The disinfection efficacy of MeniCare soft multipurpose solution against Acanthamoeba and viruses using stand-alone biocidal and regimen testing.

PURPOSE: To assess the disinfection efficacy of MeniCare Soft contact lens multipurpose solution against Acanthamoeba and viruses in suspension and when inoculated on to contact lenses and subjected to rub-and-rinse or no-rub-and-rinse care regimes. METHODS: MeniCare Soft was challenged with Acanthamoeba spp trophozoites or cysts, herpes simplex virus (type 1), adenovirus (type 8), and poliovirus (type 2) and the log reduction in Acanthamoeba viability and viral infectivity determined over time. In addition, contact lenses were incubated with Acanthamoeba and viruses and the number of viable organisms determined after the lenses were processed using rub-and-rinse or no-rub-and-rinse care regimes followed by a 4 hr soaking time. RESULTS: MeniCare Soft showed >3 log reduction against Acanthamoeba spp trophozoites and cysts after 6 hr exposure. Approximately 1 log reduction was found against the 3 viruses after 4 hr exposure. No surviving Acanthamoeba trophozoites or cysts were recovered from any of the contact lens tested when MeniCare Soft was used in a rub-and-rinse or no-rub-and-rinse care regimes (>5.0 log reduction). Rub-and-rinse regimen resulted in a 4.5 to 5.0 log reduction in viruses compared with 3.7 to 5.2 log when no-rub-and-rinse was used. CONCLUSIONS: MeniCare Soft showed effective disinfection efficacy against Acanthamoeba trophozoites and cysts using solution and regimen assays. The viruses were more resistant to disinfection in solution but were removed effectively from contact lenses using a rub-and-rinse or no-rub-and-rinse care regimen.

Disinfection efficacy and encystment rate of soft contact lens multipurpose solutions against Acanthamoeba.

OBJECTIVES: To assess the ability of commercial and experimental soft contact lens multipurpose solutions (MPS) to promote Acanthamoeba trophozoite encystment and their biocidal efficacy against Acanthamoeba trophozoites and cysts. The effects on encystment and disinfection efficacy by the incorporation of propylene glycol (PG) in the formulation of MPS were also investigated. METHODS: Acanthamoeba trophozoites (Acanthamoeba castellanii ATCC 50730 and Acanthamoeba polyphaga CCAP 1501/3G) were inoculated into MeniCare Soft, MeniCare Soft (-PG), Epica Cold II, OptiFree Plus, and Rohto C cube Softone-Moist MPS, and the percentage of encystment induced by each solution was determined after 24 hr. In addition, Acanthamoeba trophozoites and cysts (A. castellanii ATCC 50730 and A. polyphaga CCAP 1501/3G and Ros) were also inoculated into each of the five MPS, and their log reduction determined after 0, 1, 4, 6, and 24 hr of incubation using stand-alone assays. RESULTS: Significantly higher encystment rates were found with Epica Cold II for A. polyphaga CCAP 1501/3G and Rohto C cube Softone-Moist for A. polyphaga and A. castellanii compared with the other MPS assessed (P<0.05). MeniCare Soft, MeniCare Soft (-PG), and Opti-Free Plus produced little or no encystment, with mean encystment values ranging from 0.0% to 2.0%. A significantly higher disinfection efficacy was found with MeniCare Soft, MeniCare Soft (-PG), and Epica Cold II compared with Opti-Free Plus and Rohto C cube Softone-Moist (P<0.05). CONCLUSIONS: Significant differences in encystment rate and disinfection efficacy between MPS were found. The presence of PG in the formulation of MeniCare Soft did not affect the disinfection efficacy or the encystment rate. The latter indicates that other factors play a role in the induction of Acanthamoeba encystment after inoculation into MPS.

A novel strategy for the identification of genomic islands by comparative analysis of the contents and contexts of tRNA sites in closely related bacteria.

We devised software tools to systematically investigate the contents and contexts of bacterial tRNA and tmRNA genes, which are known insertion hotspots for genomic islands (GIs). The strategy, based on MAUVE-facilitated multigenome comparisons, was used to examine 87 Escherichia coli MG1655 tRNA and tmRNA genes and their orthologues in E.coli EDL933, E.coli CFT073 and Shigella flexneri Sf301. Our approach identified 49 GIs occupying approximately 1.7 Mb that mapped to 18 tRNA genes, missing 2 but identifying a further 30 GIs as compared with Islander [Y. Mantri and K. P. Williams (2004), Nucleic Acids Res., 32, D55-D58]. All these GIs had many strain-specific CDS, anomalous GC contents and/or significant dinucleotide biases, consistent with foreign origins. Our analysis demonstrated marked conservation of sequences flanking both empty tRNA sites and tRNA-associated GIs across all four genomes. Remarkably, there were only 2 upstream and 5 downstream deletions adjacent to the 328 loci investigated. In silico PCR analysis based on conserved flanking regions was also used to interrogate hotspots in another eight completely or partially sequenced E.coli and Shigella genomes. The tools developed are ideal for the analysis of other bacterial species and will lead to in silico and experimental discovery of new genomic islands.

The efficacy of Acanthamoeba cyst kill and effects upon contact lenses of a novel ultraviolet lens disinfection system.

