endophthalmitis retinopathy as the leading source of retinal detachment in exogenous endophthalmitis, as occurred at the site of infection breakthrough from the choroid in this case of endogenous endophthalmitis (Fig. 2).
The orthopedic treatment of this patient's infected knee, elbow and wrist consisted of initial lavage and placement of drains until purulence was resolved, consistent with the general concepts of concomitant abscess drainage and antibiotic therapy.Similarly, we urge ophthalmologists to consider the importance of early and recurrent purulence removal and antibiotic injection to prevent retinopathy, the primary cause of visual loss in endophthalmitis. 7,9

Conclusions
Despite improvements in medical and surgical management of endogenous endophthalmitis, visual outcomes remain poor.In a 2014 review of 342 endogenous bacterial endophthalmitis cases, Jackson et al. found that more than half of eyes retained less than 20/200 vision, and a quarter of eyes were enucleated/eviscerated. 10 Importantly, only 20 % of eyes were treated with vitrectomy.This case report suggests that more frequent and timely vitrectomy may improve endogenous bacterial endophthalmitis outcomes. 7,8

Patient Consent
The involved patient gave written, informed consent to publication of this case report.

Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Fig. 2 .
Fig. 2. Wide angle image of the retina three months postoperatively, showing the site of original choroidal infection superonasal.Reflection overlying the inferior macula is artifactual.

Fig. 3 .
Fig. 3. Optical coherence tomography (OCT) image of right macula three years post treatment, with visual acuity of 20/30 and moderate retinal atrophy temporally (endophthalmitis retinopathy).Unaffected left macula included for comparison.