Microbiological characterization of freatobiont organisms: trial of an analytical protocol and hygienic implications

The objective of the present study lies in verifing the applicability of an analytical protocol to characterize the microbiology of the surface and gut of freatobiont organisms. The fundamental hypothesis of the study is that the subsurface microinvertebrates represent a protective condition for bacteria, whose presence in potable spring water is rigorously excluded by european standards of quality. The study was conducted between August 1996 and March 1998. Sediment samples were collected from the spring system of "Presciano", whose waters come from the regional aquifer of the Gran Sasso Massif in Italy (L'Aquila, Abruzzo). Drawings of samples were conducted at two different depths (-70 cm and -150 cm). The extration of the fauna (including copepodes) from sediments were achieved with the aid of a Wild M3 microscope. Isolate freatobiont organisms were placed in a sterile Petri plate and subjected to three washings. The liquids of the second and third washings were microbiological analyzed proceeding, in the course of the third washing, to squash the organisms with the aid of a sterile iron handle. Among the microinvertebrates, the copepod Harpacticoida Nitocrella pescei is the most represented species from the two levels of depth. In all, were isolated and identified 106 bacterial species; of these species only 12 (11.3%) did not show any adaptation to the temperature of 35 degrees C. The analytical protocol permitted to make evident a different distribution of microbial species between the two kinds of washing liquids, and this leads to considerate appropriate the adopted protocol. Even if the number of sediment samples analyzed was a few it was identified a great variety of microbial genera and species the greater part of which were mesophilic. This is a consequence of an adaptability that could be favoured by the presence of freatobiont fauna and that concern even microorganisms usually considered "faecal contamination indicators".