Effect of low concentrations of benzalkonium chloride on acanthamoebal survival and its potential impact on empirical therapy of infectious keratitis.

IMPORTANCE: The significant antiacanthamoebal effect of benzalkonium chloride, at or below concentrations used for preservation of common ophthalmic preparations, should be understood both when choosing empiric antibiotic therapy for infectious keratitis and when assessing the persistent rise in Acanthamoeba cases in the United States since 2003. OBJECTIVE: To characterize the antiacanthamoebal efficacy of low concentrations of benzalkonium chloride (BAK) for drug preservation and therapeutic effect against Acanthamoeba. DESIGN: Experimental study with a review of the literature. SETTING: Laboratory. EXPOSURES: A concentration of 10(4) trophozoites of 3 well-characterized clinical strains of Acanthamoeba were exposed at 0.5, 2.0, 3.5, 5.0, and 6.5 hours to BAK (0.001%, 0.002%, and 0.003%), moxifloxacin hydrochloride (0.5%), and moxifloxacin (0.5%) + BAK (0.001% and 0.003%) with hydrogen peroxide (3%) and amoeba saline controls. MAIN OUTCOMES AND MEASURES: Amoeba survival was calculated using the most probable number method recorded as log kill values. The relationship of BAK concentration and exposure time as well as the relative effect of BAK and moxifloxacin on acanthamoebal survival were analyzed. RESULTS: Amoebicidal activity of BAK is both time dependent and concentration dependent in pooled and strain-stratified analyses (P < .001). Moxifloxacin demonstrated no significant independent inhibitory effect or additive effect to BAK efficacy on acanthamoebal survival. The profound antiacanthamoebal effect of BAK, 0.003%, was similar to that of hydrogen peroxide for certain strains. CONCLUSIONS AND RELEVANCE: Low concentrations of BAK, previously demonstrated to concentrate and persist in ocular surface epithelium, exhibit significant antiacanthamoebal activity in vitro at or below concentrations found in commercially available ophthalmic anti-infectives. The unexplained persistence of the Acanthamoeba keratitis outbreak in the United States, clusters abroad, and clinical studies reporting resolution or modification of Acanthamoeba keratitis without specific antiacanthamoebal therapy suggests that other contributing factors should be considered, including changes in the formulations used for empirical therapy of presumed infectious keratitis occurring in the same period.

The effect of contact lens materials on disinfection activity of polyquaternium-1 and myristamidopropyl dimethylamine multipurpose solution against Staphylococcus aureus.

OBJECTIVES: This study examined the interaction of seven different lens materials with a multipurpose solution (MPS) containing the disinfectants polyquaternium-1 (0.001%) and myristamidopropyl dimethylamine (0.0005%). The objective of this study was to determine whether the different lens materials affect the concentration of a disinfectant in this commercially available MPS and the efficacy of the disinfectant against Staphylococcus aureus. METHODS: Silicone hydrogel lenses (galyfilcon A, senofilcon A, comfilcon A, enfilcon A, balafilcon A, and lotrafilcon B) and a conventional hydrogel lens (etafilcon A) were soaked in polypropylene lens cases filled with commercially available MPS containing 0.001% polyquaternium-1 and 0.0005% myristamidopropyl dimethylamine for 6, 12, 24, 72, and 168 hours. Empty lens cases were also filled with MPS. After each time point, solutions from cases containing the seven types of lenses and controls were assayed for activity against S. aureus according to International Standards Organization 14729 standard with modifications. Test solutions were analyzed for polyquaternium-1 and myristamidopropyl dimethylamine concentration at each time point. RESULTS: The concentration of polyquaternium-1 and myristamidopropyl dimethylamine remaining in the lens cases was reduced only slightly over time. Storage with the lenses did not adversely affect biocidal efficacy of the solution, and in some cases, it was significantly better (P=0.0029). CONCLUSION: The efficacy of this polyquaternium-1 and myristamidopropyl dimethylamine MPS to kill S. aureus was not adversely affected by the presence of lens materials soaking in the cases. Thus, current methods for performing solution antimicrobial testing should be reevaluated.

Strategies to optimize conditions for testing multipurpose contact lens solution efficacy against Acanthamoeba.

