Effects of simulated solar disinfection of water on infectivity of Salmonella typhimurium

To determine whether cells of Salmonella typhimurium rendered nonculturable by simulated salar disinfection retain infectivity for mice. Bacteria susp ended in water were exposed to UVA irradiation for up to 8 h. Culturability , determined by colony forming unit and Most Probable Number counts, fell b y six log(10) units, while cellular activity determined by the Kogure cell elongation test was retained by approximately 5% of the cells present after 8 h. Intraperitoneal doses of nonculturable cells and active but noncultur able (ABNC) cells exceeding the LD50 Of the test organism and BALB/c mouse host, respectively by 4 and 3 orders of magnitude failed to produce detecta ble infections, Culturable cells that had been irradiated for 1.5 h were le ss infective (virulent) than their nonirradiated counterparts. Nonculturabl e and ABNC cells of Salm. typhimurium produced by UVA irradiation do not re tain infectivity for mice. Although ABNC cells could be produced by low cos t solar disinfection systems, they do not appear to pose a potential infect ion hazard.