Endophthalmitis in the Tertiary Referral Center in Iran; Etiology and Causative Organisms

Copyright © 2017 The Author(s). This is an open-access article distributed under the terms of the Creative Commons Attribution License (http:// creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 1. Background Endophthalmitis is an uncommon, but catastrophic complication of intraocular surgeries and open-globe injuries. Various types of intraocular surgeries may cause endophthalmitis, but improvements in aseptic and microsurgical techniques and the use of antibiotics has reduced the incidence of endophthalmitis.1,2 The incidence of acute-onset endophthalmitis after cataract surgery has been estimated to be 0.07% to 0.26%,3 and it occurs in approximately 4% to 8% of eyes with open-globe injury.4-6 Some studies have reported a much wider variation in incidence rates of endophthalmitis following traumatic injury (4% to 17%).7-11 In Iran, the frequency of endophthalmitis was reported as 0.023% after cataract surgery12 and 2.1% after open-globe injury.13 Likewise, a wide variation in incidence of bleb-associated endophthalmitis, from 0.17% to 13.2%, has been reported.14-29 Considering these wide fluctuations in incidence rates of various types of endophthalmitis and the obvious difference among them, this study aimed to determine the prevalence of various types of endophthalmitis and the causative organism in Iran’s Tertiary Referral Center.

vitreous cells, or marked vitreous consolidation on B-scan ultrasonography.
Each patient's age and gender, type of endophthalmitis, aqueous or vitreous culture results, and treatment method were recorded.
Post-cataract surgery endophthalmitis cases were treated based on the Endophthalmitis Vitrectomy Study results. 30atients with an initial visual acuity of light perception underwent a pars plana vitrectomy, vitreous sampling, and intravitreal injection of 1 mg per 0.1 mL vancomycin and 2.25 mg per 0.1 mg ceftazidim.Aqueous and vitreous aspiration and intravitreal antibiotic injection (1 mg per 0.1 ml vancomycin and 2.25 mg per 0.1 mg ceftazidim) were performed for patients with a visual acuity of hand motion or higher.
Aqueous or vitreous samples obtained by either needle tapping or pars plana vitrectomy were processed for direct smear using Gram and Giemsa stains.Specimens were inoculated onto blood agar, chocolate agar, and thioglycolate broth and incubated at 37°C.Furthermore, cultures on Sabouraud agar at room temperature were used for fungal isolates.Descriptive statistics were used to present quantitative descriptions in this study.

Results
A total of 108 patients had clinical presentation of endophthalmitis and were admitted to Farabi Eye hospital during the study period.The mean patient age was 54.7±19 years.Endophthalmitis involved the left eye in 61.1% of cases, and the right eye was involved in 38.9% of cases.
Positive culture results were found in 43.5% of patients.Hypopyon was absent in 23.1% of patients.The culture positivity rate in patients with hypopyon was 49.4%, but only 24% of patients without hypopyon had positive culture results.

Postoperative Endophthalmitis
The mean age of patients with postoperative endophthalmitis was 63.4 ± 14 years, and 58.1% of cases were men.All patients had unilateral endophthalmitis, and the left eye was affected in 66.2% of cases.
Postoperative endophthalmitis in 68 patients (91.9%) was acute (less than 6 weeks from surgery to presentation) and was chronic in 6 patients (8.1%).All chronic cases had occurred after cataract surgery.The mean time between surgery and presentation to the Tertiary Referral Center was 8.1 ± 7 days for acute cases.
Culture results were positive in 32 cases (43.2%), and the most commonly isolated organism was Gram positive bacteria in 23 cases (71.9% of culture positive cases).Among the bacteria, Streptococcus viridans was the most common isolate (Table 2).

Posttraumatic Endophthalmitis
The mean age of 27 patients with post-traumatic endophthalmitis was 31.4 ± 14 years.Twenty-five patients (88.9%) were men.The right eye was affected in 51.9% of cases.The mean time between trauma and presentation was 3.6 ± 3 days.
Culture results were positive in 10 eyes (37%), and Staphylococcus epidermidis was the most common isolate (Table 3).Intraocular foreign bodies were present in 15 eyes (55.6%).

Other Types of Endophthalmitis
Culture results were positive in 3 of 5 cases with blebassociated endophthalmitis.S. viridians was isolated in two cases, and Candida albicans was isolated in one other patient.
Both patients with endogenous endophthalmitis had undetermined collagen vascular disease and were treated using systematic corticosteroids.Culture results were positive in both of them.Haemophilus sp. was isolated in one case and C. albicans was isolated in the other.

