Topical levofloxacin 1.5% overcomes in vitro resistance in rabbit keratitis models.

PURPOSE: To determine whether topical levofloxacin 1.5% will successfully treat both levofloxacin-resistant and susceptible Staphylococcus aureus (SA) and Pseudomonas aeruginosa (PA) in rabbit keratitis models. METHODS: For levofloxacin-resistant and susceptible SA, respectively, 32 New Zealand White (NZW) rabbits were intrastromally injected with 1000 colony-forming units (CFU). After 4 hr, the corneas of eight rabbits were homogenized to determine onset CFU/ml. Twenty-four rabbits were divided into three treatments: levofloxacin, vancomycin (cefazolin for levofloxacin-susceptible SA) and saline. Twenty-one drops were administered over 5 hr. One hour post-treatment, the corneas were homogenized for CFU/ml. For levofloxacin-resistant and susceptible PA, respectively, 32 NZW rabbits were intrastromally injected with 1000 CFU. After 16 hr, the corneas of eight rabbits were homogenized for CFU/ml. Twenty-four rabbits were divided into three treatments: levofloxacin, tobramycin (ciprofloxacin for levofloxacin-susceptible PA) and saline. Nineteen drops were administered over 8 hr. One hour post-treatment, the corneas were homogenized for CFU/ml. The CFU/ml data were analysed for sterilization and non-parametrically for reduction. RESULTS: Levofloxacin 1.5% significantly reduced more (p < 0.05) levofloxacin-resistant SA than vancomycin; was equivalent to cefazolin (p > 0.05) for levofloxacin-susceptible SA; was equivalent to tobramycin for levofloxacin-resistant PA; was equivalent to ciprofloxacin for levofloxacin-susceptible PA; and significantly reduced more SA and PA than saline and onset. Levofloxacin 1.5% sterilized the corneas in the levofloxacin-resistant and susceptible PA groups (32/32) and levofloxacin-susceptible SA group (16/16), but not the levofloxacin-resistant SA group (0/16). CONCLUSION: Levofloxacin 1.5% was effective for reducing SA and PA in the rabbit keratitis models regardless of in vitro resistance.

A comparison of moxifloxacin and levofloxacin topical prophylaxis in a fluoroquinolone-resistant Staphylococcus aureus rabbit model.

PURPOSE: Moxifloxacin, a fourth-generation fluoroquinolone (FQ), was compared to levofloxacin, a third-generation FQ, for preventing FQ-resistant, methicillin-resistant Staphylococcus aureus (FQrMRSA) endophthalmitis in a rabbit model. METHODS: Three regimens of topical treatments (moxifloxacin 0.5%, levofloxacin 0.5%, and saline) were tested to prevent endophthalmitis. For each regimen, drops were instilled every 15 min for 1 h into the left eyes of 15 rabbits. After anesthesia, 2 x 10(4) cfu of FQrMRSA was injected into the aqueous. One drop of treatment was given immediately, and another four drops were applied over 24 h. At 24 h, the eyes were clinically graded for endophthalmitis. After the rabbits were sacrificed, the aqueous and vitreous were tapped for bacterial colony counts. RESULTS: Topical moxifloxacin (12/15, 80%) significantly (P=0.0001) prevented clinical endophthalmitis in more rabbits than levofloxacin (2/15, 13%) or saline (2/15, 13%). The total median clinical score for moxifloxacin treatment (1.0) was significantly (P=0.0004) lower than that for levofloxacin (20.0) or saline (23.0). Culture-negative eyes were less frequent for levofloxacin (8/15, 53%) and saline (1/15, 7%) treatments than for moxifloxacin treatment (12/15, 80%). CONCLUSION: This in vivo study indicates that moxifloxacin, a fourth-generation FQ, may be more effective than levofloxacin, a third-generation FQ, in preventing experimental FQrMRSA. endophthalmitis.

The disinfection of contact lenses contaminated with adenovirus.

