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Updated: Jun 27, 2026
Intravitreal Injection and Quantitation of Infection Parameters in a Mouse Model of Bacterial Endophthalmitis
Published on: February 6, 2021
Apoptotic mechanisms within the retina in Staphylococcus epidermidis experimental endophthalmitis
Nikolaos M Pharmakakis1, Ioannis K Petropoulos, Constantine D Georgakopoulos
1Department of Ophthalmology, School of Medicine, University of Patras, Patras, Greece. npharmak@med.upatras.gr
Aim:
To investigate the potential involvement of apoptosis and its regulators Bcl-2, Bax, and Fas within the retina in Staphylococcus epidermidis experimental endophthalmitis.
Methods:
Endophthalmitis was induced in 48 male Lewis rats by unilateral 25-mircrol intravitreal injection of 7,000 viable organisms of slime-producing S. epidermidis strain ATCC 35983 (experimental group). Forty-eight other Lewis rats received a similar sterile normal saline injection (control group). The injected eyes were graded for clinical inflammation and were removed in groups at 6, 12, 24, 48, 72, and 168 hours post-injection. After surgical separation, retinal tissue specimens were fixed, and paraffin sections underwent hematoxylin-eosin staining, immunohistochemistry against Bcl-2, Bax, and Fas, and TUNEL assay for detection of apoptotic cells. Following morphometric analysis, the apoptotic body index (ABI) was calculated.
Results:
While Bcl-2 expression was absent, Bax and Fas expression and apoptosis in ganglion cells, bipolar cells, and photoreceptors, were significantly higher in the experimental group compared to the control group (P < 0.05). In the experimental group, inflammation peaked at 24 hours, Bax and Fas expression at 48 hours and the ABI at 72 hours post-injection.
Conclusion:
Apoptosis is increased within the retina in S. epidermidis experimental endophthalmitis through upregulation of Bax and Fas, peaking soon after peak inflammation.