Discussion
The most common type of endophthalmitis in the current study was post-operative endophthalmitis with cataract surgery most frequently contributing to this condition.Somani et al 31 (Canada), Pei-Chang et al 32 (Taiwan), and Falavarjani et al 33 (Iran) reported that cataract surgery was the most common predisposing surgical procedure in postoperative endophthalmitis patients.Since cataract surgery is the most common intraocular surgery, most cases of post-operative endophthalmitis occur after cataract extraction. 34n the current study it was noted that 66.2% of post- Abbreviation: SD, standard deviation.
operative endophthalmitis cases occurred in the left eye.This result is not in agreement with Hani et al 3 and Miller et al 35 who reported that most cases occur in the right eye.They believed that the characteristics of corneal incisions performed by right-handed surgeons may contribute to the higher prevalence of endophthalmitis in the right eye.However, the hand dominance of surgeons was not described in this report; thus, the higher prevalence of endophthalmitis in the right eye may not be correct.The culture positivity rate in patients with postoperative endophthalmitis was 43.2% in this study, which is lower than previously reported, such as the Endophthalmitis Vitrectomy Study that had 67% culture-positive cases 9 and other series seen in the Netherlands (66.4%), 36 India (52.6%), 37 and Taiwan (55%). 32Furthermore, a retrospective study in China recorded a culture-positive rate of 44.2%. 38dditionally, the current study detected positive cultures in 37% of patients with posttraumatic endophthalmitis, which is lower than other reports such as in Saudi Arabia (63.2%). 39This discrepancy may be due in some part to the method of sample collection which was performed by needle aspiration in most cases in the current study.In patients with endophthalmitis, the vitreous body contains inflammatory condensations; so, specimens obtained through needle aspiration may not be sufficient for analysis.Also, the lower culture positivity rate in the current study may be attributable to inappropriate sample collection or handling or the higher frequency of sterile endophthalmitis in the series of this study.
In a retrospective study, Melo et al reported that only 42% of all presumed endophthalmitis cases have had culture-positive results, and most of culture-positive cases were secondary to surgical procedures (62%). 40n the current study, S. viridans was found to be the most frequent cause of postoperative endophthalmitis (37.5%) followed by S. epidermidis (21.9%) and Pseudomonas aeruginosa (12.5%) as the second and third most common organisms, respectively.
In their report, Hani et al. (Saudi Arabia) isolated S. viridans in one case (from 18 cases) of postoperative endophthalmitis, and S. epidermidis was the most frequent causative organism.Pei-Chang et al 32 also reported that S. epidermidis was the most frequent organism causing postoperative endophthalmitis.Furthermore, Zhu et al reported that S. epidermidis was the most common isolated organism in culture-positive post-operative endophthalmitis cases. 38herefore, some geographic variations may contribute to the prevalence of S. viridians infection in Iran.
The most common organism identified in patients with post-traumatic endophthalmitis in the current study was S. epidermidis (70%).This result is compatible with those of Abdulrahman et al 39 and Abu el-Asrar et al. 41 Hani et al 3 reported a lack of hypopyon in 30% of cases.Hypopyon was lacking in 23.1% of cases in the current study.The culture positivity rate was higher in patients who had hypopyon in the initial examination.Thus, the presence of hypopyon at presentation is a strong predictor of positive culture results.
Intraocular foreign bodies (IOFB) were present in 55.6% of posttraumatic endophthalmitis cases in the current study.IOFB were reported in 43% of cases in one study 39 and in 50% of cases in another. 41Education for high risk occupational groups and use of protective eye wears are important factors in the prevention of open-globe injuries and trauma-associated endophthalmitis.

Conclusion
There appears to be a wide variation in endophthalmitis incidence rates; therefore, this study was conducted.Postcataract surgery endophthalmitis is the most frequently seen type of endophthalmitis in the Tertiary Referral Center of Iran.In contrast to many previous reports from other countries, S. viridans is the most common organism contributing to culture-proven endophthalmitis in post-operative patients at this center.Furthermore, S. epidermidis is the most common microbiologic cause of post-traumatic endophthalmitis in this study.

Table 1 .
Demographic Data of 108 Study Subjects

Table 2 .
Microbiological Spectrum in Patients With Postoperative Endophthalmitis

Table 3 .
Microbiological Spectrum in Patients With Posttraumatic Endophthalmitis