Biomedical subjects

S A Adamu

Publications and source records attributed to S A Adamu.

11 recordsLinked to original sources

PubMed1998

Timing of dexamethasone treatment in experimental Staphylococcus aureus endophthalmitis.

PURPOSE: This study sought to determine whether intravitreal dexamethasone with vancomycin preserves retinal function in eyes with experimental Staphylococcus aureus endophthalmitis better than intravitreal vancomycin alone. METHODS: Twenty-four rabbits received intravitreal injections in both eyes with S. aureus. Right eyes were treated with intravitreal dexamethasone plus vancomycin and left eyes were treated with vancomycin alone at 24, 36, 48, or 72 hours after inoculation. Evaluation was performed by slit-lamp biomicroscopy, indirect ophthalmoscopy, and electroretinogram. Vitreous humor cultures and histopathologic examinations were performed on the eyes after the rabbits were killed. RESULTS: The combination of intravitreal dexamethasone and vancomycin resulted in significantly less inflammation than vancomycin alone at 24 and 36 hours after inoculation, but electroretinograms showed significantly better preservation only at 36 hours after bacterial inoculation. Viable bacteria were cultured from eyes treated 48 and 72 hours after inoculation. CONCLUSION: Intravitreal dexamethasone was found to be beneficial by electroretinography when administered 36 hours after infection. In the authors' model, a single intravitreal injection of vancomycin with or without the addition of dexamethasone was insufficient to sterilize eyes 48 and 72 hours after bacterial inoculation.

Animals↗

PubMed1996

The effect of Staphylococcus aureus phage lysate vaccine on a rabbit model of staphylococcal blepharitis, phlyctenulosis, and catarrhal infiltrates.

PURPOSE: To evaluate the effect of Staphylococcus aureus phage lysate (SPL) vaccination on the development of blepharitis, corneal phlyctenules, and catarrhal infiltrates and on the development of antibodies and the delayed-type hypersensitivity response to S. aureus. METHODS: Eighty rabbits received an intradermal immunization of cell wall-complete Freund's adjuvant followed by a booster immunization. Rabbits were given topical applications of viable S. aureus in both eyes and 40 rabbits received subcutaneous SPL vaccinations. Clinical observations were made weekly. An enzyme-linked immunosorbent assay was used to measure IgG, IgA, and IgM antibody levels to ribitol teichoic acid in sera, corneas, and tears. The delayed-type hypersensitivity response was evaluated by skin testing after subcutaneous injection of staphylococcal antigens. RESULTS: In the SPL-vaccinated group, phlyctenules developed in eight of 40 rabbits while blepharitis developed in 13 of 40. In the nonvaccinated group, phlyctenules developed in three of 40 rabbits and blepharitis developed in five of 40. The number of rabbits with blepharitis was significantly higher in the SPL-vaccinated group than in the nonvaccinated group. In general, the antibody response to ribitol teichoic acid was enhanced, while the delayed-type hypersensitivity response to S. aureus was depressed. CONCLUSIONS: Vaccination with SPL was not found to have a beneficial effect on the development of blepharitis, phlyctenules, and catarrhal infiltrates in our rabbit model.

Animals↗

PubMed1995

Immunopathologic features of Staphylococcus aureus endophthalmitis in the rat.

PURPOSE: To study the clinical, histopathologic, and immunologic responses to Staphylococcus aureus endophthalmitis in rats. METHODS: Experimental Lewis rats received an intravitreal injection of viable S. aureus (65 organisms), and control rats received sterile saline. The clinical scores, cellular infiltrate, delayed hypersensitivity reaction in skin tests, and serum and vitreous enzyme-linked immunosorbent assay titers of immunoglobulin (Ig) M, IgG, and IgA to ribitol teichoic acid (RTA), the major antigenic determinant of S. aureus cell wall, were measured and compared on days 3, 7, 10, 14, 21, and 30. The differences were statistically assessed using Mann-Whitney nonparametric t-tests and analysis of variance. RESULTS: The red reflex was abolished in the majority of rats between days 3 and 21. Ocular inflammation resolved by day 30. The vitreous of eyes injected with S. aureus showed bacterial growth on days 3 and 7, followed by a decrease in numbers on days 10 and 14 and disappearance on days 21 and 30. In the vitreous, a peak neutrophil count was observed at day 3 that rapidly declined by day 7. The number of lymphocytes and plasma cells peaked on day 3 but declined more slowly. Plasma cells and Mott cells were seen on days 10 and 14, suggesting intraocular antibody production. IgM titers to RTA increased progressively in serum and vitreous, reached a peak on day 21, and declined on day 30. A weak IgG but absent IgA response to RTA was observed in serum and vitreous. S. aureus endophthalmitis was not associated with delayed hypersensitivity to the bacteria in skin tests. CONCLUSIONS: S. aureus endophthalmitis is associated with the infiltration of neutrophils, lymphocytes, monocytes, and plasma cells in vitreous. Neutrophils, the predominant infiltrating cells, may be involved in bactericidal activity and opsonophagocytosis. In rat staphylococcal endophthalmitis, IgM rather than IgG may be the protective antibody.

