Inactivation of bacteria, virus and Cryptosporidium by a point-of-use device using pulsed broad spectrum white light

Pulsed light is a nonthermal processing technology recognized by the FDA for killing microorganisms on food surfaces, with cumulative fluences up to 12 J cm ؊2 . In this study, we investigated its efficacy for inactivating murine norovirus 1 (MNV-1) as a human norovirus surrogate in phosphate-buffered saline, hard water, mineral water, turbid water, and sewage treatment effluent and on food contact surfaces, including high-density polyethylene, polyvinyl chloride, and stainless steel, free or in an alginate matrix. The pulsed-light device emitted a broadband spectrum (200 to 1,000 nm) at a fluence of 0.67 J cm ؊2 per pulse, with 2% UV at 8 cm beneath the lamp. Reductions in viral infectivity exceeded 3 log 10 in less than 3 s (5 pulses; 3.45 J cm ؊2 ) in clear suspensions and on clean surfaces, even in the presence of alginate, and in 6 s (11 pulses; 7.60 J cm ؊2 ) on fouled surfaces except for stainless steel (2.6 log 10 ). The presence of protein or bentonite interfered with viral inactivation. Analysis of the morphology, the viral proteins, and the RNA integrity of treated MNV-1 allowed us to elucidate the mechanisms involved in the antiviral activity of pulsed light. Pulsed light appeared to disrupt MNV-1 structure and degrade viral protein and RNA. The results suggest that pulsed-light technology could provide an effective alternative means of inactivating noroviruses in wastewaters, in clear beverages, in drinking water, or on food-handling surfaces in the presence or absence of biofilms.H uman noroviruses are responsible for one-fifth of all cases of acute gastroenteritis worldwide (1). They spread directly via person-to-person contact (fecal-oral and vomitus-oral) or indirectly through food, water, and the environment (2). Natural biofilms in sewage treatment effluent could be responsible for many persistent waterborne outbreaks, since such biofilms have been found to harbor noroviruses (3, 4). Infection spreads quickly and widely, affecting individuals of all ages, especially where many people gather or live in close proximity, such as in long-term care residences, retirement homes, cruise ships, and the like. Infectious doses as low as 2,800 particles, the high viral loads in feces and vomit (up to 10 9 genomic copies per gram), persistence in the environment, prolonged duration of viral shedding even after symptoms have resolved, and inadequate long-term immunity all contribute to the high incidence of norovirus illness (5). Although the illness is usually mild and self-limiting, the large number of cases per year represents a considerable loss in productivity and constitutes a substantial burden on society (2, 6).Among the physical disinfection processes, pulsed-light treatment appears well suited for the disinfection of food contact surfaces in industrial and health care settings and for decontaminating water and beverages. It has been proposed as a means of nonthermal pasteurization for food preservation and for decontaminating air and packaging materials (7). It has proven effective for inactivati...

mentioning

confidence: 99%

Efficacy and Mechanisms of Murine Norovirus Inhibition by Pulsed-Light Technology

Vimont

Fliss

Jean

2015

“…The ability of UV light to inactivate microorganisms (in other words, the sensitivity of microorganisms to UV light) is known to differ from organism to organism (1,14,25). Many researchers have pointed out that parasites such as Cryptosporidium and Giardia, the most problematic waterborne pathogens, can be inactivated effectively by UV irradiation (1,2,5,6,7,15). This should be a great advantage of UV disinfection systems, because such parasites are known to be highly resistant to conventional chemical disinfectants, such as chlorine.…”

mentioning

confidence: 99%

Photoreactivation of Escherichia coli after Low- or Medium-Pressure UV Disinfection Determined by an Endonuclease Sensitive Site Assay

