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Middle East African Journal of Ophthalmology Middle East African Journal of Ophthalmology
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Year : 2012  |  Volume : 19  |  Issue : 4  |  Page : 361-363  

Isolates and antibiotic resistance of culture-proven endophthalmitis cases presented to a referral center in Tehran

1 Eye Research Center, Rassoul Akram Hospital, Tehran University of Medical Sciences, Tehran, Iran
2 Student Scientific Research Center, Tehran University of Medical Sciences, Tehran, Iran
3 Department of Ophthalmology, Rassoul Akram Hospital, Tehran University of Medical Sciences, Tehran, Iran

Date of Web Publication20-Oct-2012

Correspondence Address:
Khalil Ghasemi Falavarjani
Assistant Professor of Ophthalmology, Eye Research Center, Rassoul Akram Hospital, Sattarkhan-Niayesh Street, Tehran 14455-364
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0974-9233.102740

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Purpose: To evaluate the spectrum of organisms causing endophthalmitis and their resistance pattern to standard antimicrobial agents.
Materials and Methods: Medical records of culture positive eyes treated at Rassoul Akram Hospital for endophthalmitis during the past 5 years were reviewed. Specimens were obtained during pars plana vitrectomy or vitreous tap.
Results: Sixty-five isolates including 36 (55.4%) gram-positive organisms, 28 gram-negative organisms (43.1%), and 1 (1.5%) fungus were studied. The most common organism identified was Coagulase-negative staphylococcus in 16 eyes (24.6%). Among the antibiotics available for intravitreal injection, the least antibiotic resistance was for vancomycin in gram-positive organisms and amikacin and ceftazidime in gram-negative isolates.
Conclusions: Gram-positive isolates were the most prevalent organisms; however, a high isolation rate for gram-negative organisms was obtained. Considering that no single antibiotic provides coverage for all of the organisms, a combination therapy using vancomycin/amikacin or vancomycin/ceftazidime seems to be useful as the initial empiric treatment of suspected bacterial endophthalmitis.

Keywords: Antibiotic, Culture, Endophthalmitis, Microorganism

How to cite this article:
Falavarjani KG, Nekoozadeh S, Modarres M, Parvaresh MM, Hashemi M, Soodi R, Alemzadeh SA. Isolates and antibiotic resistance of culture-proven endophthalmitis cases presented to a referral center in Tehran. Middle East Afr J Ophthalmol 2012;19:361-3

How to cite this URL:
Falavarjani KG, Nekoozadeh S, Modarres M, Parvaresh MM, Hashemi M, Soodi R, Alemzadeh SA. Isolates and antibiotic resistance of culture-proven endophthalmitis cases presented to a referral center in Tehran. Middle East Afr J Ophthalmol [serial online] 2012 [cited 2021 Nov 28];19:361-3. Available from: http://www.meajo.org/text.asp?2012/19/4/361/102740

   Introduction Top

Infectious endophthalmitis is a devastating and sight-threatening condition. It may occur after ocular surgery, ocular trauma, or by hematogenous spread of the organisms to the eye. In previous studies of infectious endophthalmitis, the microbiologic spectrum has been reported to vary depending on the clinical setting and geographic location. [1],[2],[3],[4],[5] In addition, there are some reports of antibiotic resistance among the endophthalmitis isolates. [6] Identifying the causative microorganisms has a great importance for prevention, successful management, and an appropriate treatment of endophthalmitis. In a literature search using PubMed, Scopus, and an Iranian medical database (scientific information database), only one study discussed the spectrum of endophthalmitis isolated organisms in Iran (last assessed December 2011). [7] In this study, 35 of 223 eyes were culture positive; however, the pattern of in vitro antibiotic response was not reported.

The purpose of this study was to evaluate the spectrum of organisms causing culture-proven endophthalmitis and their resistance pattern to commonly used antimicrobial agents.

   Materials and Methods Top

Medical records of all patients admitted for the treatment of the endophthalmitis in the Rassoul Akram Hospital, Tehran, from April 2006 to May 2011 were reviewed. The institutional review board of the Rassoul Akram Eye Research Center approved the study. Only patients with a culture-positive specimen were included. All isolates were obtained from vitreous tap (at the time of antibiotic injection) or parsplana vitrectomy. Vitreous samples were obtained under sterile conditions and inoculated onto the blood agar, Sabouraud's agar, chocolate agar, and thioglycollate broth and properly incubated. Antibiotic susceptibility testing was performed by the disk diffusion method.

