Retinal safety of the irradiation delivered to light-adjustable intraocular lenses evaluated in a rabbit model.

PURPOSE: To evaluate the safety to the retina of a light-delivery device used to irradiate a light-adjustable intraocular lens (IOL) after implantation in a rabbit model. SETTING: John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. METHODS: In this study, rabbits had phacoemulsification with implantation of an ultraviolet (UV)-filtering light-adjustable IOL (study IOL) in 1 eye and a custom-made silicone IOL without a UV filter (control IOL) in the opposite eye. The study IOLs were irradiated at 1.0, 2.0, 3.0, and 5.0 times the expected maximum UV irradiation doses and the control IOLs, at 0.3, 0.6, 1.0, and 2.0 times. One week after irradiation, slitlamp and fundus (indirect ophthalmoscopy) examinations were performed. The rabbits were then humanely killed and their eyes enucleated and processed for histopathology. RESULTS: The 16 eyes with the study IOL (with UV filter) showed no signs of corneal, anterior segment, or retinal toxicity on histopathologic evaluation. The 16 eyes with the control IOL (no UV filter) also showed no signs of corneal or anterior segment toxicity; however, 3 eyes receiving the higher radiation doses had focal areas of retinal damage consistent with laser burn. CONCLUSION: Pigmented rabbit eyes with a light-adjustable IOL with a UV filter showed no signs of retina toxicity after near-UV light exposure up to 5 times the expected maximum treatment dosage. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned. Additional disclosures are found in the footnotes.

Uropathogenic Escherichia coli CFT073 is adapted to acetatogenic growth but does not require acetate during murine urinary tract infection.

In vivo accumulation of D-serine by Escherichia coli CFT073 leads to elevated expression of PAP fimbriae and hemolysin by an unknown mechanism. Loss of D-serine catabolism by CFT073 leads to a competitive advantage during murine urinary tract infection (UTI), but loss of both D- and L-serine catabolism results in attenuation. Serine is the first amino acid to be consumed in closed tryptone broth cultures and precedes the production of acetyl phosphate, a high-energy molecule involved in intracellular signaling, and the eventual secretion of acetate. We propose that the colonization defect associated with the loss of serine catabolism is due to perturbations of acetate metabolism. CFT073 grows more rapidly on acetogenic substrates than does E. coli K-12 isolate MG1655. As shown by transcription microarray results, D-serine is catabolized into acetate via the phosphotransacetylase (pta) and acetate kinase (ackA) genes while downregulating expression of acetyl coenzyme A synthase (acs). CFT073 acs, which is unable to reclaim secreted acetate, colonized mouse bladders and kidneys in the murine model of UTI indistinguishably from the wild type. Both pta and ackA are involved in the maintenance of intracellular acetyl phosphate. CFT073 pta and ackA mutants were screened to investigate the role of acetyl phosphate in UTI pathogenesis. Both single mutants are at a competitive disadvantage relative to the wild type in the kidneys but normally colonize the bladder. CFT073 ackA pta was attenuated in both the bladder and the kidneys. Thus, we demonstrate that CFT073 is adapted to acetate metabolism as a result of requiring a proper cycling of the acetyl phosphate pathway for colonization of the upper urinary tract.

Prevention of endophthalmitis by collagen shields presoaked in fourth-generation fluoroquinolones versus by topical prophylaxis.

PURPOSE: To compare the prophylaxis of collagen shields presoaked in antibiotics versus antibiotic drops after bacterial anterior chamber challenge. SETTING: John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. METHODS: Forty rabbits received bilateral 0.03 mL intracameral injections of Staphylococcus epidermidis (5 x 10(8) colony-forming units). Four groups of 10 rabbits had their eyes randomized to receive (1) 3 mg/mL gatifloxacin (Zymar) drops or shield in Zymar, (2) Zymar drops or shield in 10 mg/mL gatifloxacin (Tequin), (3) 5 mg/mL moxifloxacin (Vigamox) drops or shield in Vigamox, or (4) balanced salt solution (BSS) drops or shield in BSS. Each eye received Zymar, Vigamox, or BSS 4 times 1 hour before injection. The antibiotic-BSS was administered every 2 hours (5 doses total). One day later, signs of endophthalmitis were scored under the slitlamp. RESULTS: Groups 1 and 2 had significantly lower endophthalmitis incidences (total score > or = 8) than the BSS controls. Shield scores were not significantly different from those of the counterpart drops. The comparison between drops was not significant (P = .0513); the difference between shields (P = .0232) and the post-comparison Zymar versus BSS shields (P = .0021) were significant. CONCLUSIONS: Topical therapy with gatifloxacin before and after intraocular bacteria challenge led to lower incidences of endophthalmitis in rabbits. Prophylaxis with presoaked collagen shields was not statistically different than that with topical drops.

