DISCUSSION & CONCLUSIONS
Our results show that two biofilm samples from two different sites in the Scottish water distribution network (1514C and 1264C) contain DNA whose sequence matched published H. pylori sequences with 100% and 93% identity respectively (Table 3; Appendices 1 & 2).
All appropriate precautions to prevent contamination were adhered to and appropriate experimental controls undertaken to ensure a high degree of confidence that the DNA sequences produced were present in the original biofilm samples. The soil DNA extraction kit was validated and shown to recover H. pyloriDNA from drinking water effectively (Figure 1). All positive and negative PCR controls performed as expected suggesting that the PCR assay was able to amplify H. pyloriDNA and that there was no evidence of contamination (Figures 1, 2 & 3). The PCR assay was validated using a range of organisms closely related to H. pylori to minimise the risk that DNA form an organism related to but not H. pylori was amplified and was found to amplify DNA from one (out of five) closely related Helicobacter spp. (Figure 3). The PCR was not validated against all described Helicobacter spp.
Sequence analysis remains the most robust method of identifying a bacterial species but not all Helicobacter spp. have been sequenced and it is known from molecular studies of complex ecosystems that only a small proportion of bacteria present can be cultured. It is therefore possible that the data obtained during these studies point to a Helicobacter sp. that has yet to be sequenced or the presence of an unculturable species similar to H. pylori in the biofilm.
However identification of a DNA sequence with 100% identity to a portion of the 16S r RNA gene of H. pylori indicated that H. pyloriDNA was most probably present in the biofilm samples taken from the Scottish drinking water supply. Further work is needed to ascertain both the extent of the presence of H. pylori and its public health significance.