Endogenous bacterial endophthalmitis (EE) is an intraocular infection with a poor prognosis. Timely diagnosis and prompt treatment are crucial to prevent vision loss. In this communication, we describe a case of EE caused by Streptococcus pyogenes (Group A Streptococcus [GAS]) in an HIV-positive patient with poorly controlled type 2 diabetes mellitus (DM). A 60-year-old man with a history of HIV and poorly controlled type 2 diabetes, presented with progressive blurry vision, left eye pain, redness, and headache. EE was diagnosed based on the clinical presentation and gram stain analysis of blood culture. Treatment with vitreous tap, intravitreal, topical antibiotics, and systemic antibiotics significantly improved the patient\'s symptoms. The case highlights the rarity of GAS as a causative agent of EE, particularly in patients with risk factors such as HIV infection and DM.

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Background: Gram-negative bacteria are causative agents of endogenous endophthalmitis (EBE). We aim to systematically review the current literature to assess the aetiologies, risk factors, and early ocular lesions in cases of Gram-negative EBE. Methods: All peer-reviewed articles between January 2002 and August 2022 regarding Gram-negative EBE were included. We conducted a literature search on PubMed and Cochrane Controlled Trials. Results: A total of 115 studies and 591 patients were included, prevalently Asian (98; 81.7%) and male (302; 62.9%). The most common comorbidity was diabetes (231; 55%). The main aetiologies were Klebsiella pneumoniae (510; 66.1%), Pseudomonas aeruginosa (111; 14.4%), and Escherichia coli (60; 7.8%). Liver abscesses (266; 54.5%) were the predominant source of infection. The most frequent ocular lesions were vitreal opacity (134; 49.6%) and hypopyon (95; 35.2%). Ceftriaxone (76; 30.9%), fluoroquinolones (14; 14.4%), and ceftazidime (213; 78.0%) were the most widely used as systemic, topical, and intravitreal anti-Gram-negative agents, respectively. The most reported surgical approaches were vitrectomy (130; 24.1%) and evisceration/exenteration (60; 11.1%). Frequently, visual acuity at discharge was no light perception (301; 55.2%). Conclusions: Gram-negative EBEs are associated with poor outcomes. Our systematic review is mainly based on case reports and case series with significant heterogeneity. The main strength is the large sample spanning over 20 years. Our findings underscore the importance of considering ocular involvement in Gram-negative infections.

A 79-year-old woman presented to our hospital with a 10-day history of gradually worsening binocular vision and severe backache. Further investigations revealed poor bilateral best-corrected visual acuities (BCVA), bilateral vitreous opacities, gray-white lesions scattered throughout the retina, and a left iliopsoas abscess on CT that later grew out methicillin-sensitive S. aureus. The abscess was drained and intravenous antibiotics were initiated, but the left eye additionally required intravitreal vancomycin. BCVA for both eyes normalized within 1 year. Intramuscular abscess should be considered as a possible primary lesion in cases of endogenous bacterial endophthalmitis.

BACKGROUND: Group B streptococcus (GBS), a gram-positive coccus that occasionally causes neonatal sepsis or invasive infection in the elderly, has been considered a rare cause of endogenous bacterial endophthalmitis (EBE). However, the number of invasive GBS infections is increasing, particularly in elderly patients with underlying conditions such as diabetes mellitus (DM), cardiovascular disease and cancer. We report 6 cases of EBE caused by GBS and review the literature.
METHODS: Retrospective case series and literature review.
RESULTS: In the current case series, 6 eyes of 6 patients developed EBE caused by GBS. The average age was 73.5 years. The focus of infection included the urinary tract, cellulitis, arthritis, peritonitis, catheter-associated infection and endocarditis. Four patients had DM. While all 6 strains were sensitive to β-lactams (penicillins and cephems), 4 strains were resistant to levofloxacin (no data for 1 isolate). Each case was treated with the systemic antibiotic to which the individual strain was sensitive. All cases showed poor visual acuity at presentation (decimal visual acuity: less than 0.03). Vitrectomy with intravitreal antibiotics injection was performed in 4 cases. Visual acuity recovered in 4 cases and did not recover in 2 cases, even after vitrectomy. The literature review of 53 eyes of 41 patients revealed that 60% of eyes finally lost all vision, and death occurred in 2 cases. Initial visual acuity of less than counting fingers was associated with a final outcome of lost vision. Of 41 patients, 13 (32%) had DM as an underlying medical condition. The most common extra-ocular infection focus was endocarditis (37%).
CONCLUSIONS: DM is common in patients with EBE caused by GBS. While the 4 cases in the current report had a relatively good visual acuity outcome, despite poor initial visual acuity, the literature review indicated that EBE caused by GBS is generally a severe condition with a poor prognosis. The current study also indicates the importance of considering the possibility of endocarditis on encountering EBE caused by GBS.

OBJECTIVE: To better characterize the demographics and outcomes of endogenous bacterial endophthalmitis (EBE).
METHODS: Retrospective observational case series of 49 eyes of 41 patients with EBE evaluated at a single academic center.
RESULTS: Gram stain (p = .395), symptom duration prior to treatment (p = .483), and number of intravitreal antimicrobial injections (p = .421) did not correlate with mean change in VA. There was no significant difference between mean LogMAR VA at initial evaluation (1.7 ± 0.9) and last available follow up (1.4 ± 1.1, p = .15). Patients with bilateral EBE had 7.25 times greater odds of having cancer (95% CI 1.28, 41.14; p = .025).
CONCLUSIONS: EBE in a North American population showed poor visual recovery despite treatment. It was most commonly due to gram-positive bacteria with the most common infectious source being endocarditis. Malignancy should be considered in patients with bilateral EBE.

