Deepinder K. Dhaliwal

Gatifloxacin and moxifloxacin: an in vitro susceptibility comparison to levofloxacin, ciprofloxacin, and ofloxacin using bacterial keratitis isolates

PURPOSE We compared the in vitro susceptibility patterns and the minimum inhibitory concentrations (MICs) of gatifloxacin (GAT) and moxifloxacin (MOX) (fourth-generation fluoroquinolones) to ciprofloxacin (CIP) and ofloxacin (OFX) (second-generation fluoroquinolones) and levofloxacin (LEV; third-generation fluoroquinolone) using bacterial keratitis isolates. The goal was to determine whether the fourth-generation fluoroquinolones offer any advantages over the second- and third-generation fluoroquinolones. DESIGN Experimental laboratory investigation. In contrast to an epidemiologic prevalence study, this study was designed to compare the relative susceptibility of each bacterial group to different fluoroquinolones by deliberate selection of representative isolates that were both susceptible and resistant to second-generation fluoroquinolones. METHODS In retrospect, the MICs of 177 bacterial keratitis isolates were determined to CIP, OFX, LEV, GAT, and MOX using E tests. A relative susceptibility analysis was performed for each bacterial group that included separate bacterial groups that were resistant to second-generation fluoroquinolones. The NCCLS susceptibility patterns and the MICs were compared statistically. Comparing MICs, the antibiotic with the lower MICs has greater antibacterial activity. RESULTS For most keratitis isolates, there were no susceptibility differences among the five fluoroquinolones. The fourth-generation fluoroquinolones did, however, demonstrate increased susceptibility for Staphylococcus aureus isolates that were resistant to CIP, LEV and OFX. In general, CIP demonstrated the lowest MICs for gram-negative bacteria. The MICs for fourth-generation fluoroquinolones were statistically lower than the second-generation fluoroquinolones for all gram-positive bacteria tested. Comparing the two fourth-generation fluoroquinolones, MOX demonstrated lower MICs for most gram-positive bacteria, whereas GAT demonstrated lower MICs for most gram-negative bacteria. CONCLUSIONS Based on in vitro testing, the fourth-generation fluoroquinolones may offer some advantages over those currently available for the treatment of bacterial keratitis. Clinical studies will be required to confirm these results.

Femtosecond laser-assisted cataract surgery.

Femtosecond laser-assisted cataract surgery provides surgeons an exciting new option to potentially improve patient outcomes and safety. Over the past 2 years, 4 unique laser platforms have been introduced into the marketplace. The introduction of this new technology has been accompanied by a host of new clinical, logistical, and financial challenges for surgeons. This article describes the evolution of femtosecond laser technology for use in cataract surgery. It reviews the available laser platforms and discusses the necessary modifications in cataract surgery technique and the logistics of incorporating a femtosecond laser into ones practice.

Antibiotic Resistance in the Treatment of Staphylococcus aureus Keratitis: A 20-Year Review

Purpose: We compared the resistance patterns of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible Staphylococcus aureus (MSSA) keratitis isolates with the common topically applied ophthalmic antimicrobials. Methods: We reviewed the antibiotic susceptibility results of 122 MRSA and 276 MSSA keratitis isolates from January 1993 to November 2012. In vitro susceptibility testing of each Staphylococcus aureus (SA) isolate was performed using Kirby–Bauer disk diffusion based on modified serum interpretations for cefoxitin, bacitracin, cefazolin, ciprofloxacin, gatifloxacin, gentamicin, moxifloxacin, ofloxacin, polymyxin B, sulfamethoxazole, tobramycin, and trimethoprim. Results: MRSA represented 30.7% (122 of 398) of the total SA isolates. All the SA isolates were susceptible to vancomycin, whereas they were less susceptible to the fluoroquinolones than to the nonfluoroquinolones. In comparison with MSSA, MRSA was significantly more resistant to all the antibiotics tested other than polymyxin B (both equally resistant) and vancomycin (both equally susceptible) (P < 0.001). Besides vancomycin, MRSA demonstrated the best susceptibilities to sulfamethoxazole (94.3%), bacitracin (89.3%), trimethoprim (88.5%), and gentamicin (86.1%). Additionally, MRSA was found to be significantly more resistant to the second-generation fluoroquinolones (ciprofloxacin and ofloxacin) than to the fourth-generation fluoroquinolones (moxifloxacin and gatifloxacin). An increase in resistance to the fourth-generation fluoroquinolones was detected for both MRSA and MSSA over the study period. Conclusions: The in vitro susceptibilities of commonly used topical antibiotics differ for MRSA and MSSA isolates; thus, successful treatment of bacterial keratitis should be supported with laboratory studies. Vancomycin remains the treatment of choice for MRSA keratitis. The empiric use of second-generation fluoroquinolones seems to be contraindicated in the treatment of MRSA keratitis.

