Objective:

To evaluate the presence of shiga-like toxin (stx1 and stx2), intimin (eaeA), and haemolysin (hlyA) genes in E. coli isolates from private and public drinking water supplies in Upper Austria and to assess a possible public health risk. It is well known that consumption of food or potable water containing shiga-like toxin producing E. coli isolates can lead to haemorrhagic diarrhoea and even to haemolytic uremic syndrome. Outbreaks associated with public water supplies are well documented (Olsen et al. 2002; Bopp et al. 2003).

Methods:

Samples were taken from 255 private and public drinking water supplies in the western part of Upper Austria. This region is mainly supplied by wellwater and springwater. The samples were part of the routine surveillance programme according to the regulation concerning water intended for human use of the Austrian Health Authorities based upon the guideline 98/93 of the European Union. Of the 255 samples 102 were drawn from drilling wells, 86 from dug wells, 54 from springs and 13 from water supplies not otherwise specified.

The samples were taken according to standardised procedures. Hundred millilitres of each water sample was processed by membrane filtration. Endo-Agar was used to screen and isolation was performed on Chromogenic-Agar to yield colonies. Presence of E. coli genes was assessed by PCR according to published methods.

Results:

11 EaeA containing samples were found in all sorts of water supplies; the 3 HlyA positive E. coli were from one drilling well and two springs. Most importantly three shigatoxin 2-containing samples (one of which with additional stx1 gene) were discovered in one drilling well, one dug well and one spring.

Conclusion:

The evidence of shiga-like toxin (stx1 and stx2), intimin (eaeA), and hemolysin (hlyA) genes in E. coli isolates of 17 of 255 public and private water supplies in Upper Austria is not unexpected and underlines the importance of regular assessments. True EHEC strains, carrying both shigatoxin (stx1 or stx 2) and virulence genes (eaeA or hlyA), however, were not found. Efforts should be continued to guarantee the supply of the public and the private with potable water according to the guideline 98/93 of the European Union.

Literature:

Bopp, , et alJ Clin Microbiol 2003;41:174–180.

Olsen, , et alEmerg Inf Dis 2002;8:370–375.