Bacterial Indicators Of Faecal Contamination Research Articles

Bacteriological indicators of faecal contamination: result of a loading experiment with untreated urban wastewater.

Some observations were made on the behaviour of total coliforms, faecal coliforms, enterococci, numbers of aerobic bacteria, salmonellas and sulphur-reducing clostridia as bacterial indicators of faecal contamination of groundwater. A controlled irrigation experiment was carried out with untreated residual water in the alluvial aquifer of the Vega of Granada (Spain). The results obtained confirm the value of these parameters are useful indicators of very recent faecal contamination; and changes were detected as the level of the freatic layer increased and the chemical composition of the groundwater changed. These groups of micro-organisms persisted for about 200 h, with the exception of the aerobes which survived for much longer. Salmonellas were present at levels too low to calculate the extent of faecal contamination and sulphur-reducing clostridia were not detected. The results obtained show that irrigation with untreated wastewater offers a lower risk of microbiological contamination of groundwater compared with the direct addition of waters decanted and/or previously filtered.

Methods for Detecting Viruses in Foods: Background and General Principles

Viruses are sometimes transmitted through foods. Hepatitis A (HA) and some viral gastroenteritides are the diseases now known to be spread most frequently in this way, but any virus from the human intestines probably could be. Bacterial indicators of fecal contamination show limited correlation with the incidence of viruses in foods, so tests to detect the viruses themselves are needed. The epidemiologic record has led to selection of shellfish (bivalve molluscs) and vegetables and fruits as foods for which test methods should be described, and ground beef and raw milk are also considered here because of the great interest they have attracted among research workers. Viruses in foods are presently detected on the basis of the infections they cause in cultured primate cells, but these cell culture methods do not permit detection of the HA virus nor the most important of the foodborne gastroenteritis viruses. Current methods of virus detection entail liquefaction of the food sample, clarification of the sample suspension, possibly concentration of the clarified food extract, and inoculation of cell cultures; a certain amount of specialized equipment is required for some of these procedures. The inclusion of the proper controls is critical to interpretation of results that are obtained.

Viral pollution determination of superficial waters (river water and sea-water) from the urban area of Barcelona (Spain)

Various surface water systems in the metropolitan area of Barcelona (Spain), including two rivers and three beaches, were analysed for human viruses using glass powder as adsorbent to concentrate them. The method used allows concentration of large volumes (up to 2001), of water in a single step. Values obtained varied from 18.4 to values higher than 55 MPNCU 1 −1in the Besôs river and 0.44-44 MPNCU 1 −1in the Llobregat river. Viruses were isolated from approx. 70% of sea-water samples, the values ranging from 0 to 1.60 MPNCU 1 −1. Findings are discussed in terms of correlation between virus pollution and bacterial indicators of fecal contamination. Also, the suitability of glass powder adsorption to concentrate viruses in sea-water is discussed.