Photoreactivation of Enterohemorrhagic E. Coli, Vre and P. Aeruginosa Following Uv Disinfection

Abstract

UV disinfection is noted to have some problems, one of which is photoreactivation. Photoreactivation allows inactivated microorganisms to regain viability following UV disinfection. The objective of this study is to determine the susceptibility of enterohemorrhagic Escherichia coli (EHEC) O26, vancomycin resistant Enterococcus (VRE), and Pseudomonas aeruginosa to UV radiation and photoreactivation. The conclusions obtained in this study can be summarized as follows. EHEC O26 exhibited apparent inactivation under sunlight after photoreactivation following UV inactivation. VRE exhibited apparent photoreactivation. The dose of UV light required for 90% inactivation of VRE with and without photoreactivation was 10.9 and 24.2 mW sec/cm 2 , respectively. P. aeruginosa exhibited apparent photoreactivation under fluorescent lamp and weak regrowth under dark conditions following UV inactivation. The dose of UV light required for 90% inactivation of P. aeruginosa with and without photoreactivation was 4.1 and 5.2 mW sec/cm 2 , respectively.

Assessment of the UV/Chlorine Process in the Disinfection of Pseudomonas aeruginosa: Efficiency and Mechanism

“…Both chlorination and ultraviolet irradiation are widely applied in water and wastewater disinfection. However, chlorination cannot effectively inactivate some chlorine-resistant bacteria, such as Pseudomonas, Sphingomonas, and Acinetobacter, , and UV disinfection is limited because photoreactivation and dark repair of bacteria can occur. − Moreover, both UV irradiation and chlorination can induce bacteria into a viable but nonculturable (VBNC) state, which is a potential microbiological hazard in drinking water systems. − The photolysis of chlorine generates various radicals (eqs –), such as hydroxyl radicals (HO • ) and reactive chlorine species (RCS), which can be effective for disinfection and can compensate for the limitations of UV treatment or chlorination alone . In addition, residual chlorine in the UV/chlorine treatment can provide residual protection in water distribution systems.…”

Photoinactivation of Staphylococcus aureus and Vibrio parahaemolyticus in the model aquatic microcosm: effect of light intensity and dissolved biodegradable organic compound

“…The reactivation observed seems inversely proportional to the light intensity applied. This photo-reactivation may be linked to three types of mechanisms (Harel et al 2004;Tosa et al 2009): the restoration of the damaged area (an enzymatic action restores the structure without breaking the skeleton), the removal of the damaged area (bases or group of incorrect nucleotides are replaced), and tolerance of the damaged area (there is no repair; the damage is accepted). In addition, Chrost & Faust (1999) suggested that, enhanced metabolism of bacteria grown in water samples that were previously exposed to radiation could also be due to photodegradation of dissolved organic matter and subsequent enrichment of water with easily utilizable substrates.…”