Acanthamoeba keratitis in New Zealand, including two cases with in vivo resistance to polyhexamethylene biguanide

Background: Acanthamoeba keratitis is an uncommon corneal infection that ca n run a protracted course with, at times, serious visual results, Eighty-fi ve per cent of cases occur in soft contact lens wearers. The first New Zeal and case occurred in 1990 and only seven cases have been identified in New Zealand to the end of 1996, Methods: We surveyed the ophthalmologists looking after these seven cases o f acanthamoeba keratitis as to time to diagnosis, treatment and outcome. Results: New Zealand has a low incidence of this disease. All cases were so ft contact lens wearers with defective care in every instance. After an ini tial two late-diagnosed cases, the time to diagnosis for four of the five o ther cases has been within 2 weeks, Medical treatment has varied over this series, but since the introduction of the cationic antiseptics polyhexameth ylene biguanide (PHMB) and chlorhexidine in 1992, the last live cases were all treated wi-th PHMB. One case diagnosed wi-thin 2 weeks ran a devastatin g course, despite intensive PHMB, and a second case remained culture positi ve after I year of PHMB and the late addition of chlorhexidine. Debridement , 0.1% PHMB and hexamidine eventually settled this eye. Conclusions: For treatment PHMB, hexamidine rather than propamidine and sur gical debridement are favoured. While ali Acanthamoeba isolates show good i n vitro sensitivity to PHMB, the in vivo response is not always proportiona te. A bacterial endosymbiont may have been a factor in the favourable outco me of one protracted case.