Experimental laser-assisted in situ keratomileusis induces the reactivation of latent herpes simplex virus

PURPOSE We determined whether laser-assisted in situ keratomileusis acts as a trigger for the reactivation and ocular shedding of herpes simplex virus type-1 in a rabbit latency model. METHODS Herpes simplex virus type-1 latently infected rabbits were divided into three treatment groups: Group I received surface excimer laser ablation in both eyes (positive control), Group II received laser-assisted in situ keratomileusis in both eyes, and Group III received no treatment (negative control). Eyes were cultured daily for 10 days to determine herpes simplex virus type-1 reactivation. RESULTS The number of herpes simplex virus type-1 positive eye cultures and total herpes simplex virus type-1 shedding days were significantly greater after surface excimer laser ablation and laser-assisted in situ keratomileusis compared with the untreated control group (P < 0.002 and P < 0.000001, respectively). CONCLUSION Laser-assisted in situ keratomileusis as well as surface excimer laser ablation act as a trigger for the reactivation of herpes simplex virus type-1 in the rabbit latency model.

DNA cross-linking, double-strand breaks, and apoptosis in corneal endothelial cells after a single exposure to mitomycin C.

PURPOSE To investigate the cellular effects of mitomycin C (MMC) treatment on corneal endothelial (CE) cells at clinically relevant applications and dosages. METHODS Radial and posterior diffusion of MMC was determined by an Escherichia coli growth inhibition bioassay. A modified version of the comet assay (single cell gel electrophoresis) was used to detect DNA cross-linking. Immunostaining detected the nuclear phosphorylated histone variant H2AX (gamma-H2AX) indicating DNA double-strand breaks. Apoptosis in MMC-treated cells was detected with annexin V staining. RESULTS Topical application of 0.02% MMC to intact goat globes resulted in MMC in the CE at 0.37 microg/mL and produced a significant increase in CE DNA cross-linking with as little as 6 seconds of topical MMC treatment. DNA cross-linking was also demonstrated in cultured CE cells by using MMC exposures similar to those detected in CE of intact eyes. Such MMC treatment of CE produced elevated and persistent gamma-H2AX-positive cells indicative of DNA double-strand breaks. Similarly, there was an increase in the proportion of apoptotic CE cells, evidenced by positive annexin V staining. CONCLUSIONS The results demonstrate that exposure to MMC at times and concentrations commonly used in refractive surgery produces cross-linking of corneal endothelial DNA, persistent DNA damage, and endothelial death via apoptosis. Current practices of MMC application during refractive surgeries may increase the potential for long-term and permanent deleterious effects on the health of the corneal endothelium.

Valacyclovir inhibition of recovery of ocular herpes simplex virus type 1 after experimental reactivation by laser in situ keratomileusis

Purpose: To determine whether the systemic administration of valacyclovir (Valtrex®) reduces ocular shedding of herpes simplex virus type 1 (HSV‐1) after laser in situ keratomileusis (LASIK) in the New Zealand White (NZW) rabbit latency model. Setting: Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA. Methods: New Zealand White rabbits latently infected with HSV‐1 W strain were divided into 3 groups. The first received 100 mg/kg/day of valacyclovir; the second, 200 mg/kg/day of valacyclovir; and the third (control), saline. One half the total dose of valacyclovir was delivered via intraperitoneal injections twice daily for 7 days beginning with 1 dose before LASIK. The HSV‐1 ocular shedding was determined from eye cultures for 7 days after LASIK. Results: The administration of both 100 mg/kg/day and 200 mg/kg/day of valacyclovir significantly reduced the number of eyes (1/16 in both groups) and the total number of HSV‐1 shedding days (1/122 and 2/122, respectively) from which HSV‐1 was recovered compared to the control group (7/16 [P = .0396] and 14/129 [P < .007], respectively). Conclusions: Systemic administration of valacyclovir significantly reduced HSV‐1 ocular shedding after LASIK in the NZW rabbit latency model. The clinical implications of this study suggest that patients with a history of recurrent ocular herpes may be able to safely have LASIK with less risk of a recurrent herpetic episode while on valacyclovir antiviral prophylaxis.