Animals↗

PubMed1994

Complement system and host defense against staphylococcal endophthalmitis.

PURPOSE: The authors studied the role of the complement system in host defense against Staphylococcus epidermidis and S. aureus endophthalmitis. METHODS: Guinea pigs in the S. epidermidis model received an intravitreal injection of 7000 viable organisms, and guinea pigs in the S. aureus model received 50 viable organisms. The experimental animals in each model were decomplemented with intraperitoneal (IP) injections of cobra venom factor, whereas the control animals received IP injections of normal saline. Mean log bacterial counts in the vitreous and mean serum complement titers were compared in the experimental and control animals in each model on days 1, 2, 3, and 7. RESULTS: In the S. epidermidis model, mean log bacterial counts in the vitreous were significantly higher in the experimental group than the control group on days 1 and 2 (P < 0.01) and on day 3 (P < 0.05). Mean serum complement titers were significantly lower in the experimental group at all days (P < 0.01). In the S. aureus model, mean log bacterial counts in the vitreous were significantly higher in the experimental group than the control group on day 2 (P < 0.05) and day 3 (P < 0.01). Mean serum complement titers were significantly lower in the experimental group on days 1, 2, and 3 (P < 0.01), but not on day 7. CONCLUSION: These results suggest that decomplemented guinea pigs show impaired host defense to S. epidermidis and S. aureus endophthalmitis and that this defense is restored as complement levels approach normal.

Animals↗

PubMed1993

Collagen shields impregnated with gentamicin-dexamethasone as a potential drug delivery device.

We investigated the ability of collagen shields impregnated with gentamicin sulfate and dexamethasone to deliver medication into rabbit eyes. We compared the aqueous humor gentamicin and dexamethasone levels delivered by collagen shield and subconjunctival injection therapy at five time points over a ten-hour period, by using a fluorescence polarization immunoassay and high-pressure liquid chromatography. Our in vitro studies showed that impregnated collagen shields released most of the gentamicin within the first 30 minutes of elution, whereas dexamethasone was released gradually over a ten-hour period. The collagen shields impregnated with gentamicin and dexamethasone produced aqueous gentamicin levels that were significantly lower (P = .014) than those produced by subconjunctival injection therapy at 30 minutes and that were comparable to subconjunctival injection therapy at the other time points. Minimum inhibitory concentrations of gentamicin (approximately 4 micrograms) were observed in aqueous humor within 30 minutes in rabbits that received subconjunctival injections and at one hour in rabbits treated with impregnated collagen shields. The impregnated collagen shields produced aqueous dexamethasone levels that were significantly lower (P = .004) than those produced by subconjunctival injection therapy at one hour, significantly higher (P = .028) than subconjunctival injection therapy at six hours, and comparable to subconjunctival injection therapy at the other time points. Collagen shield delivery of gentamicin-dexamethasone may be comparable to subconjunctival injections and provide an alternative therapy after intraocular surgery.

Animals↗

PubMed1992

Immune response to Staphylococcus epidermidis-induced endophthalmitis in a rabbit model.