Roles of serine accumulation and catabolism in the colonization of the murine urinary tract by Escherichia coli CFT073.

A D-serine deaminase (DsdA) mutant of uropathogenic Escherichia coli strain CFT073 has a hypercolonization phenotype in a murine model of urinary tract infection (UTI) due to increased virulence gene expression by an unknown mechanism (B. J. Haugen et al., Infect. Immun. 75:278-289, 2007). DsdC is a D-serine-dependent activator of dsdXA transcription. DsdC may regulate the virulence genes responsible for hypercolonization. The loss of DsdA leads to increased intracellular accumulation of D-serine. In this study we show that deletion of the genes encoding L-serine deaminases SdaA and SdaB resulted in a mutant that accumulates higher intracellular levels of L-serine than CFT073. CFT073 sdaA sdaB has a mild competitive colonization defect whereas a CFT073 dsdA sdaA sdaB triple mutant shows a greater loss in competitive colonization ability. Thus, the inability to generate serine-specific catabolic products does not result in hypercolonization and the ability to catabolize serine represents a positive physiological trait during murine UTI. CFT073 dsdC and CFT073 dsdC dsdA mutants continue to outcompete the wild type in the UTI model. These results confirm that loss of DsdA activity results in the hypercolonization phenotype and that DsdC does not play a direct role in the elevated-colonization phenotype. Interestingly, a CFT073 dsdA mutant with deletions of D-serine transporter genes dsdX and cycA shows wild-type colonization levels of the bladder but is attenuated for kidney colonization. Thus, D-serine acts as a signal for hypercolonization and virulence gene expression by CFT073 dsdA, whereas overall catabolism of serine represents a positive Escherichia coli fitness trait during UTI.

Corneal endothelial safety with the irradiation system for light-adjustable intraocular lenses.

PURPOSE: To assess the safety to the corneal endothelium of the irradiation delivered through a system developed for noninvasive postoperative power adjustments of the Light Adjustable Lens (LAL) (Calhoun Vision). SETTING: John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. METHODS: After anesthesia, 12 cats had a light beam of near ultraviolet light (365 nm), with an intensity of 250 mW/cm(2), applied to the central 6.0 mm of the right cornea for 120 seconds. The cats were killed 1 day, 1 week, and 1 and 3 months after light application (3 cats/time point). Their corneas were then removed and evaluated for evidence of morphological damage to the corneal endothelial cells by staining with trypan blue and alizarin red and quantification with a digital imaging program (EPCO system). RESULTS: The overall size and shape of the corneal endothelial cells were qualitatively similar in irradiated and nonirradiated eyes. Four corneas in the irradiated group and 3 corneas in the control group had small areas of cell damage (staining with trypan blue) within the central 6.0 mm. These areas were generally close to corneal folds. The differences in damaged areas between both groups at each time point, as well as the difference considering the overall results in both groups, were not significant (P>.05). CONCLUSIONS: Irradiation of cat corneas with the therapeutic dose used to lock in the power of the LAL was not associated with damage to endothelial cells. Further studies are necessary to confirm the absence of damage at the ultrastructural level.

In vivo gene expression analysis identifies genes required for enhanced colonization of the mouse urinary tract by uropathogenic Escherichia coli strain CFT073 dsdA.

