Our data replicate the finding  that male hand contamination rates differ between UK cities, with higher rates of contamination in northern than the southern cities studied. Men sampled in Liverpool were twice as likely to have bacteria of faecal-origin on their hands as males in Birmingham or London. In Newcastle, men were more than four times more likely to test positive than men from southern cities. It is unclear whether higher contamination risk also translates into high risk of infectious intestinal disease. Surveillance data comparing northern and southern regions in England tend to find higher rates in the south .
A number of variables besides location predicted hand contamination rates. Men who shook hands more often had a greater likelihood of contamination, presumably due to spreading contamination . Similarly, men who had engaged in soil contact (for example, through sporting activities or gardening) were more likely to be contaminated, most likely because of prior contamination of soil with animal or human wastes, or faecal bacteria that naturally also occur in the soil.
Lower hygiene scores - as measured by the items from the hygiene inventory  - were associated with greater likelihood of contamination. While previous research has demonstrated correlations between scores and actual hygiene behaviour in an experimental context , these data provide evidence that hand hygiene practices as measured by this scale are associated with levels of hand contamination, even though self-reported hygiene practices have been found unreliable as absolute figures [14, 15]. Psychometrically validated scales like that generated by Stevenson et al. are thus a promising tool for future research on hand hygiene behaviour.
The association between hand contamination and age, independent of other factors controlled for in the multivariate analysis, was unexpected. This effect may be due to increasing hygiene across the lifespan, or, alternatively, differences in lifestyle and behaviour not captured by the questionnaire.
These factors - age, hygiene, hand-contact, or soil contact - explain only a small part of the between-city trend in hand contamination rates. Possibly, we did not measure the existing variables with sufficient accuracy to exclude residual confounding. More likely, however, there could be other differences in hygiene, lifestyle and behaviour explaining the trend that our questionnaire did not cover. Possible explanations include differences in climate, type of occupation or leisure-time activities. It is possible that differences in normal skin flora rather than hygiene may resulted in longer survival rates of faecal contaminants, and thus higher contamination rates in northern cities. Whether the unexpected more frequent isolation of E. coli in Newcastle compared to other cities was due to chance or represents a true difference between the study sites could be the subject of future studies. In our previous study the differences in contamination between the sites were due to enterococcus as well as E. coli.
While bacteria like E. coli and Enterococcus faecalis are known to cause disease, the presence of some of the other identified bacteria on hands like Pantoea may not necessarily be a health hazard in itself. In any case, the presence of these bacteria appear to be indicative of a failure of good hygiene practice, and more specifically, of a failure to wash hands after contact with faecal material. Alternatively, these bacteria may have been picked up by touching a surface which someone with poor post-defecation hygiene had previously touched. The faecal indicator bacteria identified in this study may therefore be useful to study trends in the overall hygiene behaviour of a population. It is interesting to note that the overall contamination prevalence in this survey was markedly lower than in the previous study in all cities . The present survey was conducted in June and July 2009, coinciding with the first wave of the H1N1 influenza pandemic, and amid large scale public health campaigns emphasizing the role of hand hygiene for influenza control (the previous survey was done in August and September 2008). Increased handwashing and use of hand sanitisers may have contributed to the lower prevalence of faecal bacteria on hands, although other factors, such as temperature, cannot be excluded. Larger studies over a longer time scale are needed to confirm whether hand contamination is a useful surveillance tool for hand hygiene behaviour.
The study was conducted in the same sites as the previous study  in order to replicate the findings. Future studies could include different cities from the north and south of England to exclude the possibility that the observed trends may be due to specific characteristics of the included cities, independent of the geographic location.
This study did not attempt to quantify the number of bacteria that were found on hands; hence hands could be reported as positive with only one or very few bacteria. We also did not check for the presence of Pediococci or Aerococcus viridians, which may have been a source of false-positives for Enterococci. It should be noted that although the bacteria we isolated are likely to be of faecal origin, Enterobacter, Pantoea, and Klebsiella may have been picked up from non-faecal sources, e.g. from working with food or animals. However, as these were isolated in only a small number of our samples, the general pattern of our results are unlikely to be affected.
In conclusion, this study confirmed the higher prevalence of hand contamination in northern cities but failed to identify a reason for this trend. The study also confirmed that the contamination of hands with faecal bacteria is associated with typical risk behaviours for person-to-person transmission of pathogens (hand hygiene, shaking hands, soil contact, etc.). As unbiased estimates of risk behaviour, especially hand hygiene, can be difficult to obtain, microbiological methods could contribute to the study of hygiene behaviour .