Efficient reactivation of latent herpes simplex virus type 1 infection by excimer laser keratectomy in the experimental rabbit ocular model

PURPOSE To investigate the role of excimer laser keratectomy as a trigger for the reactivation of latent HSV type 1 (HSV-1) in the New Zealand rabbit ocular model. There are conflicting reports in the current literature about reactivation of HSV-1 after excimer laser photoablation. METHODS New Zealand rabbits were inoculated topically with HSV-1 McKrae or W strain in each eye, and culture-positive dendritic keratitis was documented on day 7. After the establishment of latency (21+ days), animals were divided into three groups: group I animals underwent excimer laser photoablation in each eye; group II animals received intrastromal injections of sterile water to act as positive controls (a standard method); and group III animals received no treatment and represented spontaneous shedders. All eyes were swabbed daily from days 1 through 10 and plated on A549 cells. Recovery of HSV-1 on days 1 through 10 postinduction was analyzed to compare the efficiency of the different methods of viral reactivation. RESULTS Reactivation of latent HSV-1 after excimer treatment was observed in nine (45%) of 20 eyes and was equivalent to the rate of reactivation seen in the positive control animals (eight [44.4%] of 18 eyes) (P=.99). Both of these rates were significantly greater than those of the untreated animals (one [5.6%] of 18 eyes) (P=.018). CONCLUSION Excimer laser keratectomy appears to be an efficient trigger for the reactivation of latent HSV-1 in the New Zealand rabbit ocular model.

Ocular bacterial infections: current and future treatment options

In this article, common ocular bacterial infections are reviewed, examining bacterial pathogens, antibiotics and antibacterial resistant trends in light of current and future treatment options. Ophthalmologists are fortunate to be able to choose between an array of old and new antibiotics in order to treat bacterial ocular infections. Ophthalmic infections are primarily treated with topical antibiotics applied directly to the eye. Since there are no in vitro susceptibility standards for interpreting ocular bacterial susceptibility, systemic standards are used. There is no immediate need for new ophthalmic antibiotics, but increasing resistance is being seen with the widely used fluoroquinolone antibiotics.

Pellucid Marginal Degeneration with Superior Corneal Thinning

PURPOSE Pellucid marginal degeneration is a noninflammatory thinning disorder typically involving the inferior cornea. We describe a patient with superior corneal thinning similar to classic pellucid marginal degeneration. METHODS An 80-year-old man was evaluated for high astigmatism. RESULTS The right superior cornea had a prominent band of thinning with ectasia. Both inferior corneas had characteristic zones of thinning without inflammation. CONCLUSIONS Superior pellucid marginal corneal degeneration should be considered in the differential diagnosis of superior corneal ectatic disorders.

In vitro comparison of ciprofloxacin, ofloxacin, and povidone-iodine for surgical prophylaxis.

used to dilate the pupil and capsulorhexis, along with a tenting effect of the iris and capsulorhexis. We did not encounter slippage of the flexible iris retractors during phacoemulsification as the surgery was performed by an experienced surgeon and we agree with Bloom et al. that this may be the problem in the learning curve. We encountered entanglement of soft cortical fibers in the edges of the nylon hooks, and recommend caution while aspirating these fibers. We believe that the endocapsular ring inserted prior to the hydroprocedures and phacoemulsification prevents the floppy equatorial capsule from prolapsing into the recess in the area of the compromised zonules. Thus, the 2 methods of capsule stabilization, ie, endocapsular ring and microhooks, are complementary and may be used simultaneously with success in cases with compromised zonules.