Deletional inactivation of the gene encoding d-serine deaminase, dsdA, in uropathogenic Escherichia coli strain CFT073 results in a hypermotile strain with a hypercolonization phenotype in the bladder and kidneys of mice in a model of urinary tract infection (UTI). The in vivo gene expression profiles of CFT073 and CFT073 dsdA were compared by isolating RNA directly from the urine of mice challenged with each strain individually. Hybridization of cDNAs derived from these samples to CFT073-specific microarrays allowed identification of genes that were up- or down-regulated in the dsdA deletion strain during UTI. Up-regulated genes included the known d-serine-responsive gene dsdX, suggesting in vivo intracellular accumulation of d-serine by CFT073 dsdA. Genes encoding F1C fimbriae, both copies of P fimbriae, hemolysin, OmpF, a dipeptide transporter DppA, a heat shock chaperone IbpB, and clusters of open reading frames with unknown functions were also up-regulated. To determine the role of these genes as well as motility in the hypercolonization phenotype, mutants were constructed in the CFT073 dsdA background and tested in competition against the wild type in the murine model of UTI. Strains with deletions of one or both of the two P fimbrial operons, hlyA, fliC, ibpB, c0468, locus c3566 to c3568, or c2485 to c2490 colonized mouse bladders and kidneys at levels indistinguishable from wild type. CFT073 dsdA c2398 and CFT073 dsdA focA maintained a hypercolonization phenotype. A CFT073 dsdA dppA mutant was attenuated 10- to 50-fold in its colonization ability compared to CFT073. Our results support a role for d-serine catabolism and signaling in global virulence gene regulation of uropathogenic E. coli.

New photochromic foldable intraocular lens: preliminary study of feasibility and biocompatibility.

PURPOSE: To evaluate a new hydrophobic acrylic intraocular lens (IOL) with photochromic properties in vitro and in vivo in a rabbit model. SETTING: John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. METHODS: The photochromic optic change of 5 study IOLs was evaluated in vitro on ultraviolet (UV) light exposure. The tests were done in the dry state and during immersion of the lenses in a balanced salt solution. Six additional IOLs were implanted in the right eye of New Zealand rabbits. The left eyes were implanted with SA60AT or SN60AT IOLs (Alcon Laboratories, 3 each). After a clinical follow-up of 6 months, the rabbits were killed and their eyes enucleated. Three study IOLs and 2 control SN60AT IOLs were evaluated in vitro on UV exposure after explantation. The other IOLs and the rabbit eyes had histopathologic examination. RESULTS: On in vitro UV light exposure, the optic of the study IOLs changed from colorless to yellow, turning again colorless on discontinuation of UV light projection. The same photochromic change was also observed on UV light exposure throughout the clinical follow-up of 6 rabbits, as well as after explantation of the IOLs. Postoperative clinical inflammatory reactions and cellular reactions on the surface of the explanted IOLs were similar in the study and control groups. No sign of untoward toxicity was observed in the histopathological sections of the rabbit eyes in all groups. CONCLUSIONS: The new photochromic IOL turned yellow only on exposure to UV light; otherwise it remained clear. This lens was also found to be biocompatible.

A light adjustable lens with injectable optics.

The light adjustable lens (LAL) is an innovative intraocular lens optic composed of partially polymerized macromers with an appropriately bonded photosensitizer. The injectable technology and multifocality associated with the LAL can produce precise refractive correction and, it is hoped, the type of accommodative range that is taken for granted during youth. Combining these technologies with a lens material that behaves like the crystalline lens of 25-year-old could precisely return near and distance vision to older adults.

A light adjustable lens with injectable optics.

PURPOSE OF REVIEW: Technology exists today that could permit refractive precision unheard of at the present time plus the correction of higher-order aberrations and restoration of accommodation in presbyopic adults. RECENT FINDINGS: With the light adjustable lens, after surgery, the shape of the lens can be customized to treat spherical, cylindrical and other higher-order aberrations. The posterior surface of the lens can be adjusted to create both refractive multifocality and diffractive bifocality. It can be made out of a variety of materials, some of which can be injected into the capsule, filling it, thus replicating the original shape of a crystalline lens. While the current technique of bag filling does permit the less viscous materials to leak out of the bag this is a solvable problem. For example, a disc can fill an ordinary-sized capsulorrhexis opening, allowing removal of the cataract using standard techniques and filling behind this disc. Also the material, once injected, could be polymerized. Posterior capsule opacification is also potentially solvable with devices that completely destroy lens epithelial cells or through a polymerization process of the new lens material in which the reaction destroys the capsular cells and actually binds to the capsule. SUMMARY: It is apparent that light adjustable lenses plus injectable technology, and multifocality can produce precise refractive correction and, hopefully, the type of accommodative range that we take for granted when we are young. Combining these technologies with a lens material that behaves like a crystalline lens of a 25 year old could precisely return near and distance vision to older adults.

