Microbiological Quality of the Water used in Agriculture in Sardinia

The microbiological quality of the water used in irrigation is crucial for the safety of products, such as fruit and vegetables, especially when destined to be consumed raw. However, the microbiological quality of this water is not defined at a community regulatory level or at a national level.

With our present work, we wanted to investigate the microbiological quality of the water used for crop irrigation in various Sardinian provinces. Since in most fields the irrigation water is filtered to remove any impurities, the sample was processed twice - both before and after the filtering process. Furthermore, with the purpose of hypothesising the potential health risks attributable to the consumption of crops from the tested fields, samples of horticultural product were collect. Any eventual seasonal differences in the values of microbial concentration were assessed. Microorganism faecal contamination indicators (Escherichia coli, total coliform and faecal streptococci), but even the presence of the opportunistic pathogen such as Pseudomonas aeruginosa were researched in irrigation water. Total mesophilic counts (TMC) were assessed at 36°C and 22°C. On horticultural products we researched both the indicators of process parameters, such as Escherichia coli, Total mesophilic counts at 30°C, Enterobacteriaceae, Total Psychrophilic counts and Pseudomonas aeruginosa, and pathogens, such as Salmonella spp, Listeria monocytogenes and Yersinia enterocolitica.

The number of target microorganisms, when present in irrigation water, was very limited: Escherichia coli, total coliform and faecal streptococci, were detected respectively in 48% and 67% of the water samples tested with average concentration values of 0.9, 1.2 and 1.4 log respectively. In fresh vegetable products, the total mesophilic counts (TMC) were found to have average values of 6.6x107 CFU/g. The average values of Enterobacteriaceae totalled 6.1x105 CFU/g; Escherichia coli was detected in only one sample (curly endive) with a value of 180 CFU/g.

The data highlights the high quality of the water and how this contributed to achieving satisfactory quality on prime material. However the use of filters, to eliminate impurities, and reservoirs, may represent a crucial issue, if not managed correctly.