
Endophthalmitis following cataract surgery occurs at a rate of 0.28 to 1.6 cases per 1,000 surgeries [1], and Staphylococcus epidermidis is the most frequently isolated pathogen [2]. On the other hand, Enterococcus faecalis, although less common, is more virulent due to its resistance to cefuroxime and its ability to form biofilms on intraocular lenses (IOLs) [3]. E. faecalis is also associated with recurrent endophthalmitis that can occur months after apparent resolution of acute post-cataract surgery endophthalmitis [3]. Another biofilm-forming pathogen of concern, Pseudomonas aeruginosa, is a major cause of nosocomial infections and is often isolated from contaminated surgical instruments [1]. This organism forms biofilms by secreting extracellular polymeric substances that create a protective matrix around the bacterial cells, imparting resistance of these cells to host immune responses [4].
Recent studies suggest that early primary vitrectomy can lead to improved long-term outcomes in post-cataract surgery endophthalmitis [5]. However, the need for IOL explantation concurrent with the initial vitrectomy is a topic of debate. Zhang et al. [6] recommend preserving the IOL during the initial vitrectomy in cases of acute endophthalmitis. However, one case in their study experienced a recurrence, with thick exudate observed in the peripheral vitreous, pars plana, and ciliary bodies. In contrast, Guo et al. [7] reported favorable outcomes after IOL explantation in eyes with acute endophthalmitis following uncomplicated cataract surgery. Among the 10 eyes in their study, five were culture-positive for S. epidermidis and one for Enterococcus [7]. Dave et al. [8] found that IOL explantation resulted in faster recovery but did not significantly improve final visual acuity, bringing into question the necessity of IOL explantation.
Therefore, the need for IOL explantation during initial vitrectomy for infections by biofilm-forming pathogens warrants further investigation. Biofilms provide a protective environment for bacterial cells, protecting them from host immune responses. Understanding the virulence factors of these pathogens are critical for optimizing treatment strategies in post-surgical infections.
In this report, we present a case of acute post-cataract surgery endophthalmitis caused by a dual infection of P. aeruginosa and E. faecalis. We propose that early IOL explantation played a crucial role in facilitating faster recovery and achieving excellent final visual acuity in this case.
The authors strictly adhered to the principles outlined in the Declaration of Helsinki throughout the study. Informed consent was obtained from the patient after discussion of the prognosis of endophthalmitis and the benefits and risks of each treatment option. This case report was approved by the Institutional Review Board of Haeundae Paik Hospital (IRB No: 2024-05-009).
A 48-year-old man was referred from a local clinic with acute vision loss and pain in his left eye. He had undergone uncomplicated phacoemulsification and IOL implantation two days prior. His blood pressure was 110/60 mmHg, heart rate 80 beats/min, respiratory rate 20 breaths/min, and body temperature 36.8℃. The best-corrected visual acuity in the affected eye was hand motion, with intraocular pressure measured at 16 mmHg by a Goldmann applanation tonometer. The limbal conjunctiva appeared severely injected, and multiple large, whitish keratic precipitates were noted. The anterior chamber exhibited 4+ cells and flare reactions according to the Standardization of Uveitis Nomenclature Classification [9]. The hypopyon in the anterior chamber measured approximately 1.5 mm in height (Fig. 1A). The fundus was not visible, and thick vitreous infiltration was observed behind the IOL on B-scan ultrasonography (Fig. 1B). The patient had a history of open-angle glaucoma in both eyes since 2009. He had been using topical dorzolamide/timolol eye drops twice daily and latanoprost eye drops once daily in both eyes. He also had high myopia (axial length: 29-30 mm) and advanced cupping of the optic disc head in both eyes. Samples for culture and sensitivity tests were obtained from the anterior chamber and vitreous of the affected eye at the start of surgery. A standard pars plana vitrectomy was performed using a 25-gauge valved cannula and a wide-field viewing system. Thorough irrigation of the anterior chamber, removal of the anterior vitreous behind the IOL, and removal of the exudate from the pars plana and ciliary bodies were performed with 360˚ scleral indentation. The vitreous cavity was thoroughly irrigated with balanced salt solution. Some retinal hemorrhage and infiltration were observed during surgery, and intravitreal injections of vancomycin 1 mg/0.1 mL (Inno.N Vancomycin HCI Inj 500 mg®; Kukje Pharmaceutical Co.), ceftazidime 2 mg/0.1 mL (Tazime Inj 1g®; Hanmi Pharmaceutical Co.), and moxifloxacin 500 μg/0.1 mL (Vigamox®; Novartis Korea Pharmaceutical Co.) were administered at the end of surgery.
