Published Ahead of Print 21 March 2008. 10.1128/AEM.02415-07. 2008, 74(10):2997. DOI: Appl. Environ. Microbiol. Ubomba-Jaswa and K. G. McGuigan Arias-Quiroz, M. Iriarte-Pu��a, A. Mercado, E. M. Boyle, C. Sichel, P. Fern��ndez-Ib����ez, G. B. Conditions Disinfection under Real Sunlight Bactericidal Effect of Solar Water http://aem.asm.org/content/74/10/2997 Updated information and services can be found at: These include: REFERENCES http://aem.asm.org/content/74/10/2997#ref-list-1 at: This article cites 40 articles, 12 of which can be accessed free CONTENT ALERTS more�� articles cite this article), Receive: RSS Feeds, eTOCs, free email alerts (when new http://aem.asm.org/site/misc/reprints.xhtml Information about commercial reprint orders: http://journals.asm.org/site/subscriptions/ To subscribe to to another ASM Journal go to: on March 27, 2012 by MICHIGAN STATE UNIVERSITY http://aem.asm.org/ Downloaded from

APPLIED AND ENVIRONMENTAL MICROBIOLOGY, May 2008, p. 2997���3001 Vol. 74, No. 10 0099-2240/08/$08.00 0 doi:10.1128/AEM.02415-07 Copyright �� 2008, American Society for Microbiology. All Rights Reserved. Bactericidal Effect of Solar Water Disinfection under Real Sunlight Conditions M. Boyle,1 C. Sichel,2 P. Ferna ��ndez-Iba ��n ��ez, 2 G. B. Arias-Quiroz,3 M. Iriarte-Pun ��a,3 A. Mercado,3 E. Ubomba-Jaswa,1,2 and K. G. McGuigan1* Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, Dublin 2, Ireland1 Plataforma Solar de Almer����a-CIEMAT, Ctra. Sene��s Km. 4, 04200 Tabernas, Almer����a, Spain2 and Centro de Aguas y Saneamiento Ambiental, Facultad de Ciencias y Tecnolog����a, Universidad Mayor de San Simo��n, Cochabamba, Bolivia3 Received 26 October 2007/Accepted 13 March 2008 Batch solar disinfection (SODIS) inactivation kinetics are reported for suspensions in water of Campy- lobacter jejuni, Yersinia enterocolitica, enteropathogenic Escherichia coli, Staphylococcus epidermidis, and endo- spores of Bacillus subtilis, exposed to strong natural sunlight in Spain and Bolivia. The exposure time required for complete inactivation (at least 4-log-unit reduction and below the limit of detection, 17 CFU/ml) under conditions of strong natural sunlight (maximum global irradiance, 1,050 W m 2 10 W m 2) was as follows: C. jejuni, 20 min S. epidermidis, 45 min enteropathogenic E. coli, 90 min Y. enterocolitica, 150 min. Following incomplete inactivation of B. subtilis endospores after the first day, reexposure of these samples on the following day found that 4% (standard error, 3%) of the endospores remained viable after a cumulative exposure time of 16 h of strong natural sunlight. SODIS is shown to be effective against the vegetative cells of a number of emerging waterborne pathogens however, bacterial species which are spore forming may survive this inter- vention process. Batch-process solar disinfection (SODIS) involves storing microbially contaminated drinking water in transparent con- tainers such as plastic bags or plastic or glass bottles. These are placed in direct sunlight for periods of up to 8 h before con- sumption (9). Over the past 15 years there has been a steady increase in the number of species that have been tested for their sensitivity to SODIS. However, several important species remain un- tested. Among these are Campylobacter jejuni and Yersinia enterocolitica, both of which have been recently described as emerging diarrheal pathogens in the developing world (20, 42). The biocidal effect of sunlight is due to optical and thermal processes, and a strong synergistic effect occurs for water tem- peratures exceeding 45��C (15) and UV discharge tubes (18) validation of the inactivation kinetics of some of the previously tested pathogens using natural rather than simulated sunlight is warranted. The aims of this study were (i) to identify the limits of disinfection for SODIS of drinking water by examining inacti- vation kinetics using natural sunlight for a variety of bacterial species and (ii) to determine whether the previously untested waterborne diarrheal pathogens C. jejuni and Y. enterocolitica are susceptible to SODIS. Five bacterial species were examined in this study: entero- pathogenic Escherichia coli (EPEC), Y. enterocolitica, C. jejuni, Bacillus subtilis, and Staphylococcus epidermidis. EPEC, Y. enterocolitica, and C. jejuni are gastrointestinal pathogens which cause diarrhea and enteritis in humans. EPEC remains a major cause of infantile diarrhea world- wide, though particularly in developing countries (41). Out- breaks of EPEC-associated gastroenteritis most often affect infants, especially those who are bottle fed, suggesting that contaminated water is often used to rehydrate infant formulae in underdeveloped countries (27, 38). Y. enterocolitica is most commonly contracted following ingestion of food or water con- taminated with the bacterium (40). Research indicates that Y. enterocolitica is capable of surviving for several weeks in nat- ural river water (37). Campylobacters have been associated with a number of outbreaks from contaminated drinking water (3, 39). The rate of Campylobacter infections worldwide has been increasing and in certain reports exceeds the incidence of salmonellosis and shigellosis (12, 19). Campylobacters have been associated with a number of outbreaks from contami- nated drinking water (8). Unlike the other species studied in this research, neither B. subtilis nor S. epidermidis can be considered to be a waterborne pathogen. The inactivation studies of S. epidermidis reported here were required as part of a baseline comparison for an unrelated optical inactivation study of the prebiofilmic plank- tonic phase of this species and are included here solely for reasons of comparison and completeness. Endospores of B. subtilis exhibit a high degree of resistance to inactivation by various physical treatments including wet and dry heat, UV and gamma radiation, chemical oxidants, extreme desiccation, vacuum, and acceleration (28, 29). MATERIALS AND METHODS Test organisms. The bacterial species used were Campylobacter jejuni (NCTC 11168), Yersinia enterocolitica WA314 serotype O:8, S. epidermidis ATCC 35984 (RP62A), and non-verotoxin-producing Escherichia coli O157 (nontoxigenic eae- positive wild-type clinical isolate provided by the Irish Health Service Executive Public Health Laboratories, Cherry Orchard, Dublin, Ireland laboratory strain * Corresponding author. Mailing address: Department of Physiol- ogy and Medical Physics, Royal College of Surgeons in Ireland, St. Stephen���s Green, Dublin 2, Ireland. Phone: 353 1 4022207. Fax: 353 1 4022168. E-mail: kmcguigan@rcsi.ie. Published ahead of print on 21 March 2008. 2997 on March 27, 2012 by MICHIGAN STATE UNIVERSITY http://aem.asm.org/ Downloaded from