   Results Top

Sixty-five isolates from 33 females and 32 males with a mean age of 62.9 ± 18.7 years (range, 2 years to 89 years) were studied. [Table 1] shows the clinical settings in which culture-proven endophthalmitis occurred. The most common settings were acute post cataract surgery in 42 of 65 (64.6%) and endogenous in 9 eyes (13.8%). Endogenous endophthalmitis was associated with diabetes mellitus in three cases and immunosuppression in two patients. No specific association was found in other endogenous endophthalmitis cases. There was a history of corneal laceration secondary to sharp trauma in all eyes with post-traumatic endophthalmitis. Intraocular foreign body was found in three eyes, and the interval between injury and the onset of endophthalmitis ranged between 1 and 28 days.
Table 1: Clinical setting before endophthalmitis and the most prevalent isolated organism

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Overall, 36 of 65 (55.4%) isolates were gram-positive organisms, 28 (43.1%) were gram-negative organisms, and 1 (1.5%) was fungus [Table 2]. The most common gram-positive organism was Coagulase-negative staphylococcus in 38.8%. Among the Staphylococcus aureus isolates, one methicillin-resistant isolate was found. Pseudomonas species were the most commonly identified gram-negative organism (50%). There was no significant correlation between the organisms causing endophthalmitis and the clinical settings in which the culture-proven endophthalmitis occurred (P = 0.9, chi-square test).
Table 2: Endophthalmitis causative organisms

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The results of antibiogram test were not available for 15 eyes. These were all Coagulase-negative Staphylococci. Among the remaining gram-positive identified organisms (21), antibiotic resistance was observed for penicillin G in 7 isolates, oxacillin in 5 isolates, clindamycin in 4 isolates, cefalotin in 2 isolates, ceftazidime in 5 isolates, ciprofloxacin in 2 isolates, ceftriaxone in 2 isolates, and imipenem in 1 isolate. No vancomycin resistance isolate was found. Among the gram-negative organisms, antibiotic resistance was observed for ampicillin in 20 isolates, cefazolin in 14 isolates, ceftriaxone in 8 isolates, gentamycin in 5 isolates, amikacin in 2 isolates, ceftazidime in 3 isolates, ciprofloxacin in two isolates, and imipenem in 3 isolates. Ceftazidime-resistant isolates were sensitive to amikacin, and amikacin-resistant cases were sensitive to ceftazidime and ciprofloxacin.

   Discussion Top

This study reviews the causative organisms of endophthalmitis at a single, referral center over a 5-year period. The majority of the isolates were gram-positive organisms (55.4%); however, gram-negative organisms made up a larger portion (43.1%) than were found in the previous reports including the Endophthalmitis Vitrectomy Study (EVS). [1],[3],[5],[8],[9] The EVS is a hallmark study aimed at evaluating the role of pars plana vitrectomy and intravenous antibiotics in the management of postoperative bacterial endophthalmitis. In EVS the majority of isolates were gram-positive organisms (94%) and in other reports the proportion of the gram-negative organisms was less than 42%. The discrepancy between our results and those reported by EVS and the others may be explained by different inclusion criteria and geographic variation. For example, EVS evaluated only acute-onset endophthalmitis associated with cataract surgery or secondary intraocular lens placement, whereas our study included all categories of endophthalmitis. However, when we considered only acute, postoperative cases, still 45.2% of cases were caused by gram-negative organisms. One plausible explanation is that cases with low-grade endophthalmitis may be treated in the office and cured, so the more severe cases that usually are associated with more virulent organisms such as Pseudomonas were referred to us.

Our results concur with previous studies that show a 100% sensitivity of gram-positive isolates against vancomycin. [1],[3],[5],[9],[10],[11],[12] Among the antibiotics with known intravitreal dosage, amikacin and ceftazidime were the most effective antibiotics against gram-negative organisms. In contrast to previous studies that showed a high resistance rate of gram-negative organisms, [3],[9] we found low resistance rates of 10.7% and 7.1% against gram-negative isolates for ceftazidime and amikacin, respectively. This finding was similar to the EVS results; however, we did not observe any organism resistant to both. The antibacterial spectrum of the carbapenems (including imipenem) has been reported to be broader than that of any other existing antibiotic and includes both gram-positive and -negative organisms. However, carbapenem-resistant strains have been reported recently. [13] We also found imipenem-resistant organisms in both gram-negative and -positive isolates.

Although the effect of topical antibiotics in preventing endophthalmitis is unknown, topical fluoroquinolones are commonly used for perioperative infection prophylaxis in patients undergoing intraocular surgery. [14] Depending on the geographic location, ciprofloxacin sensitivity of the organisms were reported to be between 36% and 88%. [3],[9] We found high sensitivity for both gram-positive and -negative isolates (94.5% and 92.9%, respectively).

Our study has some limitations. The sample size is small. The bacteriology laboratory of our general hospital was not reporting the antibiogram results for Coagulase-negative Staphylococci and considering them like the blood samples as contamination. [15] Our setting is a referral center and some postoperative cases may be treated in offices, hence, our results may not represent the true bacteriologic results of Iranian population. Despite these limitations, to our knowledge, this is the first and largest study reporting endophthalmitis isolates and antibiotic resistance patterns in Iran.