PURPOSE: To assess the efficacy of a novel ultraviolet (UV) lens device on the killing of Acanthamoeba cysts and the impact of efficacious doses of UV upon soft contact lens parameter and material characteristics. DESIGN: Prospective, in vitro, experimental study of a device. METHODS: A UV lens device was constructed and used to expose Acanthamoeba cysts to various levels of UV irradiation. Once an efficacious dose, as defined by a greater than 3 log reduction, was determined (130 mJ/cm(2)), 6 soft contact lens materials (etafilcon A, senofilcon A, galyfilcon A, lotrafilcon A, polymacon, and comfilcon A) were exposed to that dose for 30 cycles and tested for visual parameters, mechanical parameters, and cytotoxicity. RESULTS: The UV device produced an average log reduction of over 3.5 log of Acanthamoeba cysts when the lens and solution inside of the inset case was irradiated with 130 mJ per cm(2) of UV or greater. After 30 cycles of 130 mJ per cm(2) UV dose each, no gross changes were observed in mechanical properties or cytotoxicity tests in any soft contact lenses tested. In visual parameters, polymacon and lotrafilcon A exhibited a shift in sphere power and diameter, respectively. CONCLUSIONS: The novel UV lens device was able to provide a marked log reduction to Acanthamoeba cysts, one of the most resistant ocular disease-causing organisms found in lens cases, without a detrimental effect on many lens materials.

Antimicrobial efficacy of multi-purpose contact lens disinfectant solutions following evaporation.

PURPOSE: Non-compliance is a significant factor in contact lens related microbial keratitis and includes solution reuse and failure to recap the lens storage case resulting in evaporation effects. To address this, impact of partial evaporation on the antimicrobial efficacy of multipurpose contact lens care solutions was investigated. METHODS: Solutions were evaporated under a stream of air to 2× and 4× concentration and challenged with Fusarium solani (ATCC 36031), Candida albicans (ATCC 10231) and Acanthamoeba castellanii (ATCC 50370). The level of organism kill at 6h was compared to the non-evaporated product. RESULTS: ReNu with MoistureLoc(®) (RML) lost 90-100% of biocidal activity against C. albicans on evaporation, 75-99% for F. solani and 29-33% with A. castellanii at 2× or 4× concentration, respectively. OPTI-FREE(®) RepleniSH(®) lost 72-90% efficacy against C. albicans and F. solani, and 61% at 2× and 10% at 4× concentration with A. castellanii. ReNu(®) MultiPlus, AQuify(®) Multi-Purpose and Biotrue™ showed only loss in efficacy with C. albicans at 4× concentration giving 79%, 34.5% and 48% reduction, respectively. No loss in biocidal activity on evaporation was obtained with Complete(®) Revitalens for all organisms. CONCLUSION: Partial evaporation can affect biocidal efficacy of multi-purpose solutions and may have been a significant factor in an outbreak of Fusarium keratitis cases associated with RML. Evaporation results in increased binding of cationic disinfectants to counter-ions in the formulation, reducing ability to attach and rupture anionic microbial cell walls. Interaction may also occur between the biocidal ingredient and other components, such as surfactants, resulting in sequestration of activity through micelle formation.

Development of a rapid DNA extraction method and one-step nested PCR for the detection of Naegleria fowleri from the environment.

Naegleria fowleri is a small free-living amoebo-flagellate found in natural and manmade thermal aquatic habitats worldwide. The organism is pathogenic to man causing fatal primary amoebic meningoencephalitis (PAM). Infection typically results from bathing in contaminated water and is usually fatal. It is, therefore, important to identify sites containing N. fowleri in the interests of preventive public health microbiology. Culture of environmental material is the conventional method for the isolation of N. fowleri but requires several days incubation and subsequent biochemical or molecular tests to confirm identification. Here, a nested one-step PCR test, in conjunction with a direct DNA extraction from water or sediment material, was developed for the rapid and reliable detection of N. fowleri from the environment. Here, the assay detected N, fowleri in 18/109 river water samples associated with a nuclear power plant in South West France and 0/10 from a similar site in the UK. Although culture of samples yielded numerous thermophilic free-living amoebae, none were N. fowleri or other thermophilic Naegleria spp. The availability of a rapid, reliable and sensitive one-step nested PCR method for the direct detection of N. fowleri from the environment may aid ecological studies and enable intervention to prevent PAM cases.

A comparison of regimen methods for the removal and inactivation of bacteria, fungi and Acanthamoeba from two types of silicone hydrogel lenses.

PURPOSE: To compare the antimicrobial efficacy of commercial contact lens solutions when used according to the manufacturers' recommended regimens with two types of silicone hydrogel lenses. METHODS: Four multipurpose contact lens care solutions were examined, representing manufacturer recommended regimens of "rub & rinse", "no rub, rinse" or "no rub, no rinse". Test organisms were Pseudomonas aeruginosa, Serratia marcescens, Staphylococcus aureus, Fusarium solani, Candida albicans and Acanthamoeba castellanii (trophozoites and cysts). Organisms, in the presence of organic soil, were inoculated on to Acuvue Oasys or Air Optix lenses and subjected to the solution manufacturer's recommended regimen. The number of surviving organisms on the lenses and in the soak solution was enumerated in accordance with ISO 14729. RESULTS: ISO 14729 dictates that for a given organism the combined average number of surviving microbes from the lenses and disinfectant soaking solution must be