OBJECTIVES: To optimize the growth, culture, and life cycle conditions for testing multipurpose solutions (MPS) against Acanthamoebatrophozoites and cysts to better inform the development of an appropriate test protocol. METHODS: Two strains of Acanthamoeba castellanii were grown using 2 different methods, bacterized and axenic. Amoebae grown from both methods and from both strains were treated with 4 different MPS as trophozoites and cysts, which were generated using 4 encystment methods. Experiments were run in triplicate with controls. A 5-tube most probable number method was used to enumerate the survivors and to determine the log kills. Statistical analysis was performed using effect screening. RESULTS: There was a marked difference in effectiveness among solutions, which varied with growth conditions (P<0.0001) and encystment method. Growth medium affected survival. In addition, there was a significant difference in cyst survival, which was dependent on encystment method (P=0.0013). The strain used was less of a factor in trophozoite resistance to MPS. Cyst resistance to MPS varied depending on which strain was used, but it was not a significant factor. CONCLUSIONS: When designing a contact lens solution efficacy testing protocol for Acanthamoeba, care should be taken to control for variables that may distort results. An appropriate protocol should include growing Acanthamoeba bacterized and allowing them to encyst naturally. By choosing optimized testing conditions, a more realistic efficacy of contact lens solutions can be determined which will result in better and safer products on the market.

The effects of contact lens materials on a multipurpose contact lens solution disinfection activity against Staphylococcus aureus.

OBJECTIVES: To determine the effect of 8 different lens materials on polyhexamethylene biguanide (PHMB) concentration in multipurpose solution (MPS) levels over time and to determine the effect of lenses on lens solution microbial efficacy over time. METHODS: Silicone hydrogel lenses and conventional hydrogel lenses were soaked in polypropylene lens cases filled with contact lens MPS containing 1 ppm PHMB for 6, 12, 24, 72, and 168 hours. Cases filled with the same solution without lenses were controls. After each time period, solutions from cases with the 8 types of lenses and controls were assayed for activity against Staphylococcus aureus according to International Organization for Standardization-14729 with modifications. Solutions were analyzed for PHMB concentration at each time point. RESULTS: Some of the different lens materials significantly affected the PHMB concentration (P<0.0001) and the biocidal efficacy. Etafilcon A lenses significantly decreased PHMB levels after only 6 hours of lens soak time. The product lot of MPS used was also significant (P<0.0001). Enfilcon A, senofilcon A, and lotrafilcon B lenses did not significantly decrease PHMB levels. CONCLUSIONS: The efficacy of MPS was affected by some lens materials and PHMB concentration. Lens materials differ in their effect on PHMB concentration and the subsequent efficacy of the MPS. Over time, some lens materials can significantly reduce the PHMB concentration and the MPS's microbial activity against S. aureus.

Material properties that predict preservative uptake for silicone hydrogel contact lenses.

OBJECTIVES: To assess material properties that affect preservative uptake by silicone hydrogel lenses. METHODS: We evaluated the water content (using differential scanning calorimetry), effective pore size (using probe penetration), and preservative uptake (using high-performance liquid chromatography with spectrophotometric detection) of silicone and conventional hydrogel soft contact lenses. RESULTS: Lenses grouped similarly based on freezable water content as they did based on total water content. Evaluation of the effective pore size highlighted potential differences between the surface-treated and non-surface-treated materials. The water content of the lens materials and ionic charge are associated with the degree of preservative uptake. CONCLUSIONS: The current grouping system for testing contact lens-solution interactions separates all silicone hydrogels from conventional hydrogel contact lenses. However, not all silicone hydrogel lenses interact similarly with the same contact lens solution. Based upon the results of our research, we propose that the same material characteristics used to group conventional hydrogel lenses, water content and ionic charge, can also be used to predict uptake of hydrophilic preservatives for silicone hydrogel lenses. In addition, the hydrophobicity of silicone hydrogel contact lenses, although not investigated here, is a unique contact lens material property that should be evaluated for the uptake of relatively hydrophobic preservatives and tear components.

Impact of contact lens materials on multipurpose contact lens solution disinfection activity against Fusarium solani.

