Existing Methods of Waterborne Pathogen Detection - Waterborne Pathogens: Detection Methods and Applications - page 56

3.4.2. Bacteria
As described above, there are many problems with indicator bacteria testing.
First, there is the possibility to underestimate bacterial density, especially when
bacteria are physically injured or stressed. For instance, slow lactose-ferment-
ing or lactose-negative Enterobacteriaceae , including pathogenic Salmonella spp.
and Shigella spp., could be underestimated by standard coliform test, which
leads to false negative conclusions. Additionally, some microorganisms in the
environment are viable but are either difficult to culture or are nonculturable.
This section briefly introduces alternative methods to detect bacteria,
especially those looking at direct detection of different bacterial species.
Many waterborne pathogens, such as all Vibrio species, have to be identi-
fied beyond the species level to determine their pathogenic potential. 5,6
Molecular methods provide a good approach to determine species, though
viability is often challenging to obtain.
Application of the PCR-based methods detected the presence of
Salmonella spp., Shigella spp., Campylobacter spp. and different patho-
genic strains of E. coli . More details on molecular methods are given in
Chapter 8 ( Fig. 3.6 ).
Figure 3.6 Bacteria detection: schematic illustrating culture versus molecular meth-
ods. Source: Reproduced with permission from Ref. 36 , http://mtin.de/DNA/DNA2012/
abstract.html . (For color version of this figure, the reader is referred to the online
version of this topic.)