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ATP employing the bioluminescence reaction of firefly luciferin-luciferase-
ATP on a microfluidic chip. The method allowed reliable detection of
E. coli O157:H7 concentrations from 3.2 × 10 1 cfu µL −1 to 3.2 × 10 5 cfu µL −1
within 20 min. Heyduk and Heyduk 97 developed a FRET assay based on
two samples of the antibody, each labeled via nanometer-sized flexible link-
ers with short complementary oligonucleotides, when in too close prox-
imity, produce a fluorescent signal that can be detected. They found that
E. coli O157:H7 cells could be detected at levels of 300 cells in approxi-
mately 5 min. Although the method has been demonstrated as a proof of
concept, it has not been demonstrated using environmental water samples.
The limitations of the method are at the antibody recognition step and the
false detection of endogenous fluorescence in samples. The recent advances
in these biosensor platforms not only makes detection very rapid, but it also
promises to provide an early warning system for water quality.
Repeated detection of Salmonella has occurred from rivers, lakes, coastal
waters, groundwater as well as sewage and wastewater effluent. 199 The use
of FIBs to determine Salmonella contamination in water samples recently is
questionable. Wilkes et al. 10 suggested that a level of at least 89 cfu 100 mL −1
of E. coli was required for correlation with 89% of Salmonella -positive
samples. The use of Bacteroides 16S rRNA markers in river and wastewater
samples appeared to correlate positively with Salmonella , especially when
the concentration of human Bacteroides genetic markers was greater than
10 6 copies 100 mL −1 . 200 Although the infectious dose of Salmonella is quite
high, the emergence of multiple drug-resistant strains has generated con-
cern over the inability to track Salmonella reliably with the use of traditional
FIBs. With the introduction of molecular methods for pathogens detection,
the anaerobic Bacteroidales order have been suggested as an alternative bio-
logical indicator of fecal pollution according to their host-specific distribu-
tions, their short survival rate once released into the natural environment
and their abundance in feces from warm-blooded animals. 201 The consid-
erable advantage of these alternative indicators is their possible application
in determining the source of fecal contamination. Host-specific Bacteroida-
les 16S rRNA genetic markers were recently identified and PCR primers
have been designed for detection of human (HF183F-Bac708R), rumi-
nant (CF128F-Bac708R), and swine (PF163F-Bac708R) specific feces. 202
The markers were found to be useful to discriminate between agricultural
and human-related sources of contamination; however, their levels were
unable to be correlated to the presence of pathogens, such as Campylobacter ,
Salmonella , or E. coli O157:H7. 203
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