By the following morning, the ocular pain had resolved and the inflammation had stabilized. No hypopyon was observed, but the cells and flare reactions in the anterior chamber remained at 4+. The fundus was dimly visible, but the red reflex had returned. Intravenous moxifloxacin 400 mg/250 mL was administered daily, and fortified eye drops (vancomycin 50 mg/mL and ceftazidime 50 mg/mL) were prescribed for administration every two hours. Homatropine eye drops (Hanlim Homapine®; Hanlim Pharmaceutical Co.) were administered twice daily, and ofloxacin eye ointment was prescribed for administration at night. The patient complained of recurring eye pain 20 hours after the initial vitrectomy. The hypopyon had reformed in the anterior chamber and the red reflex was lost (Fig. 1C). A second vitrectomy was performed immediately, and the IOL and lens capsule were explanted. The IOL and capsule underwent microbiological culture and antibiotic sensitivity testing. Exudation had re-formed on the ciliary bodies, vitreous base, and pars plana; and significant retinal hemorrhage and infiltration were observed during surgery. Extensive vitreous irrigation was performed again. Intravitreal injections of vancomycin 0.5 mg/0.05 mL, ceftazidime 1 mg/0.05 mL, and moxifloxacin 250 μg/0.05 mL were administered after tamponade with 5700 centistokes silicone oil. The intraocular inflammation was stabilized after the second vitrectomy.
On the sixth day of hospitalization, P. aeruginosa was identified in the vitreous fluid culture. The bacteria were sensitive to amikacin, ciprofloxacin, and ceftazidime. On the seventh day, E. faecalis was identified in the culture of the IOL and capsule. This organism was resistant to quinolones, streptomycin, and gentamicin but sensitive to vancomycin. Intravitreal injections of vancomycin, ceftazidime, and moxifloxacin were administered four more times, once every three days. After 18 days of hospitalization, the infection resolved and the best-corrected visual acuity improved to 20/60. Two months after the initial vitrectomy, silicone oil removal, internal limiting membrane peeling, and IOL implantation via scleral fixation were performed (Fig. 1D). The final best-corrected visual acuity of the affected eye was 20/20 at seven months postoperatively. No significant sequelae of endophthalmitis were noted in the macula (Fig. 1E, F).
Pichi et al. [10] described one case of acute and one case of chronic postoperative endophthalmitis caused by biofilm-forming S. epidermidis. That group reported the eventual need for IOL explantation after multiple interventions [10]. Similarly, Lodha et al. [11] reported that endophthalmitis caused by biofilm-forming bacteria required more surgical procedures compared to biofilm-negative bacteria. The polysaccharides produced by these microorganisms enable adhesion to the IOL and posterior lens capsule, facilitating biofilm formation [4]. In our patient, the IOL and posterior lens capsule were the primary sites of biofilm formation, with discernible exudation observed on the adjacent pars plana and ciliary bodies.