PURPOSE: We compared the efficacy of different contact lens disinfection systems to eliminate adenovirus. METHODS: Laboratory study evaluating the elimination of adenoviral ocular isolates by contact lens disinfection systems. Hard (gas permeable) and soft contact lenses were contaminated with adenovirus serotypes 8 and 19, and then they were disinfected with chemical, hydrogen peroxide, and heat sterilization systems. The survival of the adenovirus was determined by the shell vial technique. RESULTS: Adenovirus survived chemical and hydrogen peroxide disinfection but not heat sterilization. CONCLUSION: Because heat sterilization is not readily available to sterilize adenovirus contaminated contact lenses, it may be prudent for patients with adenoviral keratoconjunctivitis to dispose of unclean contact lenses.

An in vitro resistance study of levofloxacin, ciprofloxacin, and ofloxacin using keratitis isolates of Staphylococcus aureus and Pseudomonas aeruginosa.

PURPOSE: We compared levofloxacin with ciprofloxacin and ofloxacin using the in vitro susceptibilities of Staphylococcus aureus (SA) and Pseudomonas aeruginosa (PA) keratitis isolates. DESIGN: Retrospective, clinical laboratory study of antibiotic susceptibility among keratitis isolates. PARTICIPANTS: Keratitis isolates from 200 patients with either SA or PA keratitis. METHODS: Minimum inhibitory concentrations (MICs) were determined for levofloxacin, ofloxacin, and ciprofloxacin for 93 SA keratitis isolates (68 fluoroquinolone-resistant and 25 susceptible, as determined by disk diffusion) and 107 PA keratitis isolates (13 fluoroquinolone-resistant and 94 susceptible). National Committee for Clinical Laboratory Standards susceptibilities were determined and analyzed statistically. Time kill studies were determined for fluoroquinolone-susceptible and -resistant isolates to all antibiotics at 8 microg/ml. The killing rates were determined by regression, and the colony count decreases were analyzed. MAIN OUTCOME MEASURES: The susceptibilities and potencies of levofloxacin, ciprofloxacin, and ofloxacin to SA and PA were determined from the MICs. Time kill studies determined the killing rates and decreases in colony counts. RESULTS: The fluoroquinolone-resistant SA susceptibilities to levofloxacin, ofloxacin, and ciprofloxacin were only 22%, 10%, and 3%, respectively. The fluoroquinolone-susceptible SA were 100% susceptible to all antibiotics, with levofloxacin demonstrating the best potency. The fluoroquinolone-resistant PA were resistant to all antibiotics. The fluoroquinolone-susceptible PA isolates were highly susceptible to levofloxacin, ofloxacin, and ciprofloxacin, with ciprofloxacin demonstrating the highest potency. For fluoroquinolone-susceptible SA and PA, the time kill studies determined that the killing rates and decreases in colony counts were equivalent for all three antibiotics tested. The time kill studies demonstrated no colony count decreases for the fluoroquinolone-resistant SA and PA. CONCLUSIONS: Taken together, our susceptibility and time kill data failed to demonstrate convincing differences in the susceptibility of SA and PA keratitis isolates to levofloxacin, ciprofloxacin, and ofloxacin. In general, bacterial isolates that were resistant to ciprofloxacin and ofloxacin were also resistant to levofloxacin.

Antiviral prophylaxis with twice daily topical cidofovir protects against challenge in the adenovirus type 5/New Zealand rabbit ocular model.

Adenoviral ocular infections are the most common external ocular infections world wide and there is no approved treatment. Topical cidofovir has been shown to be effective in vitro, in animal models and in case studies for the treatment of adenoviral ocular infections. Prophylaxis to prevent transmission within households and to reduce community epidemics remains an important public health goal. The current study examined whether antiviral prophylaxis with cidofovir, twice daily dosing, would restrict viral replication following a large challenge inoculum of adenovirus type 5 (Ad5) in the New Zealand white rabbit ocular model. The results showed that antiviral prophylaxis with 1 and 0.5% cidofovir significantly reduced mean daily Ad5 ocular titers (days 0-5), the number of Ad5 positive cultures/total (days 1-14), serial Ad5 positive cultures/total (days 1, 2, 3, 4, 5, 7), and the number of eyes with Ad5 replication beyond day 0 (1% cidofovir only). Antiviral prophylaxis appears to be an effective strategy to reduce and restrict adenovirus replication experimentally.

