Successful management of post-traumatic vancomycin-resistant enterococcus endophthalmitis

Non-faecium non-faecalis enterococci: a review of clinical manifestations, virulence factors, and antimicrobial resistance

SUMMARYEnterococci are a diverse group of Gram-positive bacteria that are typically found as commensals in humans, animals, and the environment. Occasionally, they may cause clinically relevant diseases such as endocarditis, septicemia, urinary tract infections, and wound infections. The majority of clinical infections in humans are caused by two species: Enterococcus faecium and Enterococcus faecalis. However, there is an increasing number of clinical infections caused by non-faecium non-faecalis (NFF) enterococci. Although NFF enterococcal species are often overlooked, studies have shown that they may harbor antimicrobial resistance (AMR) genes and virulence factors that are found in E. faecium and E. faecalis. In this review, we present an overview of the NFF enterococci with a particular focus on human clinical manifestations, epidemiology, virulence genes, and AMR genes.

Endophthalmitis caused by Enterococcus casseliflavus: a systematic review of literature

Introduction

Enterococcus casseliflavus is a rare pathogen in human infections, despite being widely distributed in natural environments. This systematic review aims to evaluate the evidence related to endophthalmitis caused by E. casseliflavus.

Methods

A thorough search of PubMed, PubMed Central, and Scopus databases was conducted, covering the period up to October 2022.

Results

A total of 53 records were identified, with 8 studies reporting a total of 21 cases meeting the inclusion criteria. Among these studies, 7 described isolated case reports, while 1 study described 14 cases. The overall quality of the reports was good, as all articles were determined to have low risk of bias. Vancomycin susceptibility was reported in only one case of isolated case reports, while the remaining cases were all vancomycin resistant. With regard to management, in most cases intravenous ampicillin and linezolid were administered, while only one study reported administration of vancomycin.

Conclusions

Ophthalmologists should be aware of the potential for E. casseliflavus to cause endophthalmitis infections and the challenges associated with its intrinsic resistance to vancomycin.

Enterococcus casseliflavus Infection: A Review of Clinical Features and Treatment

Some Enterococcus species, including Enterococcus faecalis and E. faecium, are increasingly becoming a common cause of nosocomial infections, accounting for the majority of human enterococcal infections, while other species, such as E. casseliflavus, have also been shown to be pathogenic to humans due to the increase in immunocompromised patients. These infections vary widely in their mode of transmission, symptoms, and other characteristics. Treatment is difficult in some cases because enterococci are resistant to numerous antimicrobial agents. Enterococcus faecalis and E. faecium are the best-known opportunistic pathogens, but others, including E. casseliflavus, occasionally cause opportunistic infections. This review summarizes the clinical features of E. casseliflavus infections and discusses effective therapeutic strategies. Bacteremia was the most common form of E. casseliflavus infections. Because E. casseliflavus carries the VanC gene, which confers resistance to vancomycin, less resistant drugs such as ampicillin were found more effective in treating the bacteremia. The second most common form of E. casseliflavus infection was trauma-induced endophthalmitis. This was commonly reported in active young to middle-aged patients. Vitreoretinal surgery and local or systemic administration of sensitive antimicrobial agents seem to be key to successful treatment. Other conditions such as infective endocarditis, meningitis, peritonitis, and pyothorax have also been reported as forms of E. casseliflavus infection. This review clarifies the clinical features of E. casseliflavus infection and provides important insights into its treatment.

Intracameral Bacteriophage Injection as Postoperative Prophylaxis for Enterococcus faecalis-Induced Endophthalmitis After Cataract Surgery in Rabbits

Purpose

Post–cataract surgery bacterial endophthalmitis is a serious postoperative complication, and Enterococcus spp.–induced endophthalmitis reportedly has a particularly poor visual prognosis. This study aimed to demonstrate the prophylactic effect of postoperative intracameral phage administration in Enterococcus faecalis–induced endophthalmitis after cataract surgery in rabbits.

Methods

Endophthalmitis was induced in rabbits by injecting E. faecalis into the anterior chamber just after lensectomy while simultaneously administering either phage phiEF24C-P2 or vehicle. Retinal function was evaluated using electroretinography. The number of viable bacteria and myeloperoxidase (MPO) activity in the eye and histopathologic examinations were analyzed 48 hours after infection.

