Antimicrobial activity of topical dyes used in clinical veterinary ophthalmology.

OBJECTIVE: To evaluate in vitro the antibacterial effects of fluorescein, rose bengal, and lissamine green topical ophthalmic dyes against selected Gram-positive and Gram-negative bacteria, and to evaluate whether preserved or preservative-free fluorescein solutions are able to inhibit or potentiate bacterial growth. PROCEDURES: Susceptibility testing was performed using the Kirby-Bauer disk diffusion method plated with clinical ocular isolates of Staphylococcus aureus, Staphylococcus pseudintermedius, Streptococcus spp., Escherichia coli, and Pseudomonas aeruginosa. Bacterial growth inhibition was evaluated 24 hours following the addition of commercially available fluorescein, rose bengal, and lissamine green sterile strips. Antimicrobial effectiveness testing was performed by inoculation of compounded 1% dye solutions, both with and without preservatives (fluorescein and lissamine contained thiomersal, and rose bengal contained nipagin and nepazol), with the five previously mentioned bacteria. Growth was evaluated at days 7, 14, and 28. RESULTS: All dyes showed antibacterial activity against Gram-positive organisms. Preservative-free compounded 1% fluorescein solution inhibited growth of Gram-positive organisms but not of Gram-negative organisms. Preservative-free rose bengal and lissamine green inhibited growth of both types of organisms. CONCLUSIONS: Preferably, ocular surface samples for antimicrobial culture should be taken prior to the administration of topical dyes, due to their potential antibacterial activity, particularly if undiluted strips are applied directly or commercial fluorescein solutions are used and not immediately rinsed. Ophthalmic dye solutions containing preservative are safe from bacterial growth for up to 28 days if properly handled and stored. The use of preservative-free fluorescein solutions should be avoided and preservative-free rose bengal and lissamine green should be handled carefully.

The use of sulfur hexafluoride microbubbles for contrast-enhanced ocular ultrasonography of the pecten oculi in birds.

BACKGROUND: The pecten oculi is a vascular and pigmented structure localized within the posterior segment of all avian eyes. Its primary function is not fully understood yet. OBJECTIVE: As ultrasonography (US) is a useful imaging modality for evaluation of the pecten oculi, the objective of this study was to investigate the utility of an intravenous contrast solution of sulfur hexafluoride (SF6) microbubbles as a means of enhancing visualization of the pecten oculi in normal birds. ANIMALS STUDIED: Ten adult individuals of the following avian species were evaluated: 1 roadside hawk (Rupornis magnirostris), 1 stygian owl (Asio stygius), 2 striped owls (Asio clamator), 2 burrowing owls (Athene cunicularia), 2 ring-necked parakeet (Psittacula krameri), and 2 domestic chickens (Gallus gallus domesticus). PROCEDURE(S): After baseline ocular sonograms were obtained in sedated animals, 4.5 µg/kg of a contrast solution containing SF6 microbubbles was administered intravenously and US of the right eye was immediately performed. US was continued during injection to provide real-time imaging of the pecten oculi during vascular perfusion of contrast material. RESULTS: Within 2-3 seconds following intravenous contrast administration, microbubbles reached the pecten oculi of all birds investigated and provided significant ultrasonographic contrast enhancement. CONCLUSIONS: SF6 microbubble contrast ultrasonography in birds is a safe and easy procedure that provides increased contrast and enhanced visualization of the pecten oculi. Future use may enable further discovery of its physiologic functions and aid in the development of therapeutic plans for avian intraocular disease.

Schirmer's I, modified Schirmer's I, phenol red thread, and paper point tests: a comparative study for tear production measurement techniques in broiler chicks (Gallus gallus domesticus).

Problems with indoor husbandry and immunological challenges are some of the stressors that broilers may face which can affect production. Infectious diseases can compound the effects of excessive concentrations of ammonia causing respiratory and ocular inflammation and increased lacrimal production in broiler chickens. The objectives of this investigation were to establish normal values of tear production in chicks and compare the practicality of the different methods. Palpebral fissure length (PFL) and tear production were evaluated in Cobb 500 chicks at 5 d old and then at 5 d of age by the following methods: modified Schirmer's test I (mSTT1), phenol red cotton thread tear test (PRCTTT), and standardized endodontic absorbent paper point test (EAPPTT). Ten chicks at the age of 5 and 42 d were evaluated for each method. In addition, at 42 d, when the palpebral fissure permitted, a regular-sized Schirmer tear test I (STT1) was performed in another group of 10 chickens. Overall, PFL and the secretion of the aqueous phase of the tear film increased with age. Mean mSTT1 results were 5.00 ± 1.83 mm and 10.45 ± 2.58 mm for 5- and 42-d-old chicks, respectively. Mean PRCTTT results were 12.37 ± 1.80 mm and 25.58 ± 4.8 mm for 5- and 42-d-old chicks, respectively. Mean EAPPTT results were 7.13 ± 0.72 mm and 12.03 ± 0.92 mm for 5- and 42-d-old chicks, respectively. Mean STT1 for 42-d-old chicks was 11.40 ± 2.60 mm. Results obtained with endodontic paper points showed the lowest coefficient of variation and investigators found the test easier to perform. These values reported for broilers at different ages may be applied in poultry ophthalmology to help the diagnosis of lacrimal production disorders and to detect early disease symptoms that could cause economic losses in poultry production.