Although Staphylococcus epidermidis is the most common cause of postoperative pseudophakic endophthalmitis, little is known about the immune response to S. epidermidis-induced endophthalmitis. Using a rabbit model, the immune response to an intravitreal injection of 7000 S. epidermidis (group 1) or 30,000 S. epidermidis (group 2) organisms was investigated. Clinical evaluations showed that rabbits in group 2 had a more severe inflammatory reaction in the conjunctiva, cornea, iris, and vitreous than those in group 1. The inflammatory reaction in group 1 largely resolved by day 30; group 2 continued to show a severe inflammatory response. Histopathologic findings correlated with clinical findings, with rabbits in group 2 showing a more severe inflammatory reaction in both the anterior and posterior segments of the globe. Positive vitreous cultures for S. epidermidis were present in rabbits in group 1 on days 3, 7, 10, 14, and 21 but not thereafter. However, group 2 had higher vitreous colony counts at days 3, 7, and 14 and negative vitreous cultures thereafter. Neither group showed delayed hypersensitivity to S. epidermidis antigens (evaluated by skin tests). Serum immunoglobulin (Ig) G antibody levels to phenol-inactivated S. epidermidis and glycerol teichoic acid (GTA) increased progressively, reached a peak at days 10-14, and then declined in both groups. Serum IgA antibody levels to these antigens were not detected. Group 2 had a more prolonged IgG antibody response in vitreous and aqueous than group 1. Tear fluid showed the weakest IgG and IgA antibody response to S. epidermidis and GTA. S. epidermidis-induced endophthalmitis was associated with a humoral but not a delayed hypersensitivity response to this organism.

Animals↗

PubMed1991

Immune response to Staphylococcus aureus endophthalmitis in a rabbit model.

Staphylococcus aureus is an important cause of severe bacterial endophthalmitis. Both immunoglobulin (Ig) G and A antibody titers to ribitol teichoic acid (RTA), the major antigenic determinant of the S. aureus cell wall, were measured by an enzyme-linked immunosorbent assay in serum, tears, aqueous, and vitreous on days 3, 7, 10, 14, 21, and 30 after intravitreal injection of viable S. aureus in rabbits. Clinical examination showed vitreous opacification in all rabbits from days 7-30. Histopathologic examination showed acute inflammation on day 3 and chronic inflammation on days 7-30 in the conjunctiva, cornea, iris, ciliary body, and trabecular meshwork. The vitreous cavity contained neutrophils and necrotic cells on all days. Retinal necrosis was present on days 14-30. Lymphoid follicles with plasma cells were identified in the conjunctiva, ciliary body, and choroid. The vitreous of experimental eyes showed increasing numbers of bacteria from days 3-14, followed by a decrease in numbers on day 21 and absence of viable bacteria on day 30. Increases in IgG antibody levels to RTA were first detected in serum where they were higher than in tears, aqueous, and vitreous until day 14. Vitreous IgG antibody levels to RTA in experimental eyes exceeded all other samples on day 14 and progressively increased thereafter; the other samples declined. The IgA antibody levels were increased in tears on day 14 and in the vitreous of experimental eyes on days 14, 21, and 30. Vitreous IgG antibody levels to RTA were substantially higher than vitreous IgA antibody levels. An inverse correlation was found between vitreous IgG antibody levels and positive vitreous cultures, suggesting that the humoral immune response may be important in the spontaneous sterilization of the vitreous in this model.

Animals↗

PubMed1991

Antibody studies in a rabbit model of corneal phlyctenulosis and catarrhal infiltrates related to Staphylococcus aureus.

Hypersensitivity to ribitol teichoic acid (RTA), the major antigenic determinant of Staphylococcus aureus, may be important in a rabbit model of corneal phlyctenules and catarrhal infiltrates. Over a 5-month period, an enzyme-linked immunosorbent assay was used to measure immunoglobulin (Ig) G and IgA antibody levels to RTA in sera, tears, and corneas from rabbits immunized using the following routes: Group 1, intradermal injections of S. aureus cell wall (CW) mixed with complete Freund's adjuvant (CFA); Group 2, subconjunctival injections of CW-CFA; Group 3, prolonged topical application of viable S. aureus to the eye; Group 4, intradermal injections of CW-CFA plus prolonged topical application of viable S. aureus; and Group 5, subconjunctival injections of CW-CFA plus prolonged topical application of viable S. aureus. Over the 5-month period, the IgG and IgA antibody levels were correlated to RTA with the development of corneal phlyctenules and catarrhal infiltrates. The IgG titers to RTA were higher than IgA titers in serum, tears, and cornea. The highest antibody titers were IgG titers in cornea. Only rabbits immunized by intradermal or subconjunctival injections of CW-CFA followed by prolonged topical application of viable S. aureus (Groups 4 and 5) developed moderate to severe conjunctival hyperemia and edema with corneal phlyctenules and catarrhal infiltrates. When corneal lesions developed between 2-3 months, both groups had the highest corneal IgG and IgA antibody titers to RTA with IgG titers being more than 60 times higher than IgA titers. In the remaining 2 months of the study, the conjunctival response in both groups decreased from moderate-to-severe to mild, and no new corneal lesions developed, despite continued topical application of viable S. aureus and elevated antibody titers in cornea, serum, and tears. In this study, IgG and IgA antibody levels to RTA were measured in serum, tears, and cornea in a rabbit model of corneal phlyctenules and catarrhal infiltrates, and the antibody response was correlated with the development of these hypersensitivity lesions.

