Comparative toxicity of preservatives on immortalized corneal and conjunctival epithelial cells.

PURPOSE: Nearly all eye drops contain preservatives to decrease contamination. Nonpreservatives such as disodium-ethylene diamine tetra-acetate (EDTA) and phosphate-buffered saline are also regularly added as buffering agents. These components can add to the toxicity of eye drops and cause ocular surface disease. To evaluate the potential toxicity of these common components and their comparative effects on the ocular surface, a tissue culture model utilizing immortalized corneal and conjunctival epithelial cells was utilized. METHODS: Immortalized human conjunctival and corneal epithelial cells were grown. At confluency, medium was replaced with 100 microL of varying concentrations of preservatives: benzalkonium chloride (BAK), methyl paraben (MP), sodium perborate (SP), chlorobutanol (Cbl), and stabilized thimerosal (Thi); varying concentrations of buffer: EDTA; media (viable control); and formalin (dead control). After 1 h, solutions were replaced with 150 microL of MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazonium bromide). After 4 h, solutions decanted, 100 microL of acid isopropanol added, and the optical density determined at 572 nm to evaluate cell viability. RESULTS: Conjunctival and corneal cell toxicity was seen with all preservatives. Depending upon concentration, BAK exhibited from 56% to 89% toxicity. In comparison, Cbl exhibited from 50% to 86%, MP from 30% to 76%, SP from 23% to 59%, and Thi from 70% to 95%. EDTA with minimal toxicity (from 6% to 59%) was indistinguishable from SP. CONCLUSIONS: Generally, the order of decreasing toxicity at the most commonly used concentrations: Thi (0.0025%) > BAK (0.025%) > Cbl (0.25%) > MP (0.01%) > SP (0.0025%) approximately EDTA (0.01%). Even at low concentration, these agents will cause some degree of ocular tissue damage.

Evaluation of toxicity of commercial ophthalmic fluoroquinolone antibiotics as assessed on immortalized corneal and conjunctival epithelial cells.

PURPOSE: To evaluate the toxicity of a variety of the fluoroquinolone antibiotics on the ocular surface by using tissue culture models of corneal epithelial cells and conjunctival epithelial cells. METHODS: Immortalized conjunctival (CCC) and human corneal (HCE) epithelial cells were grown and when confluent the cells allowed to air dry for 1 hour. Medium was then replaced with 100 microL of one of the following: 1) Vigamox [moxifloxacin (0.5%: MX)]; (2) Zymar [gatifloxacin (0.3%: GA)]; 3) Quixin [levofloxacin (0.5%: LE)]; 4) Ocuflox [ofloxacin (0.3%: OF)]; 5) Ciloxan [ciprofloxacin (0.3%: CP)]; 6) medium (viable control); 7) "normal"/physiologic saline; 8) formalin (dead control). After one hour, 150 microL of MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazonium bromide was added and incubated for 4 hours. After decanting, precipitate was dissolved in 150 microL of isopropanol. Absorbance was determined at 572 nm. RESULTS: The lowest amount of cell death was associated with the viable control. All ophthalmic preparations showed both corneal and conjunctival cell toxicity. Aside from the viable control, normal saline showed the next lowest amount of toxicity. Of the topical ocular antibiotics tested, MX showed the least amount of toxicity. All of the other antibiotics tested were statistically indistinguishable from each other. CONCLUSIONS: All of the topical ocular antibiotics tested showed evidence of both corneal and conjunctival toxicity (MX < OF < or = LE < or = CP < or = GA), although only MX was statistically significant. Whether this finding reflects on in vivo wound healing remains to be determined. This model provides a rapid and cost-effective method to screen for surface toxicity of topical agents.

Susceptibility testing of clinical isolates of pseudomonas aeruginosa to levofloxacin, moxifloxacin, and gatifloxacin as a guide to treating pseudomonas ocular infections.

PURPOSE: Pseudomonas aeruginosa ocular infections most frequently originate from an environmental source; successful treatment with various ocular antibiotics is well established. However, emergence of resistant clones to available antibiotics poses a real threat to successful treatment. The purpose of this study was to evaluate the antibiotic susceptibilities of 100 random clinical isolates of P. aeruginosa to levofloxacin, moxifloxacin, and gatifloxacin, potential agents for the treatment of ocular infections caused by this microorganism. METHODS: One hundred consecutive strains of P. aeruginosa were isolated from clinical specimens submitted to the clinical microbiology hospital laboratory. Duplicate isolates were not included. The minimum inhibitory concentrations (MICs) of these isolates were determined by using Etests, performed according to the manufacturer's instructions. American Type Culture Collection (ATCC) strains of Escherichia coli, P. aeruginosa, and Staphylococcus aureus served as reference controls. RESULTS: Although most isolates were susceptible to levofloxacin, moxifloxacin, and gatifloxacin and the MICs were not significantly different, significant numbers were resistant. The standardized controls rendered expected MICs. The susceptibility of the isolates varied with regard to source, and resistant strains showed increased resistance. CONCLUSIONS: Based on the data, the treatment of ocular infections caused by P. aeruginosa with levofloxacin, moxifloxacin, and gatifloxacin still has a high likelihood of success. However, six of the isolates collected were resistant to all three of the fluoroquinolones tested. Based on the data, clinicians must be aware that clinical resistance can occur even with the newer fluoroquinolones.