OBJECTIVE: To investigate the effects of eight different soft contact lenses on disinfection efficacy of a multipurpose solution (MPS) containing polyhexamethylene biguanide (PHMB) against Fusarium solani. METHODS: Six silicone hydrogel lenses (galyfilcon A, senofilcon A, comfilcon A, enfilcon A, balafilcon A, and lotrifilcon B) and two conventional hydrogel lenses (polymacon and etafilcon A) were placed in polypropylene lens cases filled with MPS containing 0.0001% PHMB and soaked for 6, 12, 24, 72, and 168 hours. After each interval, depleted MPS from lens cases were removed and assayed for activity against F. solani according to International Organization for Standardization (ISO) 14729 stand-alone procedure. A portion was aliquoted for chemical analysis. RESULTS: Soaking etafilcon A, balafilcon A, and polymacon lenses for 6 hours reduced the concentration of PHMB in MPS by more than half the stated labeled concentration, with concentrations below the limit of detection for etafilcon A-depleted and balafilcon A-depleted solutions after 12 and 72 hours of soaking, respectively. Except for comfilcon A-depleted solutions, all others failed to consistently obtain one log reduction of F. solani. The solutions soaked with etafilcon A, balafilcon A, and polymacon lenses for 24 hours or more lost all or almost all fungicidal activity against F. solani. CONCLUSIONS: Over time, the disinfectant uptake by some lenses can significantly reduce the PHMB concentration and the fungicidal activity of the MPS against F. solani. Current ISO methodology does not address the reduction in microbiocidal efficacy when lenses are soaked in MPS. The ISO committee should consider adding "soaking experiments" to quantify the effect that contact lens materials have on the performance of MPSs.

Successful treatment of chronic stromal acanthamoeba keratitis with oral voriconazole monotherapy.

PURPOSE: To describe the treatment of chronic stromal Acanthamoeba keratitis (AK) with oral voriconazole monotherapy. METHODS: All cases of chronic stromal AK recalcitrant to traditional therapy subsequently treated with systemic voriconazole seen at the University of Illinois Eye and Ear Infirmary between June 2003 and July 2009 were reviewed for clinical presentation, clinical course, and outcome. RESULTS: Three eyes of 2 patients were identified with culture-confirmed chronic stromal AK unresponsive to traditional antiacanthamoebal therapies, requiring topical corticosteroids to maintain corneal clarity. Oral voriconazole 200 mg twice daily achieved a rapid but transient reduction of inflammation and elimination of corticosteroid dependency but, in both patients, recrudesced approximately 6 weeks after its discontinuation. Subsequent repeated and/or extended use of oral voriconazole alone resulted in complete resolution ranging from 7 to 11 months off all medications with final best-corrected visual acuity ranging from 20/20 to 20/25. CONCLUSIONS: Recalcitrant chronic Acanthamoeba stromal keratitis was successfully treated with extended systemic voriconazole administration with good preservation of vision. The clinical resolution of chronic stromal keratitis in our 2 cases suggests that voriconazole may have a larger role in the treatment of AK.

Isolation, morphologic, serologic and molecular identification of Acanthamoeba T4 genotype from the liver of a Temminck's tragopan (Tragopan temminckii).

Members of the genus Acanthamoeba are usually free-living amoebae that are found in a variety of ecological niches including soil, fresh and brackish water, dust in the air, heating, ventilating, and air conditioning filters, swimming pools and hot tubs. Occasionally they are also known to cause central nervous system infections in humans and animals. We isolated into culture an amoeba from the liver of a Temminck's tragopan (horned pheasant) (Tragopan temminckii) that died of amoebic infection. We identified the infecting amoeba as Acanthamoeba sp. based on culture characteristics, cyst morphology and immunofluorescence assays. Additionally, we identified the amoeba as Acanthamoeba, genotype T4, by sequencing a diagnostic region of the nuclear small subunit ribosomal RNA gene.

Polymicrobial keratitis: Acanthamoeba and infectious crystalline keratopathy.

PURPOSE: To report the early presentation, cause, and successful medical management of combined Acanthamoeba keratitis (AK) and infectious crystalline keratopathy (ICK). DESIGN: Interventional case series. METHODS: Retrospective review of 111 AK patients diagnosed and managed at the University of Illinois Eye and Ear Infirmary between June 1, 2003 and November 30, 2008 for an additional diagnosis of infectious keratitis. RESULTS: Of 5 AK patients with microbiologic evidence of an additional bacterial keratitis during their active AK treatment, concomitant ICK developed in 3 patients. All patients were examined within 3 weeks of their AK diagnosis and were found to have characteristic signs and symptoms consistent with ICK. Bacterial culture results at the time of AK diagnosis were negative in 2 patients, but subsequent culture results were positive for Streptococcus oralis. Initial culture results demonstrated light growth of methicillin-sensitive Staphylococcus aureus in the remaining patient, who had received partial antibiotic treatment. Topical corticosteroids were used before diagnosis in 2 patients and were in use in only 1 patient after AK diagnosis. All infections resolved with medical therapy alone. One patient later required penetrating keratoplasty for visual rehabilitation. CONCLUSIONS: In patients with AK, ICK can develop early and without either the use of corticosteroids or a preexisting epithelial defect, inconsistent with previously suggested mechanisms and major risk factors for secondary infection. Combined AK and ICK may exhibit increased pathogenicity with the onset of severe, often new, pain and acceleration of localized tissue loss and resultant scarring. Although early recognition and aggressive medical treatment were successful in resolving the combined infections in our cases, Acanthamoeba coinfection, and perhaps endosymbiosis, should be considered in the evaluation and clinical management of AK, especially in those cases progressing atypically. Further research is needed to understand the precise mechanism of the introduction of coinfectious pathogens and their role in the pathogenicity of AK.