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.

Short-term treatment With a potent topical corticosteroid of an acute ocular adenoviral infection in the New Zealand white rabbit.

PURPOSE: To determine the effect of short-term topical therapy with 1% prednisolone acetate (PA) on normal immune adenoviral clearance in the rabbit ocular model. METHODS: Thirty rabbits were topically inoculated in both eyes with adenovirus type 5 (Ad5). On day 1, the rabbits were divided into three topical treatment groups: 1% PA four times daily for 3 days, 1% PA four times daily for 5 days, control (artificial tears) four times daily for 5 days. Eyes were cultured for virus on days 0, 1, 3, 4, 5, 7, 9, 11, and 14. RESULTS: Compared with the control group, treatment with 1% PA for 3 or 5 days significantly increased the total and daily number of Ad5-positive cultures from days 7 to 14, prolonged the duration of Ad5 shedding, and increased the mean combined Ad5 titer from days 1 to 5. In addition, treatment with 1% PA for 5 days increased the mean combined Ad5 titer from days 7 to 14. CONCLUSION: Treatment of an ocular adenoviral infection with 1% PA for as little as four times daily for 3 days significantly enhanced adenoviral replication compared with the control group. Short-term corticosteroid treatment of acute adenoviral ocular infections with 1% PA should be used judiciously.

The antiviral resistance and replication of cidofovir-resistant adenovirus variants in the New Zealand White rabbit ocular model.

PURPOSE: To determine the antiviral resistance of three cidofovir (CDV)-resistant variants of adenovirus type 5 (Ad5) and their ability to replicate in the New Zealand White rabbit ocular model. METHODS: Rabbits were inoculated topically in both eyes with the CDV-resistant variants R1, R2, and R3, and the Ad5 parental strain. On day 1, rabbits from each virus inoculation were divided into two topical treatment groups: 0.5% CDV and PBS control. Treatment was administered twice daily in both eyes for 7 days. All eyes were cultured for virus on days 0, 1, 3, 4, 5, 7, 9, 11, and 14. Using viral outcome parameters, CDV resistance was determined for each virus by comparing each CDV-treated virus group to its respective PBS control, and altered pathogenesis was assessed by comparing viral replication in the PBS control groups of the Ad5 parent and the three resistant variants. RESULTS: Topical 0.5% CDV treatment demonstrated significant antiviral inhibitory activity in the Ad5 parental group (e.g., reduced total Ad5-positive cultures, reduced daily Ad5-positive cultures on days 5, 9, 11, and 14, and duration of ocular shedding), but had no effect on the three CDV-resistant variants. There were no significant differences in pathogenicity between the Ad5 parent and the CDV-resistant variants. CONCLUSIONS: The Ad5 variants R1, R2, and R3 were resistant to topical treatment with 0.5% cidofovir in the rabbit ocular model. However, the acquisition of CDV resistance did not alter the replication of the three Ad5 CDV variants on the rabbit eye.

Lomefloxacin is an effective treatment of experimental bacterial keratitis.

PURPOSE: Lomefloxacin was evaluated as a potential topical therapy for bacterial keratitis. METHODS: Lomefloxacin was compared with ciprofloxacin in different rabbit keratitis models. A total of 216 corneas were infected with Staphylococcus aureus (ciprofloxacin-susceptible and -resistant), Streptococcus viridans, Streptococcus pneumoniae, Pseudomonas aeruginosa, and Serratia marcescens and were treated with lomefloxacin (0.3%), ciprofloxacin (0.3% Ciloxan), and the control phosphate-buffered saline (PBS), respectively. The data were analyzed statistically comparing the decrease in the number of recovered viable bacteria. RESULTS: Compared with PBS-treated control corneas, the colony counts for all bacterial isolates were significantly reduced (p < 0.05) after topical treatment with either lomefloxacin or ciprofloxacin. For gram-positive bacteria, lomefloxacin and ciprofloxacin were equally effective. For gram-negative bacteria, lomefloxacin, while effective, was less so than ciprofloxacin under experimental conditions (p < 0.05). CONCLUSION: Our data, using multiple bacterial keratitis models, suggest that lomefloxacin is promising for therapy of bacterial keratitis. Further clinical studies are needed to expand its use for keratitis therapy.