Empirical antibiotic treatment of endophthalmitis should provide broad-spectrum coverage for both gram-positive and gram-negative organisms. Our study supports previous reports recommending the combination treatment including vancomycin/amikacin or vancomycin/ceftazidime for the empirical treatment of endophthalmitis. [1],[16] Future larger studies are needed to confirm our results.

   References Top

1.Han DP, Wisniewski SR, Wilson LA, Barza M, Vine AK, Doft BH, et al. Spectrum and susceptibilities of microbiologic isolates in the Endophthalmitis Vitrectomy Study. Am J Ophthalmol 1996;122:1-17.  Back to cited text no. 1
2.Johnson MW, Doft BH, Kelsey SF, Barza M, Wilson LA, Barr CC, et al. The Endophthalmitis Vitrectomy Study. Relationship between clinical presentation and microbiologic spectrum. Ophthalmology 1997;104:261-72.  Back to cited text no. 2
3.Benz MS, Scott IU, Flynn HW Jr, Unonius N, Miller D. Endophthalmitis isolates and antibiotic sensitivities: A 6-year review of culture- proven cases. Am J Ophthalmol 2004;137:38-42.  Back to cited text no. 3
4.Vedantham V, Nirmalan PK, Ramasamy K, Prakash K, Namperumalsamy P. Clinico-microbiological profile and visual outcomes of post-traumatic endophthalmitis at a tertiary eye care center in South India. Indian J Ophthalmol 2006;54:5-10.  Back to cited text no. 4
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5.Eser I, Kapran Z, Altan T, Ozel Karatas M, Aydin D, Okaygun E, et al. Isolates and antibiotic sensitivity of eighty culture-proven endophthalmitis cases from Istanbul. Ophthalmologica 2008;222:157-60.  Back to cited text no. 5
6.Deramo VA, Lai JC, Winokur J, Luchs J, Udell IJ. Visual outcome and bacterial sensitivity after methicillin-resistant Staphylococcus aureus-associated acute endophthalmitis. Am J Ophthalmol 2008;145:413-7.  Back to cited text no. 6
7.Nili-AhmadAbadi M, Ghasemi F, Karkhaneh R, et al. Endophthalmitis in farabi eye hospital: A review of 223 cases. Iranian J Ophthalmology 2006;19:9-13.  Back to cited text no. 7
8.Kunimoto DY, Das T, Sharma S, Jalali S, Majji AB, Gopinathan U, et al. Microbiologic spectrum and susceptibility of isolates: Part I. Postoperative endophthalmitis. Endophthalmitis Research Group. Am J Ophthalmol 1999;128:240-2.  Back to cited text no. 8
9.Anand AR, Therese KL, Madhavan HN. Spectrum of aetiological agents of postoperative endophthalmitis and antibiotic susceptibility of bacterial isolates. Indian J Ophthalmol 2000;48:123-8.  Back to cited text no. 9
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10.Melo GB, Bispo PJ, Yu MC, Pignatari AC, Höfling-Lima AL. Microbial profile and antibiotic susceptibility of culture-positive bacterial endophthalmitis. Eye (Lond) 2011;25:382-7.  Back to cited text no. 10
11.Miller DM, Vedula AS, Flynn HW Jr, Miller D, Scott IU, Smiddy WE, et al. Endophthalmitis caused by staphylococcus epidermidis: In vitro antibiotic susceptibilities and clinical outcomes. Ophthalmic Surg Lasers Imaging 2007;38:446-51.  Back to cited text no. 11
12.Chisari G. Endophthalmitis: Gram positive ethiological agents and susceptibility to glycopeptides. Curr Clin Pharmacol 2008;3:153-5.  Back to cited text no. 12
13.Carmeli Y, Lidji SK, Shabtai E, Navon-Venezia S, Schwaber MJ. The effects of group 1 versus group 2 carbapenems on imipenem-resistant Pseudomonas aeruginosa: An ecological study. Diagn Microbiol Infect Dis 2011;70:367-72.  Back to cited text no. 13
14.Ciulla TA, Starr MB, Masket S. Bacterial endophthalmitis prophylaxis for cataract surgery: An evidence-based update. Ophthalmology 2002;109:13-26.  Back to cited text no. 14
15.Herwaldt LA, Magdalena G, Kao C, Pfaller MA. The positive predictive value of isolating coagulase-negative staphylococci from blood cultures. Clin Infect Dis 1996;22:14-20.  Back to cited text no. 15
16.Aaberg TM Jr, Flynn HW Jr, Murray TG. Intraocular ceftazidime as an alternative to the aminoglycosides in the treatment of endophthalmitis. Arch Ophthalmol 1994;112:18-9.  Back to cited text no. 16


  [Table 1], [Table 2]

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