Decreased waterborne pathogenic bacteria in an urban aquifer related to intense shallow geothermal exploitation.

The implications of intensive use of shallow geothermal energy resources in shallow urban aquifers are still not known for waterborne pathogens relevant to human health. Firstly, we hypothesized that waterborne enteric pathogens would be relatively increased in heated groundwater plumes. To prove this, microbiological sampling of 31 piezometers covering the domain of an urban groundwater body affected by microbiological contamination and energetically exploited by 70 groundwater heat pump systems was performed. Mean differences of pathogenic bacteria contents between impacted and non-impacted monitoring points were assessed with a two-tailed independent Student's t-test or Mann-Whitney U and correlation coefficients were also calculated. Surprisingly, the results obtained revealed a significant and generalized decrease in waterborne pathogen contents in thermally impacted piezometers compared to that of non-impacted piezometers. This decrease is hypothesized to be caused by a heat shock to bacteria within the heat exchangers. The statistically significant negative correlations obtained between waterborne pathogen counts and temperature could be explained by the spatial distribution of the bacteria, finding that bacteria start to recover with increasing distance from the injection point. Also, different behavior groups fitting exponential regression models were found for the bacteria species studied, justified by the different presence and influence of several aquifer parameters and major, minor and trace elements studied, as well as the coexistence with other bacteria species. The results obtained from this work reinforce the concept of shallow geothermal resources as a clean energy source, as they could also provide the basis to control the pathogenic bacteria contents in groundwater bodies.

Serotipos de Samonella entérica en productos alimenticios de Zaragoza, comparación con aislamientos clínicos / Salmonella enterica serotypes in Zaragoza foodstuffs, comparation with clinical isolates

Hemos estudiado la evolución de las serotipos de Salmonella enterica en las muestras de productos alimenticios analizados en el Instituto Municipal de Salud Pública de Zaragoza en los últimos 20 años y la hemos comparado con la evolución de los serotipos de Salmonella en coprocultivos de pacientes de un hospital general universitario (Hospital Lozano Blesa) de nuestra ciudad y con los datos publicados en muestras de alimentos de otras regiones españolas. Los serotipos más frecuentes en alimentos en Zaragoza son Typhimurium (30.42%) y Enteritidis (24.51%), con variaciones importantes según grupos de productos y comparables con los datos informados en muestras de alimentos en nuestro entorno. Los serotipos más frecuetes en alimentos de nuestra ciudad, son también los más frecuentes en las muestras clínicas aunque con importantes diferencias porcentuales

We have studied the evolution of Salmonella enterica serotypes in foodstuffs samples analyzed in the Municipal Institute of Public Health of Zaragoza during the las 20 years, and we have compared them with the evolution of the Salmonella serotypes in patients coprocultures ofa university general hospital (Hospital Lozano Blesa) of our city and with the published data about food samples in other Spain regions. Typhimurium (30,42%) and Enteritidis (24.51) are the most frequent serotypes in food samples in Zaragoza, with important variations according to foodstuffs and comparable with the data reported in other Spanish regions. The most frequent serotypes in food of our city, are also the most frequent ones in the clinical samples although with important percentage differences