Heat and chlorine resistance of a soil Acanthamoeba sp. cysts in water.

Abstract

The study established the inactivation kinetic parameters of an Acanthamoeba cyst isolate subjected to heating and chlorination. A strain of Acanthamoeba was isolated and purified from an area surrounding a pilot food plant. Mature cysts (14days) were subjected to heat inactivation studies at 71, 76, 81, 86 and 91°C; and chlorination at 100, 200, 300, 400 and 500ppm. The decimal reduction times (D-values) at 71, 76, 81, 86 and 91°C were 18·31, 9·26, 7·35, 4·52 and 1·81min respectively. The calculated thermal resistance constant (z-value) was 21·32°C (R2 =0·96-0·97). The D-value in 100, 200, 300, 400 and 500ppm chlorine-treated water were 47·17, 25·06, 24·51, 23·70 and 18·55min respectively. The chlorine resistance constant (z-value) was 1179ppm chlorine (R2 =0·65-0·74). Results demonstrated high resistance of the isolated Acanthamoeba cysts towards the common methods applied in ensuring food and food processing environment sanitation. The resistance parameters of the test organisms established in this study may be used in the establishment of Sanitation Standard Operating Procedures (SSOPs), which are often based on inactivation of bacteria. These SSOPs could render better protection to food and food processing environments.