The 213 households in the watershed (639 equivalent inhabitants) rely on on-site septic systems. Among them, 49 septic tanks (147 equivalent inhabitants) were located on a 500 to 600 m stretch of the stream. Untreated sewage of human origin (4 equivalent inhabitants) resulting from a dysfunctional septic Selleckchem MG-132 system was located 400 m from the sampling location corresponding to a input of E. coli which varies from 6.5 101 CFUs per 100 ml-1 in a wet period to 3.6 104 CFUs

per 100 ml-1 after a rainfall event. The land-use data were provided by the “”Groupement d’Intéret Public Seine Aval”", and data on beef and dairy cattle were provided by the “”Direction Départementale de l’Agriculture et de la Forêt (DDAF)”". Materials and sampling method Samples were collected

with autosamplers (ISCO 6700 s, Roucaire, Courtaboeuf, France) from the stream, near the swallow hole, during a wet period in February 2007 (high flow) and during a dry period in May 2007 (low flow), after a storm during a dry period in July 2007 (Table 1), and after a storm during a wet period in March 2008, with samples taken 5 h before the storm, 6 h after the storm, and 19 h after the storm (Figure 2). The site was equipped with dataprobes (YSI 6820) to measure turbidity. Suspended sediment concentration was measured by filtration through pre-weighed Millipore filters (0.45 μm). ICG-001 supplier Water (1 L) was collected by autosamplers every hour for 24 h, 250 ml of each flask were mixed until subsequent microbial analysis, except for the sampling campaign in March 2008. All samples were kept at 4°C until the microbiological analyses were carried out,

which occurred within 8 h. Enumeration of culturable Fenbendazole E. coli E. coli were enumerated using membrane filtration methods (0.45 μm HA047 Millipore, Bedford, MA, USA). E. coli were isolated from the water samples with a selective chromogenic media specific for E. coli, with the addition of a selective supplement for water samples (RAPID’E.coli 2 Medium and Supplement; Biorad, USA), and incubated for 24 h at 44°C. The threshold value for the enumeration of E. coli in water was 5 CFUs per 100 ml-1. E. coli isolates Two hundred and thirteen isolates of E. coli were isolated from the creek water. The isolates were taken from the membrane of RAPID’E.coli 2 medium and isolated on RAPID’E.coli 2 medium for 24 h at 37°C. Each clone of E. coli was stored on a cryo-bead system (AES laboratory, France) at -80°C. Four sets of isolates were obtained from the stream under different hydrological conditions: 44 isolates during dry season conditions (February 2007); 45 isolates during wet season conditions (May 2007); 34 isolates after a storm during the dry period (July 2007); and 90 isolates from the storm during the wet period (March 2008). Determination of the E.