Abstract
Disinfection of water is important in the control of waterborne diseases. It is used to kill or inactivate microorganisms in a gradual process that involves a number of physical–chemical and biochemical processes. The effects of sub-lethal gamma irradiation on survival and resistant pattern of two indicator organisms used in assessing water quality: Enterococcus faecalis and Escherichia coli were investigated in this study. Plate count agar and disc diffusion methods were used to determine the load and antibiotics susceptibility pattern of the test organisms respectively before and after exposure to different doses of gamma irradiation in sachet water samples. Survival pattern of the two indicator organisms to gamma- ray showed a decline in the populations of the organisms with time compared to the controls (non-radiated). The effect of the irradiation on the E. coli was dose dependent, it initially responded to the effects of the irradiation in the first 4 days of exposure compared to the control. On exposure to 4 and 5 gy gamma rays a minimum population was reached on the 7th day. At p<0.05 the population of E. coli was significantly different from the control. The survival pattern of Ent. faecalis also followed a similar growth pattern. The application sub-lethal gamma irradiation did reduce the population of the isolates and also affect the antibiotic susceptibility of the isolates.
Highlights
Water disinfection reduces the incidence of water-borne infections and lowers the rate of morbidity and mortality among infants and immunocompromised individuals
Enterococci are not permitted in 100 mL and in 250 mL drinking water samples from tap and bottled water respectively (CEU 1998)
This work was aimed at evaluating the effects of gamma radiation on survival and antibiotic susceptibility pattern of two water indicator organisms: Enterococcus faecalis and Escherichia coli introduced into sachet water
Summary
Water disinfection reduces the incidence of water-borne infections and lowers the rate of morbidity and mortality among infants and immunocompromised individuals. Chlorine dioxide, ozone, and irradiations are common mainly used in the treatment of drinking and wastewater (Akelah 2013; Ambulkar 2015) These chemical and physical agents kill and/or inactivate microorganisms (Akelah 2013). The U.S Environmental Protection Agency (EPA) has approved enterococci in place of faecal coliform bacteria as the preferred indicator of faecal pollution and health risk in marine water (Mote et al 2012). Both E. coli and Ent. faecalis are released through faeces of warm-blooded animals, including human beings (Wheeler et al 2002)
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