Risk of bacterial contamination after povidone-iodine disinfection for cataract surgery

BACKGROUND: Povidone-iodine alone or in combination with antibiotics is commonly used for presurgical disinfection in cataract surgery. In spite of the use of the combination Povidone-iodine and ofloxacin, the rate of ocular contamination as assessed from surgical knives was reported to be as high as 26 %. The aim of this study was to investigate the efficacy of diluted Povidone-iodine alone for surgical disinfection. PATIENTS AND METHODS: 126 consecutive patients undergoing elective cataract surgery with a conjunctival wound and a scleral tunnel received prior to surgery a disinfection with diluted Povidone-iodine eye drops (Braunol 1:10 diluted = 0.8 % Povidone-iodine, 3 times every 5 min). To assess residual bacteria on the ocular surface after disinfection, the surgical knives for the side ports and the scleral tunnel were cultured in thioglycolate broth. RESULTS: In 8 out of 126 (6 %) patients the culture from the surgical knives revealed a positive result (89 % coagulase negative Staphylococci). Four of these 8 cases occurred during a single list. All control cultures remained negative. CONCLUSION: Diluted Povidone-iodine eye drops alone are highly effective for bacterial disinfection when applied properly. The rate of contamination using 0.8 % Povidone-iodine in our series was considerably lower as compared to that of other studies.     

Acanthamoeba culbertsoni and contact lens disinfection systems

Acanthamoeba culbertsoni was used in this study inasmuch as its susceptibility to disinfection has not been examined. Although heat was found to be the most effective means of disinfection some cysts survived this procedure. Chlorhexidine exhibited a dose-response kill curve but the most effective concentrations are also corneo-toxic. Polyaminopropylbiguanide (0.00005%) has good effectiveness against the cyst but was not completely cidal at the dose tested. Thimerosal (0.002%) and hydrogen peroxide (3%) were found to be without effect. These findings should give contact lens practitioners guidelines for selecting a disinfection system for their patients.     

Comparative efficacy of contact lens disinfection solutions.

Using the D value method of analysis, we evaluated the relative antimicrobial effectiveness of eight contact lens disinfection solutions against a standard population of challenge organisms as defined in the Microbiological Guidelines proposed by the Food and Drug Administration (FDA). Six bacteria (Escherichia coli, Staphylococcus aureus, S. epidermidis, Streptococcus pneumoniae, Pseudomonas aeruginosa, and Serratia marcescens) and two fungi (Aspergillus fumigatus, Candida albicans) were investigated. The disinfectants included hydrogen peroxide (AOSept, MiraSept, Oxysept), chlorine-based solutions (Aerotab and Softab), soaking solutions containing synthetic, high molecular weight preservatives (ReNu and Opti-Free) and a thimerosal preserved soaking solution (Hydrocare Cleaning and Soaking Solution). The one-step hydrogen peroxide system (AOSept) was evaluated both with and without the catalytic disk. To facilitate comparison of the disinfecting solutions, we defined a new measure of performance, namely "power" of solution. This has an advantage over the "safety factor" because the solution power is independent of the size of the initial inoculum. Because different approaches to analysis may yield a wide range of D values for one set of survival data we call for adoption of a standardized approach. Our results suggest that one of the chlorine-based solutions fails to meet the FDA recommendations for bacterial challenge. Most solutions performed poorly against mycotic challenge. However, when used over longer disinfecting periods, 3% hydrogen peroxide and the Hydrocare solution gave adequate performance against fungi.     

A comparison of new hydrogen peroxide disinfection systems

A comparison of seven hydrogen peroxide systems for disinfection of contact lenses is presented. Each system differs by the manner in which the remaining peroxide is neutralized after disinfection. These differences are reflected in the total time required by each system, the resulting pH, unreacted peroxide and residual products. The flexibility and potential risks of each system are also discussed.     

