Intraocular dexamethasone produces a harmful effect on treatment of experimental Staphylococcus aureus endophthalmitis.
BACKGROUND
We created a standardized model of severe Staphylococcus aureus endophthalmitis in the aphakic rabbit eye to test various treatment strategies involving corticosteroid administration in addition to vitrectomy and antibiotic treatment.


METHODS
In 71 aphakic New Zealand albino rabbit eyes, experimental endophthalmitis was created by injecting 10(5) colony-forming units of Staphylococcal aureus. The animals were divided into 5 groups. One control group was followed up without treatment, while 4 groups were treated with vitrectomy and intraocular cefazolin injection. Two groups were also treated with intramuscular methylprednisolone, 1 group beginning on the day of surgery and 1 group beginning on the following day. In the final group, dexamethasone, 400 micrograms, was injected into the vitreous cavity at the close of surgery. Culture results were compared on the first 2 days after surgery. Inflammatory scores, including development of total corneal opacity, were assessed over a 21-day follow-up period, and histopathologic grading was carried out at the conclusion of the clinical observations.


RESULTS
Simultaneous administration of systemic corticosteroids beginning on the day of vitrectomy decreased inflammatory scores 1 week after institution of therapy but did not affect final scores. Delay of initiation of intramuscular corticosteroid until the first postoperative day negated the positive effects. Administration of intraocular corticosteroids was associated with an increase in inflammatory scores throughout the period of observation, an increase in percentage of eyes that developed opaque corneas, an increase in choroidal inflammation graded moderate or severe, and an increase in retinal necrosis compared with vitrectomy and cefazolin injection alone.


CONCLUSIONS
This data suggest caution in the use of intraocular corticosteroids in treatment of severe endophthalmitis.
Meredith
T A
TA
St Louis University School of Medicine, Missouri, USA.
Aguilar
H E
HE
Drews
C
C
Sawant
A
A
Gardner
S
S
Wilson
L A
LA
Grossniklaus
H E
HE
D000818:Animals; D002437:Cefazolin / Q000627:therapeutic use; D002511:Cephalosporins / Q000627:therapeutic use; D017024:Chemotherapy, Adjuvant; D002833:Choroiditis / Q000139:chemically induced; D003318:Corneal Opacity / Q000139:chemically induced; D003907:Dexamethasone / Q000009:adverse effects* / Q000627:therapeutic use; D004195:Disease Models, Animal; D009877:Endophthalmitis / Q000188:drug therapy* / Q000382:microbiology; D005128:Eye Diseases / Q000139:chemically induced*; D015818:Eye Infections, Bacterial / Q000188:drug therapy* / Q000209:etiology; D005938:Glucocorticoids / Q000009:adverse effects* / Q000627:therapeutic use; D008775:Methylprednisolone / Q000627:therapeutic use; D009336:Necrosis; D011817:Rabbits; D012160:Retina / Q000187:drug effects / Q000473:pathology; D013203:Staphylococcal Infections / Q000188:drug therapy* / Q000209:etiology; D013211:Staphylococcus aureus; D014821:Vitrectomy
D002511:Cephalosporins; D005938:Glucocorticoids; D003907:Dexamethasone; D002437:Cefazolin; D008775:Methylprednisolone