In this case, explantation of the IOL was not performed initially, and acute exacerbation of endophthalmitis occurred. Biofilm-forming bacteria can infiltrate the vitreous bands, ciliary bodies, and even the zonules [10]; and explantation of the IOL, lens capsule, and zonules may help reduce the bacterial biofilm burden. While the prognosis for endophthalmitis caused by P. aeruginosa or E. faecalis is typically poor, early extensive vitrectomy in this case resulted in a favorable outcome. In addition, the patient’s young age and absence of diabetes likely contributed to the positive prognosis. Zhang et al. [6] recommended using silicone oil only in the presence of retinal breaks or detachments during vitrectomy for endophthalmitis. In our case, silicone oil was used to prevent inflammation in the vitreous from spreading into the retinal parenchyma because considerable retinal hemorrhage and infiltration were observed during the second vitrectomy. We hypothesize that, if a silicone oil tamponade had been performed during the first vitrectomy, biofilm-forming pathogen spread into the vitreous cavity may have been averted. However, endophthalmitis may have recurred after silicone oil removal if IOL explantation had not been performed at the time of the initial vitrectomy.
In our case, thorough irrigation of the anterior chamber was performed during the initial surgery, but the capsular bag behind the IOL was not irrigated. Guo et al. [7] reported thorough irrigation of the capsular bag during vitrectomy in 10 eyes, and Enterococcus was detected in one case. No recurrence was observed during a 16-month follow-up; however, silicone oil remained in the eye throughout this period, likely because the patient’s final vision was no light perception [7]. Thus, it remains inconclusive whether irrigation of the capsular bag behind the IOL can effectively treat and prevent recurrent endophthalmitis caused by E. faecalis.
P. aeruginosa and E. faecalis are frequently co-isolated in various infections and can form dual-species biofilms. In these biofilms, E. faecalis tends to occupy the lower layers, P. aeruginosa resides at the top. This dual-species biofilm is significantly thicker than those formed by either species alone, potentially enhancing virulence by providing mechanical protection against antimicrobial agents and host immune responses [12]. The delayed identification of pathogens from microbial cultures made it challenging to determine the appropriate treatment at that time. However, upon case review, co-infection of P. aeruginosa and E. faecalis, characterized by a thicker biofilm and potential synergistic pathogenicity, often necessitates more aggressive treatments and provided a rationale for IOL explantation in our patient.
This study reports a single case of endophthalmitis caused by biofilm-forming organisms, greatly limiting generalizability. A more desirable and less invasive treatment option may involve posterior capsulotomy to release and reduce biofilm load during primary or secondary vitrectomy. This may theoretically provide a favorable outcome. Additionally, intravitreal administration of 1.25% povidone-iodine during and after surgery may have eradicated residual microorganisms. Intravitreal povidone-iodine has been shown to be both safe and effective in treating endophthalmitis caused by both E. faecalis and S. epidermidis in rabbit models [13,14] and was effective in treating endogenous endophthalmitis in a case report by Tanaka et al. [15] However, the off-label use of intravitreal povidone-iodine was not approved by our Institutional Review Board. Without ethical approval for its use and re-formation of discernible exudation within 24 hours, we opted to explant the IOL to facilitate near-complete removal of the causative organisms and biofilms. The exudate had re-formed despite aggressive scleral indentation and thorough shaving of the vitreous base during the initial vitrectomy.
In conclusion, primary explantation of the IOL and lens capsule may be considered in cases of endophthalmitis caused by biofilm-forming pathogens. Although identifying the causative pathogen through microbial culture can be time-consuming, suspicions of biofilm-forming pathogens as the cause may be raised by the observation of discernible exudation around the pars plana, ciliary bodies, and lens capsule. Furthermore, IOL, lens capsule, and zonule explantation can be recommended for eyes with acute recurrent endophthalmitis due to the potential involvement of biofilm-forming pathogens.
The authors report no financial support or financial conflict of interest regarding this article. Conflicts of interest outside of this submitted work are as follows: EunAh Kim received payments for lectures from Chong Kun Dang Pharmaceuticals. Chan Ho Cho has no conflict of interest to declare.
Data acquisition (E.K.); Patient care (E.K., C.H.C.); Writing (E.K.); Critical review (All authors); Final approval of the article (All authors)
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