Animals↗

PubMed1987

Ocular immunity to Staphylococcus aureus.

Staphylococcus aureus is an important cause of infectious disease of the eye and hypersensitivity lesions of the cornea including phlyctenules and catarrhal infiltrates. Because little is known about ocular immunity to S. aureus, we measured antibody levels to ribitol teichoic acid, the major antigenic determinant of S. aureus, in rabbit serum and tears using an enzyme-linked immunosorbent assay after immunization with S. aureus antigens using the following routes: intradermal injection of cell wall mixed with complete Freund's adjuvant, subconjunctival injection of cell wall mixed with complete Freund's adjuvant, topical application of cell wall to the eye, and topical application of viable S. aureus to the eye. All four immunization groups showed an IgG antibody response to ribitol teichoic acid in serum and tears with the highest titers in serum found after intradermal immunization with cell wall and the highest titers in tears found after topical application of S. aureus. All four immunization routes showed an IgA antibody response to ribitol teichoic acid in tears with the highest titers found after subconjunctival immunization with cell wall. There was no IgA response to ribitol teichoic acid in serum in any group. The results of this study suggest that ocular immune responses to S. aureus may be influenced by exposure to staphylococcal antigens not only in the external eye but also at sites remote from the eye.

Administration, Topical↗

PubMed1987

Corneal antibody levels to ribitol teichoic acid in rabbits immunized with staphylococcal antigens using various routes.

Although Staphylococcus aureus is an important cause of infectious diseases of the eye and hypersensitivity lesions of the cornea, little is known about ocular immunity to this pathogen. Using an enzyme-linked immunosorbent assay, we measured antibody titers to ribitol teichoic acid, the major antigenic determinant of S. aureus, in corneas as well as serum and tears after immunizing rabbits using the following routes: intradermal injection of cell wall mixed with complete Freund's adjuvant, subconjunctival injection of cell wall mixed with complete Freund's adjuvant, topical application of cell wall to the eye or topical application of viable S. aureus to the eye. IgG titers to ribitol teichoic acid were found consistently in corneas after intradermal and subconjunctival immunization with cell wall and topical immunization with viable S. aureus. After intradermal immunization with cell wall, IgG titers in cornea were higher than tears but lower than serum, which was presumably the source of the IgG antibodies for the cornea. After subconjunctival immunization with cell wall or topical immunization with viable S. aureus, IgG titers in corneas were higher than tears and generally higher than serum, suggesting that the ocular tissues were a local source of IgG. On the other hand, IgA titers to ribitol teichoic acid were found in tears but not in serum and were found only occasionally in corneas, suggesting that IgG responses to staphylococcal antigens may be more important than IgA responses in the cornea. The results of this study suggest that corneal antibodies to ribitol teichoic acid may be influenced by exposure to staphylococcal antigens not only in the external eye but also at sites remote from the eye.

Administration, Topical↗

PubMed1981

Polymorphonuclear neutrophil chemotaxis induced and inhibited by Bacteroides spp.

A possible virulence factor for Bacteroides subcutaneous abscesses has been found. The effect of Bacteroides culture filtrate and outer membrane on chemotaxis of rabbit peritoneal polymorphonuclear (PMN) neutrophils was assayed in Boyden chambers and via exocytosis of N-acetyl-beta-glucosaminidase. Both Bacteroides culture filtrate and outer membrane elicited some chemotaxis, as measured in the Boyden chamber; however, they had little effect upon exocytosis in cytochalasin B-treated PMN neutrophils. In the presence of serum complement, they completely abolished PMN neutrophil movement in the Boyden chamber assay, yet they gave a definite positive response for the exocytosis assay in the presence of serum complement or activated complement fragment.

Acetylglucosaminidase↗