Comparative efficacies of four soft contact lens disinfection solutions

We compared the antimicrobial activity of four soft contact lens disinfection solutions: Opti-One (Alcon), Opti-Free (Alcon), Complete (Allergan), and ReNu (Bausch & Lomb). Opti-One, Complete, and ReNu are multi-purpose solution systems which use a single solution for cleaning, rinsing, and disinfecting. Opti-Free is a rinsing and disinfecting solution designed to be used in conjunction with a daily cleaner. Each solution was tested on two different species of bacteria: Pseudomonas aeruginosa and Staphylococcus epidermidis. Inocula of 10⁸ colony-forming units per milliliter were tested in 9-ml aliquots of each test solution. Samples were taken at 10, 20, 40, 60, 120, and 240 minutes after inoculation, and the surviving bacteria were grown on plate media and enumerated after 48 hours. We found that Opti-Free and Opti-One were more effective than ReNu and Complete against S. epidermidis, and Complete was marginally more effective than the other three solutions against P. aeruginosa. None of the four multipurpose disinfection solutions tested was effective in completely eliminating P. aeruginosa by disinfection alone; therefore, it is important that contact lens wearers always clean and rinse their contact lenses before disinfection.     

Microbial contamination of contact lens care systems

We examined the contact lens care systems of 100 asymptomatic patients who used hard or soft contact lenses for correction of refractive errors for the presence of bacteria, fungi, Acanthamoeba, and endotoxin. Of 100 patients, 52 had contaminated contact lens care systems. Sixteen of 126 bottles (13%) of commercial contact lens care solutions were contaminated. Contaminated commercial solutions were opened and used for a longer period of time than uncontaminated solutions. Contamination was not found in bottles of preserved commercial solutions that were opened and used for less than 21 days. All 12 bottles of homemade saline were contaminated with bacteria, and Acanthamoeba was isolated from two of these bottles. Pseudomonas was found in the care systems of 12 patients. Bacillus species, which form spores resistant to heat, were found in the care systems of seven patients. Endotoxin, which is also resistant to heat, was detected in nine of 35 care systems (26%) tested. Potential pathogens were isolated from the conjunctiva of six patients.     

Effectivity of contact lens disinfection systems against Acanthamoeba culbertsoni

Thirteen commercially available contact lens solutions were tested for their ability to kill the cysts of Acanthamoeba culbertsoni. Miraflow, which contains 20% isopropyl alcohol, was the most effective at killing the cyst (94%), followed by solutions containing thimerosal (89%). The rigid gas permeable lens solutions in general were more effective than soft lens solutions. None of the solutions tested were completely cidal, but our data do suggest a combination of a good daily cleaner and disinfecting solution may be effective in reducing acanthamoeba exposure. These findings should provide guidelines for the practitioner in selecting the best disinfection system for the contact lens patient.     

Susceptibility of Acanthamoeba to soft contact lens disinfection systems

Members of the genus Acanthamoeba are increasingly recognized as agents of indolent, chronic, infectious keratitis. Recently, Acanthamoeba corneal infection has been reported in some persons who wear soft contact lenses. In this study, three "heat" and three "cold" soft contact lens disinfection systems were tested according to the manufacturers' instructions against Acanthamoeba castellanii and Acanthamoeba polyphaga in separate trials, and with appropriate controls. Suspensions of Acanthamoeba cysts or trophozoites of each species were tested individually. Each of the three heat disinfection units killed all acanthamoebae in one cycle in all trials. A chlorhexidine 0.005%/thimerosal 0.001% solution killed A. castellanii trophozoites and cysts, but those of A. polyphaga survived. Trophozoites and cysts of both species survived an alkyl triethanol ammonium chloride 0.013%/thimerosal 0.002% solution and a hydrogen peroxide 3% preparation. Heat disinfection overall appears to be more effective in killing Acanthamoeba trophozoites and cysts as compared to cold disinfection methods.     

The pH of over-the-counter hydrogen peroxide in soft lens disinfection systems

We evaluated the pH of six hydrogen peroxide (H2O2) soft lens disinfection systems which had over-the-counter (OTC) H2O2 substituted for the manufacturer's recommended H2O2. Substitution of four brands of OTC H2O2 into the five two-step disinfection systems resulted in a pH after neutralization which ranged from 6.70 to 7.55 pH units. There was a small but statistically significant difference in the pH after neutralization when OTC H2O2 was substituted for the manufacturer's recommended H2O2. There was a significantly lower pH after neutralization when the same brands of OTC H2O2 were substituted for the manufacturer's recommended H2O2 in a one-step H2O2 disinfection system. The pH after neutralization for the manufacturer's recommended H2O2 was 6.50 pH units. The pH after neutralization for the OTC H2O2 ranged from 3.35 to 4.77 pH units. This range is below the ocular comfort range of 6.6 to 7.8 pH units. These findings, along with other possible differences between OTC H2O2 and the manufacturer's recommended H2O2, indicate that OTC H2O2 should never be substituted for the manufacturer's recommended H2O2 in any H2O2 soft lens disinfection system.     