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.

Vancomycin prophylaxis and emerging resistance: are ophthalmologists the villains? The heroes?

PURPOSE: To determine whether the routine use of vancomycin prophylaxis in elective cataract surgery promotes emerging resistance and provides effective protection against post-operative endophthalmitis. METHODS: Critical review of the current scientific and clinical literature was undertaken including appropriate statistical analyses of published data. RESULTS: Public health concerns for emergent vancomycin-resistant life-threatening "super bugs" are legitimate. Evaluation of the risk factors that are known to promote emerging vancomycin resistance (sick patients, hospital intensive care unit setting, methicillin-resistant Staphylococcus aureus (MRSA) clonal infections, prolonged systemic therapy, sub-therapeutic dosing, indwelling intravascular and drainage catheters, total kilogram usage and agricultural use) suggest that ophthalmic usage in routine cataract surgery is unlikely to be a significant factor in promoting emerging worldwide resistance. Clinical and scientific studies purporting to prove the value of vancomycin prophylaxis in cataract surgery contain substantial biases and design flaws that seriously undermine their validity. Issues of potential intraocular toxicity, increased costs, absence of medical-legal protection, and compliance with current Centers for Disease Control and Prevention (CDC) and American Academy of Ophthalmology guidelines (in hospital) mitigate against this practice. CONCLUSIONS: Ophthalmologists who use vancomycin prophylaxis in routine cataract surgery are neither the villains nor heroes according to my interpretation of the currently available scientific data. Personal conscience and an ongoing critical review of the literature should guide each ophthalmologist's choice in this controversy.

Effects of diclofenac or ketorolac on the inhibitory activity of cidofovir in the Ad5/NZW rabbit model.

PURPOSE: The goal of this study was to determine the effects of concurrent therapy with nonsteroidal anti-inflammatory drugs (NSAIDs) on the antiviral activity of cidofovir on adenovirus replication and the formation of subepithelial infiltrates in the Ad5/New Zealand White rabbit ocular model. METHODS: According to two protocols, 20 rabbits were inoculated in both eyes with Ad5 topically to study adenovirus replication, and 20 rabbits were inoculated in both eyes topically and intrastromally to study the formation of subepithelial infiltrates. Animals were randomized to four masked treatment groups: group I, 0.5% cidofovir + artificial tears; group II, 0.5% cidofovir + 0.5% ketorolac tromethamine; group III, 0.5% cidofovir + 0.1% diclofenac sodium; and group IV, control + artificial tears. Cidofovir and control were administered to both eyes twice daily for 7 days, and artificial tears, ketorolac, and diclofenac four times daily for 14 days. Eyes were cultured on days 0, 1, 3, 4, 5, 7, 9, 11, and 14. RESULTS: Compared with the control group, all cidofovir-treated groups demonstrated significant antiviral effects on adenovirus replication. There were no differences in adenovirus replication among the cidofovir-treated groups (I, II, and III), nor were there any differences among all groups (I-IV) in the formation of subepithelial infiltrates. CONCLUSIONS: Concurrent treatment of ketorolac or diclofenac with cidofovir did not diminish its antiviral inhibitory activity on adenovirus replication, nor did it prevent the formation of subepithelial infiltrates in the rabbit model.

The evolution of antiviral therapy for external ocular viral infections over twenty-five years.