Results

In the vehicle-treated group, retinal function at 24 hours after infection was impaired, and the number of viable bacteria and MPO activity in the eye increased 48 hours later. In the phage-administered group, retinal function was maintained; the number of viable bacteria and MPO activity were significantly suppressed. Histopathologic examinations showed disruption of the retinal layers and the presence of numerous E. faecalis in the lens capsule and vitreous cavity in vehicle-treated eyes. In contrast, retinal structures were intact, and no E. faecalis staining was observed in phage-treated eyes. No retinal dysfunction was observed in the group that received phage only without lensectomy; almost no phage was detected in the eyes after 14 days of treatment.

Conclusions

Phage administration in the anterior chamber did not cause retinal dysfunction and suppressed postoperative endophthalmitis in rabbits.

Translational Relevance

In vivo results of intracameral phage administration suggest that phages are a promising prophylactic candidate for postoperative endophthalmitis.

Enterococcus gallinarum endophthalmitis and meningitis in an allogeneic hematopoietic stem cell transplant patient: A case report and literature review

Endogenous endophthalmitis caused by Enterococcus gallinarum, an organism with intrinsic resistance to vancomycin, has rarely been reported. We present a case of persistent E. gallinarum bacteremia in a female recipient of hematopoietic stem cell transplant (HSCT) complicated by endophthalmitis and meningoventriculitis, resulting in a fatal outcome despite treatment with intravenous ampicillin and daptomycin. Treatment of endophthalmitis often presents a challenge due to the lack of options for antimicrobials with reliable ocular penetration. Therapeutic decisions can become particularly complex with the involvement of drug-resistant pathogens and host characteristics that limit the choice of antimicrobials due to drug toxicity. This case illustrates a rare manifestation of an opportunistic pathogen.

Antimicrobial guide to posterior segment infections

PURPOSE

This review article is meant to serve as a reference guide and to assist the treating physician in making an appropriate selection and duration of an antimicrobial agent.

METHODS

Literature review.

RESULTS

Infections of the posterior segment require prompt medical or surgical therapy to reduce the risk of permanent vision loss. While numerous options exist to treat these infections, doses and alternative therapies, especially with contraindications for first-line therapy, are often elusive. Antimicrobial agents to treat posterior segment infections can be administered via various routes, including topical, intravitreal, intravenous, and oral.

CONCLUSIONS

Although there are many excellent review articles on the management of endophthalmitis, we take the opportunity in this review to comprehensively summarize the appropriate antimicrobial regimen of both common and rare infectious etiologies of the posterior segment, using evidence from clinical trials and large case series.

Intravitreal linezolid in the management of vancomycin-resistant enterococcal endophthalmitis

Purpose

Linezolid is a synthetic antibiotic, the first of the oxazolidinone class, used for the treatment of infections caused by multi-resistant bacteria including Streptococcus, methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE). We report on a case of endophthalmitis caused by vancomycin-resistant Enterococcus feacium treated with intravitreal linezolid. It has proved efficacious in animal models but its safety in humans is not fully known.

Observations

An 84-year-old man who had phacoemulsification surgery and anterior chamber intraocular lens due to posterior capsule rent. Visual acuity (VA) following surgery was 6/24 uncorrected. The following week he developed signs of endophthalmitis, characterized by corneal infiltration and keratic precipitates, with anterior chamber and vitreous haze. Cultures yielded no growth, while repeated treatments with intravitreal vancomycin, ceftazidime, and amphotericin B did not control the infection. Vitrectomy was performed twice during the patient's course, with intravitreal amikacin injection after the second vitrectomy, but poor control of the endophthalmitis persisted. After several weeks of limited response to treatments, the diagnosis was finally made using Giemsa stain of direct smear which showed characteristic morphology of Enterococcus faecium. Linezolid, one of the oxazo-lidinones, was initially given in oral form 600 mg BID for three weeks, but did not prove efficacious. Subsequently, intravitreal linezolid 200 mcg in 0.1ml was injected, which cleared the vitreous and cornea infection within a week. However, there was a residual exudative detachment of the retina in the posterior pole, leaving the patient with a final vision of hand movement.

Conclusion and importance

Vancomycin-resistant enterococcus is a rare cause of endophthalmitis. Intravitreal linezolid is an effective treatment, but the subsequent exudative retinal detachment may have been related to this novel therapy.

