Acanthamoeba polyphaga strain age and method of cyst production influence the observed efficacy of therapeutic agents and contact lens disinfectants.

The effects of age in culture and the type of medium used for induction of Acanthamoeba polyphaga (Ros) cysts on susceptibilities to polyhexamethylene biguanide (PHMB; 3 micro g/ml), chlorhexidine digluconate (30 micro g/ml), myristamidopropyl dimethylamine (20 micro g/ml), H(2)O(2) (3%), and two multipurpose contact lens solutions (MPS-1 and MPS-2, based on 1 micro g of PHMB per ml) were examined. Strain Ros-02 was cryopreserved on isolation in 1991, while strain Ros-91 had been in continuous axenic culture. Significant differences in susceptibilities to the disinfectants were found depending on the medium used for cyst preparation and the age of the test strain, with Ros-02 generally being more resistant.

Persistently culture positive acanthamoeba keratitis: in vivo resistance and in vitro sensitivity.

Purpose: To characterize the risk factors, clinical course, treatment outcome and the association between in vivo resistance and in vitro sensitivity for subjects with persistently culture-positive Acanthamoeba keratitis.

Design: Retrospective noncomparative case series.

Participants: Eleven subjects with repeatedly positive cultures for Acanthamoeba treated between January 1990 and December 2000, were reviewed.

Enhanced killing of Acanthamoeba cysts with a plant peroxidase-hydrogen peroxide-halide antimicrobial system.

The activity of H(2)O(2) against the resistant cyst stage of the pathogenic free-living amoeba Acanthamoeba was enhanced by the addition of KI and either horseradish peroxidase or soybean peroxidase or, to a lesser degree, lactoperoxidase. This resulted in an increase in the cysticidal activity of 3% (wt/vol) H(2)O(2), and there was >3-log killing in 2 h, compared with the 6 h required for comparable results with the peroxide solution alone (P < 0.05).

Activity of the amidoamine myristamidopropyl dimethylamine against keratitis pathogens.

Objectives: Microbial keratitis accounts for up to 30% of blindness in some less developed societies. The development of a single broad-spectrum topical antimicrobial effective against bacteria, fungi and Acanthamoeba would have a major impact on reducing the morbidity and simplifying the treatment of microbial keratitis. To this end, the activity of the amidoamine myristamidopropyl dimethylamine (MAPD) was investigated against common causes of microbial keratitis.

Activities of therapeutic agents and myristamidopropyl dimethylamine against Acanthamoeba isolates.

The activities of therapeutic agents and myristamidopropyl dimethylamine (MAPD) against Acanthamoeba strains recalcitrant to medical therapy were studied. MAPD minimum cysticidal concentrations were 6.25 to 25 microg/ml; 10 to 30 microg/ml gave at least a 3-log cyst kill after 6 h, and 50 and 100 microg/ml gave at least a 3-log cyst kill within 2 and 1 h, respectively.