PURPOSE: To review the past 25 years of the evolution of antiviral therapy for the treatment of common external ocular viral infections (herpes simplex virus type 1, varicella-zoster virus, and adenovirus). METHODS: A broad-based literature review in the fields of virology, antiviral research, and ophthalmology will be carried out. The pathogenesis of the major external ocular viral infections and history of antiviral development will be cited. Important conceptual breakthroughs as well as historical landmarks will be emphasized. RESULTS: The successful development of effective antivirals to treat the most common external ocular viral infections have dramatically reduced morbidity and sight loss. The immune pathogenesis of herpetic stromal keratitis is better understood. CONCLUSIONS: Remarkable progress in the development of antiviral therapy has occurred over the past quarter century. Future needs include improved antivirals and immunomodulators and vaccines to prevent and treat herpetic ocular infections and adenovirus keratoconjunctivitis.

Efficacy of topical cidofovir on multiple adenoviral serotypes in the New Zealand rabbit ocular model.

PURPOSE: The goal of the present study was to determine the efficacy of topical 0.5% cidofovir twice daily for 7 days on the replication of multiple adenovirus (Ad) serotypes of subgroup C (Ad1, Ad5, Ad6) in the New Zealand rabbit ocular model. METHODS: In duplicate experiments for each serotype, a total of 20 rabbits (Ad5) or 16 rabbits each (Ad1 and Ad6) were inoculated topically in both eyes, with 1.5 X 10(6) pfu/eye of the appropriate virus. Twenty-four hours later, the rabbits in each serotype group were randomly divided into two topical treatment groups: I, 0.5% cidofovir; II, control vehicle. Treatment was twice daily for 7 days. All eyes were cultured for virus on days 0, 1, 3, 4, 5, 7, 9, 11, and 14. RESULTS: Compared to the control, treatment with 0.5% cidofovir reduced the following: mean Ad titer (days 1 to 7) for Ad1 (6.3 +/- 20 x 10(1) versus 2.5 +/- 3.9 X 102 pfu/ml; P < 0.0003), Ad5 (3.4 +/-5.8 x 102 versus 1.6 +/- 2.0 x 10(3) pfu/ml; P < 0.000001), and Ad6 (1.2 +/- 5.1 x 10(2) versus 5.5 +/-14 x 10(2) pfu/ml; P = 0.015); reduced Ad-positive eyes/total for Adl [45/128 (35%) versus 84/128 (66%); P = 0.000002], Ad5 [84/160 (53%) versus 131/152 (86%); P < 0.000001], and Ad6 [36/128 (28%) versus 82/128 (64%); P < 0.000001]: and reduced the duration of Ad shedding forAdl (4.9 +/-1.9 versus 9.3 +/- 3.3 days; P < 0.00007), Ad5 (6.4 +/- 2.8 versus 11.5 +/- 2.3 days; P < 0.0001), and Ad6 (4.4 +/- 2.1 versus 8.4 +/- 2.5 days; P < 0.00004). CONCLUSIONS: Topical 0.5% cidofovir twice daily for 7 days demonstrated significant antiviral activity against multiple adenoviral serotypes (Ad1, Ad5, and Ad6) in the New Zealand rabbit ocular model. These in vivo data expand in vitro studies indicating the efficacy of cidofovir against different adenovirus serotypes and support its use in clinical trials.

Valacyclovir inhibits recovery of ocular HSV-1 after experimental reactivation by excimer laser keratectomy.

PURPOSE: The goal of this was to determine whether the systemic administration of valacyclovir (Valtrex) would reduce ocular shedding of herpes simplex virus 1 (HSV-1) after excimer laser ablation in the New Zealand rabbit latency model. METHODS: The in vitro 50% inhibitory concentration (IC50) of HSV-1 W strain was determined by using a plaque-reduction assay to verify its sensitivity to acyclovir. Forty-seven NZW rabbits latently infected with HSV-1 W strain were divided into four groups: I, 50 mg/kg/day valacyclovir; II, 100 mg/kg/day valacyclovir; III, 150 mg/kg/day valacyclovir; and IV, saline control. One half of the total dose of valacyclovir was delivered via intraperitoneal injections twice daily for 7 days beginning with one dose before excimer laser keratectomy. HSV-1 ocular shedding was determined from eye cultures for 7 days after treatment. RESULTS: The IC50 for HSV-1 W was determined to be 2.9 microg/ml. The administration of both 100 mg/kg/day (group II) and 150 mg/kg/day (group III) of valacyclovir significantly reduced the number of eyes from which latent HSV-1 was recovered compared with the control group. There was no difference between the control group and group I (50 mg/kg/day valacyclovir). However, all three valacyclovir dosages significantly reduced the total number of HSV-1 shedding days compared with the control group, and 100% HSV-1 TG latency was demonstrated for all four groups. CONCLUSION: Systemic administration of valacyclovir significantly reduced HSV-1 ocular shedding in a dose-dependent manner after excimer laser keratectomy in the NZW rabbit latency model.

