Bacteriophages as indicators of enteric viruses and public health risk in groundwaters.

Low concentrations of all types of bacteriophages in groundwater limit their power to predict the presence of enteric viruses. There is little concordance in the literature regarding phage detection methods, thus making comparisons extremely difficult. Different authors have used different hosts, phage concentration methods, and end-point determinations. Also, markedly different volumes of sample have been employed, varying from 1 litre to 400 l. Bacteriophage concentration methods are not reproducible. There has been marked variability among groups in the natural substrates used (for example, beef extract), the type of adsorbing filter used, centrifugation instruments and conditions, and the delivery of the concentrate to the host cells. There is no consensus on the best bacterial host strain. Currently, several are employed with each showing differential sensitivities and specificities. In particular, host stability must be considered. Host stability has two components: the ability of the host to continue to be receptive to the bacteriophage after continued sub-culture, and the lack of lysogenic or temperate bacteriophage in the host cell line which may be randomly and unpredictably activated. There is a lack of consistent recovery of bacteriophages from individual faecal specimens. In particular, only approximately 3% of individual humans carry the FRNA phages. While there is some evidence to indicate that the phages multiply in sewage, it is not clear how they do so since the host pili should not be produced at lower temperatures. These ecological factors need to be understood. Of all the phages thus far studied, Bacteroides fragilis HSP40 has the highest recovery rate from individual people. However, Bacteroides, being an anaerobe, is a difficult host for routine laboratory analysis. Methods for the enumeration of F(+)-specific phages and Bacteroides phages are complex, time-consuming, costly and not reproducible. Conversely, somatic coliphage methods are simpler and results can be available in 4-6 h. The occurrence of phages and viruses in groundwater depends on physicochemical characteristics that control their fate and transport in the groundwater/aquifer environment. There are very little actual data taken from the field that allow an understanding of the ecology and life span of phages in their natural environment. Moreover, the ability of phages to serve as a source of food for other microbes needs to be understood. There has been a lack of association of bacteriophage recovery with gastroenteritis outbreaks due to enteric viruses. There is only a small epidemiological database concerning the occurrence of enteric viruses in groundwater.

Enumeration by a miniaturized method of Escherichia coli, Streptococcus bovis and enterococci as indicators of the origin of faecal pollution of waters.

Counts of Escherichia coli, faecal streptococci and enterococci were made on faecal specimens from human and animal origin and urban raw sewage waters, with microtiter plates containing selective substances. Escherichia coli was more numerous than faecal streptococci and enterococci in 80% of the samples regardless of the origin. Consequently the use of the ratio E. coli/faecal streptococci to distinguish human from animal origin of faecal pollution is questionable. Enterococcus faecalis was predominant in human and poultry faeces, Streptococcus bovis was typical of the bovine faeces and to a lesser extent also of pig faeces whereas Enterococcus durans, Ent. hirae and Ent. faecium did not characterize any faecal source. Streptococcus bovis could be distinguished in the microtiter plate by its inability to reduce triphenyl tetrazolium chloride (TTC) in the medium.

[Thermoresistance of Legionella]. / Thermorésistance des Legionella.

Cells of Legionella suspended in water were heated for 15 to 60 min, at temperatures between 40 and 70 degrees C, and their survival determined over 9 log-cycles. The survival curves were identical for the 6 strains, and were non-logarithmic. Implications of the resistance plateau observed are discussed.

[On the coliform organisms and their count in water supply analysis (author's transl)]. / A propos des coliformes et de la colimétrie des eaux d'alimentation.

Many psychrotrophic coliform organisms are isolated from samples of water supply. They are coming from water or soil and not from animal faeces. It is therefore necessary to identify coliform organisms to interpret accurately the results of potability analysis.

Isolation of Naegleria fowleri from the cooling pond of an electric power plant in France.

Eleven strains of Naegleria have been isolated from 126 samples of the cooling pond of an electric power plant near Metz, France. Three strains showed specific characters of N. fowleri (pathogenicity for mice after intranasal instillation, immunofluorescence with anti N. fowleri serum and non-agglutination with ConA up to 1 mg/ml. Some particular characteristics were noted; the cysts showed a high number of pores and the pathogenicity was is lower using Swiss mice than using NMRI mice. The need for a standardization of methods for isolation and characterization are discussed as well as the occurrence of N. fowleri at the site.