Physical, Environmental And Chemical Effects on The Survival of Blastocystis SP. Cysts

Abstract

The survivability of Blastocystis spp. cysts in chlorine, salt water, pH and ultra violet light exposure, detergent and alcohol has yet to be elucidated and is important to assess the viability of Blastocystis sp. especially when subjected to the collection and detection protocols for this parasite. Physical parameters such as storage temperature (25-30°C) and duration (day 0, 3, 5, 7), environmental parameters such as salinity (0.00, 0.71, 0.90, 2.00, 3.5%), pH (3.60, 6.04, 6.80, 7.42, 9.07, 11.00), UVC light and chlorine (0.0, 0.2, 1.0, 3.0, 5.0 mg/L), and chemical parameters such as 7X cleaning solution (0.0, 2.5, 5.0, 10.0%) and Bactol™ alcohol gel (0.0, 0.2, 0.4, 0.6, 0.8%) were assessed. Results indicated a significant reduction was observed in the viability of Blastocystis sp. cysts from 100.0 % on day 0 to 41.6 % on day 7 at room temperature and 4°C in water samples. A sharp decrease in the percentage of viable Blastocystis sp. cysts was observed at 2 and 3.5 % of salinity, where only 15.2 ± 2.4 % and 16.0 ± 0.9 % of viable cysts were detected, respectively. The parasites survived alkaline pH with a significant decrease in viability (p<0.01) 72.5 ± 3.7 % (pH 7.42) to 52.3 ± 1.8 % (pH 9.07) and 43.7 ± 6.7 % (pH 11.00). A significant (p<0.05) decrease of viability in Blastocystis sp. cysts (from 64.0 ± 3.2 % to 43.7 ± 4.9 %) after exposure of UVC light for 24 hr. There was no significant difference observed when exposed to calcium hypochlorite. The percentage of viable cysts ranged from 45.9 to 54.4 % as compared to control (67.2 ± 3.2 %). Cleaning solution 7X affected the viability of Blastocystis sp. cysts significantly at p<0.01 as compared to control (64.9 ± 7.8 %). At 2.5, 5.0 and 10.0 %, only 12.8 ± 0.0 %, 13.9 ± 1.8 % and 5.6 ± 0.8 % of Blastocystis sp. cysts were still viable respectively. Blastocystis sp. cysts was significantly reduced from 67.2 ± 3.2 % to 59.7 ± 1.8 % (p<0.05), 41.6 ± 3.2 % (p<0.01), 39.5 ± 1.8 % (p<0.01) and 31.9 ± 3.1 % (p<0.001) after exposure to Bactol™ alcohol gel. In conclusion, this study implied that the cysts of Blastocystis sp. are resistant and robust. Therefore, the results must be considered when developing collection and detection protocols of Blastocystis sp. from water sources.