The survival of herpes simplex virus in multidose office ophthalmic solutions.

PURPOSE: To determine the survival of herpes simplex virus type 1 (HSV-1) in several multidose ophthalmic solutions. METHODS: In three separate trials, 10 aliquots of 5 ml each of three common multidose topical ophthalmic solutions, sodium fluorescein, proparacaine, and nonpreserved artificial tears, were inoculated with 10(5), 10(4), and 10(3) pfu per ml of HSV-1. All samples were titered on A549 cells at various time points for surviving HSV-1. RESULTS: Herpes simplex virus type 1 was not recovered from the fluorescein and proparacaine solutions at 1 hour or any time thereafter, regardless of inoculation titer. Herpes simplex virus type 1 was recovered from the artificial tears up to 7 days. CONCLUSION: Unlike adenovirus, HSV-1 does not survive in preserved fluorescein and proparacaine multidose solutions; therefore, office transmission is highly unlikely.

Emerging fluoroquinolone resistance in bacterial keratitis: a 5-year review.

OBJECTIVE: To identify resistance patterns to the fluoroquinolones for patients with bacterial keratitis. DESIGN: Retrospective observational case series. PARTICIPANTS: All cases of bacterial keratitis presenting to the Charles T. Campbell Ophthalmic Microbiology Laboratory at the Eye and Ear Institute of Pittsburgh from January 1993 to December 1997 were reviewed. A total of 1053 ocular isolates from 825 cases of bacterial keratitis were identified. MAIN OUTCOME MEASURES: In vitro laboratory susceptibility testing of ocular isolates to ciprofloxacin and ofloxacin was determined by the Kirby-Bauer disk diffusion method and interpreted using the National Committee for Clinical Laboratory Standards serum standards. RESULTS: The number of cases of bacterial keratitis per year decreased from 284 in 1993 to 75 in 1997. The ratio of gram-positive to gram-negative organisms changed from 81.8%:18.2% in 1993 to 51.4%:48.6% in 1997 (chi-square, 66.00; degrees of freedom, 4; P < 0.000001). Resistance of Staphylococcus aureus to ciprofloxacin significantly increased annually from 5.8% in 1993 to 35.0% in 1997 (chi-square, 19.80; degrees of freedom, 4; P < 0.0001) and for ofloxacin from 4.7% to 35.0% over the same period (chi-square, 21.32; degrees of freedom, 4; P < 0.001). Streptococcus species and coagulase-negative Staphylococcus species showed significant resistance to both fluoroquinolones but no change in resistance over the study period. The gram-negative organisms showed good susceptibility to the fluoroquinolones. CONCLUSIONS: This in vitro study shows a significant increased resistance of S. aureus to the fluoroquinolones from 1993 to 1997. In addition, gaps in fluoroquinolone coverage for Streptococcus and coagulase-negative Staphylococcus species raise concern for the use of monotherapy in treating bacterial keratitis. Contrary to what might be expected, the distribution of gram-positive to gram-negative organisms has shifted, with a decrease in the number of gram-positive organisms identified, while the number of gram-negative isolates has remained stable.

Evaluation of the shell vial technique for detection of ocular adenovirus. Community Ophthalmologists of Pittsburgh, Pennsylvania.