Coordinate expression of fimbriae in uropathogenic Escherichia coli.

Uropathogenic Escherichia coli is the most common etiological agent of urinary tract infections. Bacteria can often express multiple adhesins during infection in order to favor attachment to specific niches within the urinary tract. We have recently demonstrated that type 1 fimbria, a phase-variable virulence factor involved in adherence, was the most highly expressed adhesin during urinary tract infection. Here, we examine whether the expression of type 1 fimbriae can affect the expression of other adhesins. Type 1 fimbrial phase-locked mutants of E. coli strain CFT073, which harbors genes for numerous adhesins, were employed in this study. CFT073-specific DNA microarray analysis of these strains demonstrates that the expression of type 1 fimbriae coordinately affects the expression of P fimbriae in an inverse manner. This represents evidence for direct communication between genes relating to pathogenesis, perhaps to aid the sequential occupation of different urinary tract tissues. While the role of type 1 fimbriae during infection has been clear, the role of P fimbriae must be further defined to assert the relevance of coordinated regulation in vivo. Therefore, we examined the ability of P fimbrial isogenic mutants, constructed in a type 1 fimbrial-negative background, to compete in the murine urinary tract over a period of 168 h. No differences in the colonization of these mutants were observed. However, comparison of these results with previous studies suggests that inversely coordinated expression of adhesin gene clusters does occur in vivo. Interestingly, the mutant that was incapable of expressing either type 1 or P fimbriae compensated by synthesizing F1C fimbriae.

Transcriptome of uropathogenic Escherichia coli during urinary tract infection.

A uropathogenic Escherichia coli strain CFT073-specific DNA microarray that includes each open reading frame was used to analyze the transcriptome of CFT073 bacteria isolated directly from the urine of infected CBA/J mice. The in vivo expression profiles were compared to that of E. coli CFT073 grown statically to exponential phase in rich medium, revealing the strategies this pathogen uses in vivo for colonization, growth, and survival in the urinary tract environment. The most highly expressed genes overall in vivo encoded translational machinery, indicating that the bacteria were in a rapid growth state despite specific nutrient limitations. Expression of type 1 fimbriae, a virulence factor involved in adherence, was highly upregulated in vivo. Five iron acquisition systems were all highly upregulated during urinary tract infection, as were genes responsible for capsular polysaccharide and lipopolysaccharide synthesis, drug resistance, and microcin secretion. Surprisingly, other fimbrial genes, such as pap and foc/sfa, and genes involved in motility and chemotaxis were downregulated in vivo. E. coli CFT073 grown in human urine resulted in the upregulation of iron acquisition, capsule, and microcin secretion genes, thus partially mimicking growth in vivo. On the basis of gene expression levels, the urinary tract appears to be nitrogen and iron limiting, of high osmolarity, and of moderate oxygenation. This study represents the first assessment of any E. coli pathotype's transcriptome in vivo and provides specific insights into the mechanisms necessary for urinary tract pathogenesis.

Uropathogenic Escherichia coli use d-serine deaminase to modulate infection of the murine urinary tract.

Although once thought to be unique to bacteria, d-amino acids are also produced by mammals. For example, d-serine is excreted in human urine at concentrations ranging from 3.0 to 40 micro g ml-1. An epidemiological survey demonstrated that urine isolates of E. coli are more likely to catabolise d-serine via expression of d-serine deaminase, DsdA than enteric disease isolates. The urosepsis strain, CFT073, and an isogenic dsdA mutant have similar growth kinetics in minimal or complex media. However, relative to the wild type, the dsdA mutant has a pleiomorphic cell shape and a prolonged, 4-6 h lag phase when grown in human urine. This suggests that d-serine catabolism provides a growth advantage in the urinary tract. Unexpectedly, in a direct competition model of urinary tract infection, the dsdA mutant was recovered 300-times more frequently than the wild type in the bladders of mice 48 h after infection. A new model of E. coli uropathogenesis is proposed where growth and gene expression are modulated in response to environmental d-serine levels. In support of this, the CFT073 dsdA mutant is hyperflagellated and more motile than the wild type indicating that intracellular levels of d-serine may directly or indirectly influence the expression of regulons associated with E. coli uropathogenesis.