Water Research 39 (2005) 1621–1627 Enumeration of bifidobacterial populations with selective media to determine the source of waterborne fecal pollution Xavier Bonjoch à , Elisenda Balleste´, Anicet R. Blanch Departament de Microbiologia, Facultat de Biologia, Universitat de Barcelona, Avinguda Diagonal 645, E-08028 Barcelona, Spain Received 16 March 2004; received in revised form 19 January 2005; accepted 25 January 2005 Available online 14 March 2005 Abstract Bifidobacteria are one of the main groups of bacteria found in the intestine of humans and other animals. They have been proposed as indicators to identify the source of fecal pollution, since certain Bifidobacterium spp. are found only in humans. However, species identification remains difficult, and has limited their practical application. In this study, a simple assay based on the ratio of sorbitol-fermenting bifidobacteria to total colony forming units on Human Bifido Sorbitol Agar (HBSA) medium was developed. Ratios greater than 0.2 were indicative of human fecal pollution while animal-derived slaughterhouse effluent had a ratio less than 0.05. This is a low-cost, easily implemented approach which may have wide applicability when characterizing recent and high concentrated fecal pollution. r 2005 Elsevier Ltd. All rights reserved. Keywords: Bifidobacteria; Selective media; Fecal pollution 1. Introduction Maintenance of the microbiological quality and safety of water systems used for drinking, recreation and harvesting seafood is imperative. Pollution of these systems poses a threat to human health and, in addition, could lead to significant economic losses due to the closure of drinking water supplies, beaches and shellfish- harvesting areas. Water polluted with human feces is generally regarded as a serious risk to human health, perhaps greater than the risk associated with animal feces (Jagals and Grabow, 1996; Scott et al., 2002; Sinton et al., 1998) although there are outbreaks caused for animals (Hrudey et al., 2003). Consequently, identifying the origin of fecal pollution is paramount in assessing associated health risks and remedial actions. Identifying the origin of fecal pollution and discriminat- ing between human and animal sources is also important to protect water supplies, carry out epidemiological studies and to assign responsibility for environmental contamination (Jagals and Grabow, 1996; Puig, 1998). There is some controversy as to the ideal indicator microorganism to identify the sources of fecal pollution, both in food and water, because the traditional microorganism indicators only show the existence but not the source of the fecal pollution (Gilpin et al., 2003; Sinton et al., 1998). The genus Bifidobacterium is a candidate, since it is abundant in the intestinal micro- biota of humans and other warm-blooded animals (Mitsuoka, 1990). These organisms could be used to distinguish between human and animal pollution (Mara and Oragui, 1983; Nebra et al., 2003). They are found at a concentration of between 10 9 and 10 10 cells/g in feces (Tannock, 1997). Additionally, their anaerobic physiol- ogy, complex nutritional requirements and inability to multiply below 30 1C mean that they are unlikely to ARTICLE IN PRESS www.elsevier.com/locate/watres 0043-1354/$-see front matter r 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.watres.2005.01.018 à Corresponding author. Tel.: +34934021489; fax: +34934110592. E-mail address: xbonjoch@ub.edu (X. Bonjoch).