The relative value of confocal microscopy and superficial corneal scrapings in the diagnosis of Acanthamoeba keratitis.

PURPOSE: To compare the relative diagnostic value of confocal microscopy and superficial corneal cultures in the diagnosis of Acanthamoeba keratitis by using clinical and microbiologic definitions of disease. METHODS: Results of confocal microscopy, superficial corneal smear, and superficial corneal culture were analyzed for validity against 2 different microbiologic and a clinical composite standard for Acanthamoeba keratitis. RESULTS: In patients with both clinical characteristics and objective evidence of Acanthamoeba keratitis, confocal microscopy exhibited a sensitivity of 90.6% (95% confidence interval [CI]: 79.3%-96.9%) and a specificity of 100% (95% CI: 95.0%-100%). In patients with either positive culture or smear evidence of Acanthamoeba keratitis, confocal microscopy showed a sensitivity of 90.9% (95% CI: 78.3%-97.5%) and specificity of 90.1% (95% CI: 81.5%-95.6%). In strictly culture-positive patients, confocal microscopy showed a sensitivity of 92.9% (95% CI: 76.5%-99.1%) and a specificity of 77.3% (95% CI: 67.7%-85.2%). Of the 53 patients with Acanthamoeba keratitis, confocal microscopy was positive in 48 patients, whereas corneal smears and cultures were positive in 30 of 41 and 23 of 42 patients, respectively. Sensitivity of Acanthamoeba culture was 52.8% (95% CI: 38.6%-66.7%) in patients with a clinical diagnosis of Acanthamoeba keratitis. Simultaneous testing of smear and superficial corneal scraping resulted in a sensitivity of 83.0% (95% CI: 70.2%-91.9%), independent of the results of confocal microscopy. CONCLUSIONS: As confocal microscopy comes into wider clinical use, it remains in need of clinical and pathologic correlation. When performed and interpreted by an experienced operator, confocal microscopy is both sensitive and specific in the diagnosis of Acanthamoeba keratitis. Contemporaneous corneal scrapings are independently sensitive in the detection of Acanthamoeba keratitis, and a combination of both diagnostic modalities offers the highest likelihood of rapidly and accurately diagnosing Acanthamoeba keratitis in patients with atypical keratitis.

Prognostic factors affecting visual outcome in Acanthamoeba keratitis.

OBJECTIVE: To identify clinical and demographic factors associated with a worse visual outcome in Acanthamoeba keratitis (AK). DESIGN: Retrospective, case control study. PARTICIPANTS: A total of 72 eyes of 65 patients with AK who were diagnosed at the University of Illinois Eye and Ear Infirmary between May of 2003 and May of 2007 with treatment complete by October of 2007. The first affected eye was analyzed in bilateral disease. METHODS: Patient demographic, clinical characteristics, treatment methods, and final visual outcome data were collected through medical record reviews for all patients diagnosed with AK. Cases were defined as patients with AK with a visual outcome worse than 20/25 or those requiring penetrating keratoplasty (PKP). Controls were defined as patients with AK with a visual outcome of 20/25 or better. Logistic regression was used to estimate the odds ratio (OR) identifying prognostic factors associated with a worse visual outcome. MAIN OUTCOME MEASURES: Final visual outcome worse than 20/25. RESULTS: AK was confirmed through microbiologic evidence in 48 of 65 eyes (73.8%) or with confocal microscopy in 62 of 65 eyes (95.4%). Final visual acuity data were available in 61 of 65 eyes (93.8%); of these 61 eyes, 40 (65.6%) achieved a final visual acuity of 20/25 or better. In multivariable analysis, deep stromal involvement or the presence of a ring infiltrate at presentation was independently associated with worse visual outcomes (OR, 10.27; 95% confidence interval [CI], 2.91-36.17). Symptom duration before diagnosis was statistically predictive of disease stage at presentation (OR, 4.43; 95% CI, 0.99-19.83; multivariable analysis) but not final visual outcome (OR, 2.55; 95% CI, 0.83-7.88; univariate analysis). PKP was performed in 11 of 12 eyes with active disease. CONCLUSIONS: Corneal disease staging at presentation with slit-lamp examination was highly predictive of worse outcomes, allowing the identification of patients who might benefit from more aggressive medical or surgical intervention. Unlike in previous reports, patient-reported duration of symptoms before treatment was not reliable in predicting the final visual result in our series.