Human retinal pigment epithelial (hRPE) cells form a selectively permeable monolayer between the neural retina and the highly permeable choroidal vessels. Thus, hRPE cells bear important regulatory functions and are potential targets of pathogens in vivo. Endogenous bacterial endophthalmitis (EBE) is frequently caused by infections with the Gram-positive bacterium Staphylococcus aureus (S. aureus). Upon microbial infection, interferon gamma (IFN-γ), a major cytokine of the adaptive immune response, induces a broad spectrum of effector molecules, such as the tryptophan-degrading enzyme indoleamine 2,3-dioxygenase-1 (IDO1). We stimulated human RPE (hRPE) cells in vitro with proinflammatory cytokines and analyzed the expression levels and enzymatic activities of IDO1 and inducible nitric oxide synthase (iNOS), another antimicrobial effector molecule. The antimicrobial capacity was analyzed in infection experiments using S. aureus and Toxoplasma gondii (T. gondii). Our aim was to characterize the particular importance of IDO1 and iNOS during EBE. We found that an IFN-γ stimulation of hPRE cells induced the expression of IDO1, which inhibited the growth of T. gondii and S. aureus. A co-stimulation with IFN-γ, interleukin-1 beta, and tumor necrosis factor alpha induced a strong expression of iNOS. The iNOS-derived nitric oxide production was dependent on cell-culture conditions; however, it could not cause antimicrobial effects. iNOS did not act synergistically with IDO1. Instead, iNOS activity inhibited IDO1-mediated tryptophan degradation and bacteriostasis. This effect was reversible by the addition of the iNOS inhibitor NG-monomethyl-L-arginine. In conclusion, iNOS mediates anti-inflammatory effects in hRPE cells stimulated with high amounts of IFN-γ together with tumor necrosis factor alpha and Interleukin-1 beta and prevents potential IDO1-dependent tissue damage.

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Endogenous bacterial endophthalmitis, also called metastatic endophthalmitis, is a rare bacterial endophthalmitis derived from distant infectious foci via the bloodstream. This infection can potentially cause not only severe visual disturbance, but also loss of the eyeball or death, as most patients are immunocompromised. This retrospective Japanese multicenter study analyzed 32 eyes in 25 definitive cases. Twelve patients (48.0%) had diabetes mellitus. Typical ocular findings were vitreous haze (87.5%), cells in the anterior chambers (62.5%) and retinal infiltrates (50.0%). Elevated body temperature (64.0%), high serum C-reactive protein (96.0%) and leukocytosis (52.0%) were also frequently observed. Culture positivity rates for intraocular fluid were higher in the vitreous (62.5%) versus aqueous humor (28.6%). High positivity rates were also observed for blood (57.1%) and central venous catheters (100%). The most common pathogen was Staphylococcus aureus (10 cases), including methicillin-resistant S. aureus (4 cases). The next most common pathogen was Klebsiella pneumoniae (7 cases), which was highly associated with liver abscess. Compared to a previous 1991 national multicenter study, there has been a fourfold increase in the ratio of S. aureus. Antibiotic susceptibility tests revealed that all Gram-positives were susceptible to vancomycin and all Gram-negatives were susceptible to third-generation cephalosporins, imipenem/cilastatin, gentamycin and levofloxacin. Prognostic factors influencing poor visual outcome included poor initial visual acuity (p < 0.01), K. pneumoniae (p = 0.027) and gram-negative bacteria (p = 0.014) as the causative bacteria. Intravitreal antibiotic injection in combination with vancomycin and ceftazidime may be applicable for use as part of the standard treatment regimen for EBE.

OBJECTIVE: To report a case of rhegmatogenous retinal detachment in the late stage, despite the fact that it had previously been halted after intravitreal injection of an antimicrobial agent against endogenous bacterial endophthalmitis (EBE).
METHODS: This study involved a 62-year-old male who had previously been diagnosed with septicemia due to liver abscess and the detection of Klebsiella pneumoniae in a culture of his liver abscess, and who underwent ophthalmic examination after his conjunctival hyperemia had failed to improve. Visual acuity could not be measured due to his general condition being poor and his declining level of consciousness. Slit lamp examination revealed bilateral iritis and cataracts, and the fundus was invisible due to vitreous opacity. Ultrasonic B-mode examination showed subretinal abscess and exudative retinal detachment, leading to the diagnosis of EBE. Vitreous injections of antibiotics were administered to both of his eyes. His right eye became affected by phthisis bulbi, but the condition in his left eye subsided, leaving a scarred lesion near the macula. However, complete retinal detachment occurred in his left eye approximately 10 months after the vitreous injection. During vitreous surgery, proliferative membrane formation was observed in the posterior pole area, and an irregular retinal break was detected in the scar margin caused by the traction of the proliferative membrane. After vitreous surgery, the retina was reattached under silicone oil.
CONCLUSIONS: In cases of EBE, even if the inflammation has previously subsided, strict follow-up examinations are necessary, since complications such as rhegmatogenous retinal detachment may occur at a late stage.