Biology Reference
In-Depth Information
current protocols for identifying pathogens in the water and water-related
samples.
All of the methods that have been designed and developed to date need
to be assessed before they can be accepted as a routine means of MST.
To be recognized as a new method of fecal source tracking, each step of
a new protocol needs to be verified and the overall test needs to meet
regulatory standards. Field and Samadpour
3
have identified six stages in the
testing of fecal source tracking methods: (1) proof of concept, (2) feasibil-
ity and biological likelihood the new method can detect likely sources, (3)
application of the test to novel samples, (4) comparison to other methods,
(5) testing with blind samples, and (6) verification that the test leads to
improvement of water quality.
3
The current culture based indicator tests
would be comparators in stages (4) and (5).
Culture-based methods to determine fecal sources have scored low at
identifying novel pathogens or blind samples and are limited by the abil-
ity of the pathogens to be isolated on media. Techniques such as antibiotic
resistance patterns, carbon utilization profiling, and phage typing meth-
ods are time consuming and often require prior knowledge of the sample
source. Other phenotypic methods such as FAME have passed the proof-
of-concept and feasibility stages but rely on libraries of information to
predict the contaminate; therefore, they lack the ability to identify isolates
from outside of the library.
3
Culture-independent methods are fast becoming the methods of choice
for identifying pathogen content in samples and possibly as a new standard
for MST. They rely on extraction of a genetic marker from a sample and
detection of host-specific marker genes. The greatest asset of these methods
is their direct detection of a pathogen attribute and their speed of deliv-
ery. They are able to detect unculturable isolates as long as some knowl-
edge of the genome of the suspected contaminate is known. Most of these
methods—PCR-based, microarray, and biosensors—have shown proof of
concept and feasibility as MST methods
3
; however, they are still lacking
from method testing in real-life applications. Adoption of one method will
require extensive testing from both a comparison point of view to current
methods and a guarantee that the method will supply a technique that has
ease of use and is financially feasible.
Enteric virus detection is among the promising library-independent,
culture-independent tool that can be used for MST due to their presence in
host feces and their host specificity.
14
Enteric viruses are frequently detected
in the environment and are easily differentiated based on sequence differences
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