Efficacy of contact lens systems against recent clinical and tap water Acanthamoeba isolates.

PURPOSE: A recent increase in Acanthamoeba keratitis (AK) cases has been associated with Complete MoisturePlus, although many cases used other solutions. Complete MoisturePlus contains taurine and hydroxypropyl methylcellulose, unlike other multipurpose solutions (MPSs). The purpose of this study is to (1) determine contact lens solution efficacy against recent clinical and tap water Acanthamoeba isolates and (2) determine whether taurine inclusion increases Acanthamoeba survival against contact lens solutions. METHODS: Acanthamoeba T4 trophozoites from recent AK clinical and tap water isolates were placed on multiple concentrations of taurine-saline agar for 72 hours with Enterobacter aerogenes as prey. Amoebae were exposed for 6 and 24 hours to hydrogen peroxide solutions and MPSs (ReNu Multiplus, Complete MoisturePlus, AMO Trade Name, Opti-free Express, Clear Care, and UltraCare) and tested for survival. Plates were examined over the following week for growth. RESULTS: Strain type and solution affected survival. MPSs were ineffective, with 100% survival of all strains at 6-hour exposure. Hydrogen peroxide systems were more effective, with survival of 3/5 strains (Clear Care) and 1/5 strains (UltraCare) at 6 hours. The Chicago-area tap water strain was most resistant. Among hydrogen peroxide systems, no statistically significant difference in Acanthamoeba survival existed with taurine inclusion. CONCLUSIONS: Recent clinical and tap water Acanthamoeba strains, representing proven human pathogens and/or household strains, were highly virulent against contact lens solutions. The Chicago-area tap water strain was most resilient, a concern if tap water is contributing to the AK increase. Results further differentiated resistance among T4 strains, highlighting the importance of multiple strain testing.

The association of contact lens solution use and Acanthamoeba keratitis.

PURPOSE: To investigate Acanthamoeba keratitis (AK) risk factors. Diagnosis of AK, a rare but serious corneal infection, has recently increased significantly at the University of Illinois at Chicago (UIC) Cornea Service. DESIGN: Retrospective case-control study. METHODS: settings: University, tertiary care hospital. patients: Fifty-five AK cases with contact lens use were diagnosed between May 1, 2003 and September 15, 2006. Clinic-matched controls with contact lens use were recruited. Subjects completed surveys targeting lens hygiene, contact lens solution use, and water exposure. main outcome measure: Acanthamoeba keratitis. RESULTS: Thirty-nine (73.6%) cases and 113 (65.3%) controls participated; 38 cases had complete contact lens data. Thirty-five of 38 cases (92.1%) and 47 of 100 controls (47.0%) used soft lenses. Analysis was performed on 30 cases and 39 controls with matched pairs with soft lens use. Exclusive use of Advance Medical Optics (AMO) Complete MoisturePlus Multi-Purpose Solution was independently associated with AK in multivariable analysis (55.2% vs 10.5%; odds ratio [OR], 16.67; 95% confidence interval [CI] 2.11 to 162.63; P = .008). However, 38.8% of cases reported no use of AMO Complete MoisturePlus Multi-Purpose Solution either alone or in combination with other solutions. Although not statistically significant, additional hygiene-related variables (solution "reuse," lack of "rubbing," and showering with lenses) suggest a pattern of risk. CONCLUSIONS: AMO Complete MoisturePlus Multi-Purpose Solution use is independently associated with AK among soft contact lens users. However, it does not explain all cases, suggesting additional factors. Further research into environmental risk factors and hygiene practices is warranted, especially considering this is the second outbreak of an atypical, contact lens-related infection.