Oguma

Katayama

Ohgaki

2002

169

Photoreactivation of Escherichia coli after inactivation by a low-pressure (LP) UV lamp (254 nm), by a medium-pressure (MP) UV lamp (220 to 580 nm), or by a filtered medium-pressure (MPF) UV lamp (300 to 580 nm) was investigated. An endonuclease sensitive site (ESS) assay was used to determine the number of UV-induced pyrimidine dimers in the genomic DNA of E. coli, while a conventional cultivation assay was used to investigate the colony-forming ability (CFA) of E. coli. In photoreactivation experiments, more than 80% of the pyrimidine dimers induced by LP or MPF UV irradiation were repaired, while almost no repair of dimers was observed after MP UV exposure. The CFA ratios of E. coli recovered so that they were equivalent to 0.9-, 2.3-, and 1.7-log inactivation after 3-log inactivation by LP, MP, and MPF UV irradiation, respectively. Photorepair treatment of DNA in vitro suggested that among the MP UV emissions, wavelengths of 220 to 300 nm reduced the subsequent photorepair of ESS, possibly by causing a disorder in endogenous photolyase, an enzyme specific for photoreactivation. On the other hand, the MP UV irradiation at wavelengths between 300 and 580 nm was observed to play an important role in reducing the subsequent recovery of CFA by inducing damage other than damage to pyrimidine dimers. Therefore, it was found that inactivating light at a broad range of wavelengths effectively reduced subsequent photoreactivation, which could be an advantage that MP UV irradiation has over conventional LP UV irradiation.

“…Therefore, effective techniques for removing or disinfecting oocysts, other than chlorination, have been explored (23,27). Many researchers have reported that UV irradiation is an effective method to disinfect Cryptosporidium oocysts (1,6,8,16). However, the ability of Cryptosporidium to perform photoreactivation and dark repair has not been clarified yet in spite of the importance of these phenomena.…”

mentioning

confidence: 99%

“…However, these methods only determine their viability and do not address their ability to be infectious. The animal infectivity assay is said to be the gold standard for the determination of infection potential (16), but this method requires a number of animal hosts, is highly expensive, needs skillful technicians, and also involves a long testing time. Upton et al pointed out that cultured cells such as HCT-8 could be used as a host for Cryptosporidium instead of animal hosts (33), and many researchers have modified this cell culture method by combining it with other enzymatic or genetic techniques (11,24,30,36).…”

mentioning

confidence: 99%

“…Upton et al pointed out that cultured cells such as HCT-8 could be used as a host for Cryptosporidium instead of animal hosts (33), and many researchers have modified this cell culture method by combining it with other enzymatic or genetic techniques (11,24,30,36). Such cell culture methods have become attractive alternatives to the animal infectivity assay because they were reported to be equivalent to the animal method in determining the infectivity of Cryptosporidium parvum (16). On the other hand, it has also been reported that the methods based on reverse transcription-PCR detection of the specific mRNA in Cryptosporidium are effective to investigate their infectivity (20,25,31).…”

mentioning

confidence: 99%

See 1 more Smart Citation

Determination of Pyrimidine Dimers in Escherichia coli and Cryptosporidium parvum during UV Light Inactivation, Photoreactivation, and Dark Repair

Oguma¹,

Katayama²,

Mikami

et al. 2001

156

102

UV inactivation, photoreactivation, and dark repair of Escherichia coli and Cryptosporidium parvum were investigated with the endonuclease sensitive site (ESS) assay, which can determine UV-induced pyrimidine dimers in the genomic DNA of microorganisms. In a 99.9% inactivation of E. coli, high correlation was observed between the dose of UV irradiation and the number of pyrimidine dimers induced in the DNA of E. coli. The colony-forming ability of E. coli also correlated highly with the number of pyrimidine dimers in the DNA, indicating that the ESS assay is comparable to the method conventionally used to measure colony-forming ability. When E. coli were exposed to fluorescent light after a 99.9% inactivation by UV irradiation, UV-induced pyrimidine dimers in the DNA were continuously repaired and the colony-forming ability recovered gradually. When kept in darkness after the UV inactivation, however, E. coli showed neither repair of pyrimidine dimers nor recovery of colony-forming ability. When C. parvum were exposed to fluorescent light after UV inactivation, UV-induced pyrimidine dimers in the DNA were continuously repaired, while no recovery of animal infectivity was observed. When kept in darkness after UV inactivation, C. parvum also showed no recovery of infectivity in spite of the repair of pyrimidine dimers. It was suggested, therefore, that the infectivity of C. parvum would not recover either by photoreactivation or by dark repair even after the repair of pyrimidine dimers in the genomic DNA.