Abstract The spread of antibiotic resistant bacteria (ARB) in environmental systems could lead to significant health concerns. A coastal aquifer in southern Italy (Villanova, Ostuni) was analyzed in this study in order to quantify groundwater pollution by ARB released in surface waters. During the time period September 2009 to July 2010, twenty-four samples were collected from surface and ground waters of the study area. Each sample was analyzed for microbiological/chemical quality and for ARB. Some strains of E. coli and Salmonella were tested for susceptibility to 17 antibiotics. Mathematical models were employed in order to simulate pathogens and ARB migration in groundwater. The experimental results suggested that surface waters were more contaminated than groundwater, whereas groundwater quality is highly variable depending on the sampling period as well as on the distance from the seacoast. EGU2011- HS8.1.7 GROUNDWATER POLLUTION BY ANTIBIOTIC-RESISTANT STRAINS RELEASED IN SURFACE WATERS Costantino Masciopinto (1), Rosanna La Mantia (1), and Constantinos Chrysikopoulos (2) (1) Water Research Institute IRSA-CNR, Bari, Italy (2) Environmental Engineering Laboratory, Department of Civil Engineering, Univ. of Patras, Greece Sampling wells Channel sampling locations ADRIATIC SEA Villages Ground elevation (m) Municipal treatment plant VILLANOVA S1 S2 S3 G1 G2 Study Area Methods 24 samples of surface water and groundwater were collected during four campaigns carried out in September 2009, February, May and July Groundwater were collected from 3 wells placed at 600, 1500 and 2800 m from the coast. Surface water samples were collected from 3 sampling points of an artificial channel that collects runoffs and effluents derived from a municipal treatment plant. Sampling points were at 5, 550 and 1000 m from the sea. Each sample was analyzed for microbiological/chemical quality and for ARB by the CLSI (Clinical and Laboratory Standards Institute, Pennsylvania, USA) manual method of diffusion in agar and, by using the automatic method Vitek 2 (BioMerieux, France). The susceptibility to 17 antibiotics has been then tested on some strains of E. coli and Salmonella. Models have been applied in order to simulate pathogens and ARB migration in groundwater. Preliminary Results Sampled surface water was more contaminated than ground water. Water quality is a function on the sampling date and distance from the sea coast. Salmonella was isolated at all sampling locations into the channel. Only during the 1st campaign (September 2009) was found in the groundwater, into the wells distant 600 m and 2800 m from the coast. Model simulations for bacteria transport are under developments. Of the 63 strains (i.e. isolates) of E. coli stained, 27% were resistant to one or more classes of antibiotics. 82 strains of Salmonella spp. and E. coli have shown percentages of antibiotic resistance ranging from 34% to 32%, respectively. 58% of 19 strains of Salmonella (3 S. typhimurium, 4 S. enterica subsp. arizonae, 12 Salmonella spp) were resistant to more than three classes of antibiotics. 2D Flow and Transport Models in 2D Fractures with Variable Apertures Flow: Colloid transport: Chemical oxygen demand in sampling sites at different distances from sea coast Map of the study area in southern Italy (Villanova, Ostuni) and locations of the six sampling sites Average water temperature, pH and electrical conductivity (EC) of sampled water Total bacterial count 37°C Sulphite-reducing clostridium spores AutumnWinterSpring CFU/100mL Mean of bacterial counts in surface and ground water over different seasons E. coli MPN/100mL C. perfringens AutumnWinterSpringSummer Enterococci AutumnWinterSpringSummer CFU/100mL Channel Wells CFU/100mL Summer Somatic coliphages PFU/ml Salmonella number of strains Salmonella (%) E. coli Distance from the sea (%) CFU/mL Average ARB in surface water (bars) and ground water (triangles and cross) samples at different distances from sea coast AUTOMATIC METHODMANUAL METHOD E. coli susceptibleIntermediate resistantFully resistant number of strains AUTOMATIC METHOD MANUAL METHOD Number of strains (i.e. isolates) in all samples at different categories of antibiotic resistance G3 500 m