pH and H2O2 concentration of hydrogen peroxide disinfection systems

Hydrogen peroxide disinfection has caused discomfort for some soft contact lens wearers even though the solution was neutralized properly. The discomfort could be due to the endpoint pH of the system used or the residual H2O2 concentration. Using a digital pH meter and H2O2 concentration detection strips, we measured the pH and H2O2 concentration of seven different hydrogen peroxide disinfection systems over their recommended disinfection and neutralization cycles to determine their time courses and endpoint values. The final pH of the seven systems varied from 6.15 to 7.74 pH units. All systems resulted in residual H2O2 concentrations below threshold values. These findings indicated that the final pH may be the cause of patient discomfort after hydrogen peroxide disinfection and neutralization.     

The efficacy of disinfection systems for in-office storage of hydrogel contact lenses

To evaluate several methods of in-office storage of diagnostic hydrogel lenses, bacterial contamination rates of stored lenses were studied. Worn diagnostic lenses were treated with either AO Sept (CIBA Vision Corp.) or ReNu (Bausch & Lomb) disinfection systems and compared with lenses treated with heat or stored in unpreserved saline. At 1 week and at 1, 2, and 3 months, stored lenses were cultured for microbial contamination. Lenses stored in AO Sept or ReNu had 5.5 and 7.0% overall contamination rates, respectively, which were greater than the rate for heat-treated lenses (χ² = 44.43, p < 0.00005) at all time intervals. The contamination rate increased between the 1- and 2-month storage intervals, and it is recommended that practitioners using AO Sept or ReNu redisinfect trial hydrogel contact lenses at least once a month.     

Wolfram syndrome. Three case reports

Wolfram syndrome is a rare disorder defined by the occurrence of diabete mellitus, diabete insipidus, optic atrophy and deafness; DIDMOAD is a commonly accepted acronym. We report 3 further cases: two girls and one boy. Their age ranged from 12 to 17 years. The diagnosis was based on the presence of juvenile diabete mellitus, bilateral optic atrophy, urologic signs, with urinary tract dilation; and deafness in two cases. The ophthalmic signs of Wolfram syndrome are progressive decrease in visual acuity, constriction of the peripheral visual field with or without central scotoma, color vision disturbances and bilateral optic disc atrophy. Diabetic retinopathy is a rare complication. The other clinical features are discussed so as to differentiate between Wolfram syndrome and other optic atrophies associated with diabete mellitus. We discuss of the pathogenic hypothesis including the mitochondrial dysfunction.     

Change in pH of two-step hydrogen peroxide disinfection systems available on the spanish market

The pH of disinfection and neutralized solutions of three two-step hydrogen peroxide systems available on the Spanish market was measured before and after each neutralization cycle over a 32-day period. The pH of the solutions was measured with a micropH 2002 Crison pH-meter. The pH values obtained ranged from 3.22 to 3.90 for the disinfection (H₂O₂) solutions and from 7.01 to 7.32 after neutralization. These values lie within the ocular comfort range but significantly differ from the tear pH.     

Acute keratitis and contamination of contact lens care systems with Bacillus cereus

Two patients, both contact lens wearers, were treated for acute keratitis in both eyes. Routine microbiologic tests done for all four eyes confirmed merely the presence of Staphylococcus epidermidis in the conjunctival flora; neither fungi nor any viruses were detected on the patients' corneas. However, the contact lens soaking solutions were contaminated with a large number of microorganisms, including above all--or solely--Bacillus cereus. Two of the contact lenses used were also colonized by fungi of the genus Rhodotorula, Cryptococcus albicans and Wangiella dermatidis. The acute inflammation was treated quickly and effectively in all cases by specific antimicrobial therapy. Bacterial contamination of lens care systems is well known as a potential cause of keratitis in contact lens wearers. Although the clinical importance of Bacillus cereus in ocular surface pathology is still unknown, the cases reported here indicate that this microorganism may be of pathological significance in lens care systems. The authors therefore recommend including the lens care systems in routine bacteriologic tests in all cases of corneal infection where the patient wears contact lenses.