Conclusions - Waterborne Pathogens: Detection Methods and Applications - page 367

groundwater. Furthermore, many viruses are resistant to disinfection, particu-
larly norovirus, which has demonstrated resistance to chlorination, and adeno-
virus, which has remained viable even after UV treatment. Bacteria have sizes
on the order of a few micrometers, are often less infectious, with some notable
exceptions (e.g. Escherichia coli O157:H7 and Shigella ) and are more susceptible
to chlorine disinfection. Parasites are the largest of the waterborne pathogens
and comprise protozoa and helminths. With regard to helminth infections,
this has decreased significantly over recent years as the causative agents (e.g.
the host within the water environment) are easily removed by filtration. Pro-
tozoa however, remain a problem due to a low infectious dose, longevity in
the environment, and resistance to water treatment methods.
Existing methods of monitoring for waterborne pathogens mainly rely
upon detection of fecal indicators. This strategy assumes that fecal indica-
tors, showing that waters have been fecally contaminated, will therefore also
indicate the presence of any pathogens. The advantages of this approach are
that the tests are cheap and easy to perform. However, studies have indi-
cated poor correlation between the detection of indicators and presence of
microbial pathogens and there are also concerns that this approach does not
allow a valid identification of the pathogen.
The alternative to indicator monitoring is undertaking of tests to directly
identify particular pathogens. This is extremely challenging due to the low
concentrations of pathogens in large water volumes; the requirement to
detect a single organism in a 100 mL water sample has been compared to
the problem of finding a single coffee bean in 40,000 Olympic-sized swim-
ming pools. Furthermore, it is often necessary to determine the species
and viability/infectivity of a microorganism to determine the pathogenic
potential. Indeed, for some pathogens, identification beyond the species
level is required, e.g. Vibrio species.
Various methods of direct detection exist, including cell culture based
methods, immunological methods, microscopy, and nucleic acid amplifi-
cation approaches. Each has advantages and disadvantages and the most
suitable choice of monitoring approach is likely to depend upon why mon-
itoring is being undertaken. Monitoring plays several key roles in the design
and implementation of water safety plans and can be applied for surveillance
or for operational or investigative means. However, whatever the applica-
tion, improvements in methods for water quality monitoring are required
and have been the subject of much research in recent years.
Section 2 of the topic has covered developments in sample processing, a
key stage in any monitoring protocol. A variety of sampling and analytical