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Query: UMLS:C0022568 (keratitis)
 5,133 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Since the early 1960s, axenic culture and the development of procedures for the induction of encystation have made Acanthamoeba spp. superb experimental systems for studies of cell biology and differentiation. More recently, since their roles as human pathogens causing keratitis and encephalitis have become widely recognized, it has become urgent to understand the parameters that determine differentiation, as cysts are much more resistant to biocides than are the trophozoites. Viability of trophozoites of the soil amoeba Acanthamoeba castellanii (Neff), is conveniently measured by its ability to form plaques on a lawn of Escherichia coli. Use of confocal laser scanning microscopy with Calcofluor white, Congo Red or the anionic oxonol dye, DiBAC4(3) or flow cytometry with propidium iodide diacetate and fluorescein or oxonol provides more rapid assessment. For cysts, the plaque method is still the best, because dye exclusion does not necessarily indicate viability and therefore the plate count method has been used to study the sequence of development of biocide resistance during the differentiation process. After two hours, resistance to HCl was apparent. Polyhexamethylene biguanide, benzalkonium chloride, propamidine isethionate, pentamidine isethionate, dibromopropamine isethionate, and H2O2 and moist heat, all lost effectiveness at between 14 and 24 h after trophozoites were inoculated into encystation media. Chlorhexidine diacetate resistance was observed at between 24 and 36 h. The molecular biology and biochemistry of the modifications that underlie these changes are now being investigated.
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PMID:Encystation in Acanthamoeba castellanii: development of biocide resistance. 1124 85

An outbreak of Fusarium keratitis in contact lens users resulted in withdrawal of ReNu with MoistureLoc solution, although the exact cause of the outbreak remains enigmatic. We evaluated current and discontinued multipurpose cleaning solutions (MPSs; MoistureLoc, Equate, MultiPlus, and OptiFree Express) against plankton- and biofilm-derived cells of Fusarium oxysporum species complex (FOSC) and F. solani species complex (FSSC). The methods included a traditional assay based on CFU counts and a novel flow cytometry (FC) assay based on percent cell subpopulation (PCS) stained with two fluorochromes (Sytox Red and 5-chloromethylfluorescein diacetate). The tests were done with the respective manufacturers' recommended cleaning regimens (240 to 360 min) and under shorter exposures (15 to 60 min) to simulate inappropriate usage by the customers. FC assay measured PCS, which was available rapidly, in 5 to 7 h, whereas 24 to 48 h was needed for CFU counts, and there was good correlation between the two methods (r2=0.97). FC assays allowed identification of injured fungal cells, which are likely to be missed with growth assays. In general, a time- and inoculum-dependent survival pattern was seen for both FOSC and FSSC cells, and biofilm-derived cells were more resistant than plankton-derived cells. MultiPlus and Equate produced 100% sterilization of fungi even under shorter exposures. However, biofilm FOSC and FSSC cells survived for up to 4 h in MoistureLoc solution and up to 6 h in OptiFree Express solution under shorter exposure times. This finding was enigmatic, as OptiFree Express is not associated with any outbreak of Fusarium keratitis. This study provides additional support for possible roles that improper lens cleaning regimens and fungal biofilms could play as predisposing factors for Fusarium keratitis.
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PMID:Evaluations of shorter exposures of contact lens cleaning solutions against Fusarium oxysporum species complex and Fusarium solani species complex to simulate inappropriate usage. 2130 Aug 26