PURPOSE: The shell vial technique is a cell culture method that uses centrifugation and immunofluorescence to decrease the time required for a positive test. The authors evaluated the shell vial technique as a diagnostic test to detect adenovirus in conjunctival specimens of patients with adenoviral conjunctivitis. DESIGN: Retrospective and prospective case series. PARTICIPANTS: Forty-six patients with adenoviral culture-positive ocular infection. METHODS: The minimum time of incubation (days) that was required for testing clinical isolates with the shell vial was determined with adenovirus serotypes 5 and 8. In a masked retrospective study, 25 true-positive (frozen clinical samples) and 25 true-negative specimens were tested for the presence of adenovirus using the shell vial technique. The 25 true-negative samples included herpes simplex virus, Chlamydia trachomatis, Haemophilus influenzae, Streptococcus pneumoniae, and Staphylococcus aureus. In a prospective study, 21 patients who later tested positive in cell culture for adenovirus were concurrently tested with shell vial. MAIN OUTCOME MEASURES: The time of incubation was determined in days, and the sensitivity, specificity, positive and negative predictive values, and the efficacy of the shell vial test were determined. RESULTS: The minimal time of incubation for testing ocular samples by shell vial was 3 days. In the retrospective study, the sensitivity, specificity, positive predictive value, negative predictive value, and efficacy were 92%, 100%, 100%, 93%, and 96%, respectively. Comparably (P = 0.99), in the prospective study the sensitivity, specificity, positive predictive value, negative predictive value, and efficacy were 95%, 100%, 100%, 96%, and 97%, respectively. The shell vial (93%, 43 of 46) was equivalent (P = 0.42) to cell culture (100%, 46 of 46) for detecting adenovirus, but a positive result was obtained in significantly less time (3 days versus 9.41 +/- 6.23 days) (P = 0.00001). CONCLUSIONS: The shell vial technique was found to be a definitive method for identifying adenovirus from ocular specimens. A clear benefit for the ophthalmologist is that the test can provide a faster positive result (3 days) compared with conventional cell culture, which can take 1 to 3 weeks for adenovirus isolation.

Comparative antiviral efficacies of cidofovir, trifluridine, and acyclovir in the HSV-1 rabbit keratitis model.

PURPOSE: To determine the relative antiviral inhibitory activity of topical 1% and 0.5% cidofovir, topical trifluridine (Viroptic; Burroughs-Wellcome, Research Triangle Park, NC), and topical acyclovir (Zovirax; The Wellcome Foundation, London, UK) during a 7-day period for the treatment of herpes simplex virus type 1 (HSV-1) keratitis and HSV-1 replication in the New Zealand rabbit ocular model. METHODS: In a series of four experiments using a two-eye design, a total of 80 New Zealand rabbits were inoculated in both eyes with HSV-1 McKrae after epithelial scarification. Forty-eight hours after inoculation, the rabbits were randomly assigned to a treatment group. Five treatment groups (16 rabbits/group) were evaluated: I, 1% cidofovir, twice daily for 7 days; II, 0.5% cidofovir, twice daily for 7 days; III, 3% acyclovir ointment, five times daily for 7 days; IV, 1% trifluridine, nine times daily for 3 days, then 4 times daily for 4 days; and V, control vehicle twice daily for 7 days. HSV-1 dendritic keratitis was graded in a masked fashion by slit-lamp examination on days 2, 3, 5, 7, 9, 11, and 14. Ocular viral cultures were obtained after slit-lamp examination on days 1, 3, 5, 7, 9, 11, and 14. RESULTS: Compared with the control group, all four treatment groups demonstrated significantly lower viral titers, fewer HSV-1-positive eyes/total during the treatment period, lower keratitis scores, fewer eyes with keratitis/total, and a shorter time to resolution of keratitis. Within the treatment groups, the 1% and 0.5% cidofovir treatments were significantly more effective than acyclovir and trifluridine as measured by the previous viral and keratitis parameters. CONCLUSIONS: Topical 1% and 0.5% cidofovir both appeared to be significantly more efficacious than topical trifluridine and acyclovir, during a 7-day course, in the treatment of experimental HSV-1 ocular disease in the New Zealand rabbit keratitis model.