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Exogenous Streptococcus pneumoniae Endophthalmitis in Diabetic Rabbits

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ABSTRACT

Diabetics are at increased risk for eye infections including bacterial endophthalmitis. It is unclear whether the severity of endophthalmitis is greater in these patients due to confounding factors such as pre-existing ocular diseases in some but not others. Therefore, we tested the hypothesis that disease severity and/or bacterial loads would be significantly higher in a Type I diabetic rabbit model of Streptococcus pneumoniae endophthalmitis. Rabbits were treated with alloxan to destroy pancreatic islet cells, or mock-treated with vehicle, and maintained for 10 days before intravitreal infection with S. pneumoniae E353. Clinical scoring of the eyes was performed 24 and 48 hours after infection, followed by euthanasia and vitreous harvest to quantitate bacterial loads. There were no significant differences in clinical scores (P ≥ 0.440) or bacterial loads (P = 0.736), however, 4/12 (33%) of the diabetic rabbits became bacteremic. This finding not only indicates a breakdown in the blood-ocular barrier, but also prompts further investigation into the exploitation of the diabetic eye by the streptococci.

No MeSH data available.


Inflammation (indicated by white arrows) of uninfected, contralateral eyes of diabetic rabbits (a,b). (c) Representative photograph of an uninfected contralateral eye of a control rabbit.
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f3: Inflammation (indicated by white arrows) of uninfected, contralateral eyes of diabetic rabbits (a,b). (c) Representative photograph of an uninfected contralateral eye of a control rabbit.

Mentions: Inflammation was observed in some of the uninfected contralateral eyes of the diabetic rabbits, but not the control rabbits, 48 hours after infection (Fig. 3). Clinical scoring was not performed for these eyes, however, vitreous from the uninfected eyes was collected, serially diluted, and plated after euthanasia to determine whether cross-infection occurred from the infected eyes. These quantitations included 3 contralateral eyes from diabetic rabbits that were moribund and were euthanized just prior to the 48-hour clinical examination. Of the 12 diabetic rabbits, 3 (25%) had culture-positive vitreous in the contralateral eye resembling S. pneumoniae on blood agar (alpha-hemolytic colonies) with no other apparent colony types. Two of these 3 rabbits were the moribund ones that were euthanized without a final clinical examination. The bacterial loads for the contralateral eyes of these 3 rabbits were 8.167 × 103, 4.333 × 104, and 3.833 × 103 CFU/mL. All of the contralateral eyes in the control group of rabbits were culture-negative. There was no significant difference between diabetic and non-diabetic rabbits in vitreous bacterial loads of the infected eyes (Fig. 4, p = 0.736; Cohen’s d = 0.151), nor was there a significant difference for the contralateral eyes (p = 0.084), although the effect size for the contralateral eyes was large (Cohen’s d = 0.776).


Exogenous Streptococcus pneumoniae Endophthalmitis in Diabetic Rabbits
Inflammation (indicated by white arrows) of uninfected, contralateral eyes of diabetic rabbits (a,b). (c) Representative photograph of an uninfected contralateral eye of a control rabbit.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5384200&req=5

f3: Inflammation (indicated by white arrows) of uninfected, contralateral eyes of diabetic rabbits (a,b). (c) Representative photograph of an uninfected contralateral eye of a control rabbit.
Mentions: Inflammation was observed in some of the uninfected contralateral eyes of the diabetic rabbits, but not the control rabbits, 48 hours after infection (Fig. 3). Clinical scoring was not performed for these eyes, however, vitreous from the uninfected eyes was collected, serially diluted, and plated after euthanasia to determine whether cross-infection occurred from the infected eyes. These quantitations included 3 contralateral eyes from diabetic rabbits that were moribund and were euthanized just prior to the 48-hour clinical examination. Of the 12 diabetic rabbits, 3 (25%) had culture-positive vitreous in the contralateral eye resembling S. pneumoniae on blood agar (alpha-hemolytic colonies) with no other apparent colony types. Two of these 3 rabbits were the moribund ones that were euthanized without a final clinical examination. The bacterial loads for the contralateral eyes of these 3 rabbits were 8.167 × 103, 4.333 × 104, and 3.833 × 103 CFU/mL. All of the contralateral eyes in the control group of rabbits were culture-negative. There was no significant difference between diabetic and non-diabetic rabbits in vitreous bacterial loads of the infected eyes (Fig. 4, p = 0.736; Cohen’s d = 0.151), nor was there a significant difference for the contralateral eyes (p = 0.084), although the effect size for the contralateral eyes was large (Cohen’s d = 0.776).

View Article: PubMed Central - PubMed

ABSTRACT

Diabetics are at increased risk for eye infections including bacterial endophthalmitis. It is unclear whether the severity of endophthalmitis is greater in these patients due to confounding factors such as pre-existing ocular diseases in some but not others. Therefore, we tested the hypothesis that disease severity and/or bacterial loads would be significantly higher in a Type I diabetic rabbit model of Streptococcus pneumoniae endophthalmitis. Rabbits were treated with alloxan to destroy pancreatic islet cells, or mock-treated with vehicle, and maintained for 10 days before intravitreal infection with S. pneumoniae E353. Clinical scoring of the eyes was performed 24 and 48 hours after infection, followed by euthanasia and vitreous harvest to quantitate bacterial loads. There were no significant differences in clinical scores (P ≥ 0.440) or bacterial loads (P = 0.736), however, 4/12 (33%) of the diabetic rabbits became bacteremic. This finding not only indicates a breakdown in the blood-ocular barrier, but also prompts further investigation into the exploitation of the diabetic eye by the streptococci.

No MeSH data available.