The cereus matter of Bacillus endophthalmitis

Bacillus cereus (B. cereus) endophthalmitis is a devastating intraocular infection primarily associated with post-traumatic injuries. The majority of these infections result in substantial vision loss, if not loss of the eye itself, within 12-48 h. Multifactorial mechanisms that lead to the innate intraocular inflammatory response during this disease include the combination of robust bacterial replication, migration of the organism throughout the eye, and toxin production by the organism. Therefore, the window of therapeutic intervention in B. cereus endophthalmitis is quite narrow compared to that of other pathogens which cause this disease. Understanding the interaction of bacterial and host factors is critical in understanding the disease and formulating more rational therapeutics for salvaging vision. In this review, we will discuss clinical and research findings related to B. cereus endophthalmitis in terms of the organism's virulence and inflammogenic potential, and strategies for improving of current therapeutic regimens for this blinding disease.

Exogenous endophthalmitis caused by Enterococcus casseliflavus: A case report

BACKGROUND

Endophthalmitis caused by Enterococci is rare, and cases involving vancomycin-resistant enterococci are even rarer. We report the first case of Enterococcus casseliflavus endophthalmitis associated with injury caused by a pig. We also review reported cases of exogenous endophthalmitis caused by Enterococcus casseliflavus and discuss the clinical management and prognosis of this disease.

CASE SUMMARY

A 43-year-old man with no previous visual problems complained of endophthalmitis in his left eye following injury caused by a pig. Visual acuity was light perception and B-ultrasonography revealed vitreous opacities with retinal detachment. He was treated with intravitreal vancomycin and ceftazidime after refusing vitrectomy. However, the vitreous opacities and retinal detachment deteriorated and he underwent vitrectomy 5 d post-injury. Intraoperatively, advanced rhegmatogenous and tractional retinal detachment with proliferative vitreoretinopathy were observed. On postoperative day 5, vitreous cultures grew Gram-positive cocci identified as Enterococcus casseliflavus. A 2-wk course of intravenous ampicillin and dexamethasone was commenced. On postoperative day 14, visual acuity improved to hand movement. At 6 mo post-injury, visual acuity improved to 20/667, but optic atrophy was present.

CONCLUSION

Systemic administration of linezolid in the treatment of Enterococcus casseliflavus endophthalmitis can improve visual acuity. However, intravitreal amikacin should be considered despite concerns of toxicity when oral linezolid fails to prompt improvement.

Therapeutic Effects of Intravitreously Administered Bacteriophage in a Mouse Model of Endophthalmitis Caused by Vancomycin-Sensitive or -Resistant Enterococcus faecalis

Endophthalmitis due to infection with Enterococcus spp. progresses rapidly and often results in substantial and irreversible vision loss. Given that the frequency of this condition caused by vancomycin-resistant Enterococcus faecalis has been increasing, the development of novel therapeutics is urgently required. We have demonstrated the therapeutic potential of bacteriophage ΦEF24C-P2 in a mouse model of endophthalmitis caused by vancomycin-sensitive (EF24) or vancomycin-resistant (VRE2) strains of E. faecalis Phage ΦEF24C-P2 induced rapid and pronounced bacterial lysis in turbidity reduction assays with EF24, VRE2, and clinical isolates derived from patients with E. faecalis-related postoperative endophthalmitis. Endophthalmitis was induced in mice by injection of EF24 or VRE2 (1 × 10⁴ cells) into the vitreous. The number of viable bacteria in the eye increased to >1 × 10⁷ CFU, and neutrophil infiltration into the eye was detected as an increase in myeloperoxidase activity at 24 h after infection. A clinical score based on loss of visibility of the fundus as well as the number of viable bacteria and the level of myeloperoxidase activity in the eye were all significantly decreased by intravitreous injection of ΦEF24C-P2 6 h after injection of EF24 or VRE2. Whereas histopathologic analysis revealed massive infiltration of inflammatory cells and retinal detachment in vehicle-treated eyes, the number of these cells was greatly reduced and retinal structural integrity was preserved in phage-treated eyes. Our results thus suggest that intravitreous phage therapy is a potential treatment for endophthalmitis caused by vancomycin-sensitive or -resistant strains of E. faecalis.