Biology Reference
In-Depth Information
similarities to known viruses. 185 This approach allows novel and emerging
viral contaminants to be detected without bias toward any particular viral
group. However, little research involving environmental samples has yet been
completed using this technology. As of now, many environmental samples
show no significant nucleotide similarity to any sequences in the database. 186
8.3.4. Bacteria
More than 80% of diarrheal disease each year is attributed to drinking water
contaminated with waterborne pathogens. Currently, pathogenic bacteria in
water sources are the cause of the majority of waterborne disease outbreaks
in the United States. 187 Some of the most prevalent bacterial pathogens
belong to pathogenic strains of E. coli , Campylobacter spp., Heliobacter pylori ,
Klebsiella spp., Salmonella spp., Shigella spp., Legionella , Vibrio spp., and Yersinia
spp. 188 Routine monitoring of drinking and recreational water sources for
pathogenic bacteria is currently still based on the presence of fecal indica-
tor organisms (FIBs). 189 Specifically, microbiological quality is measured by
testing drinking water for E. coli , a bacterium that is always present in the
intestines of humans and animals and whose presence indicates the con-
tamination of the water source with fecal matter. The current guideline
indicates that for the water to be safe for consumption there should be no
E. coli detected per 100 mL.
The drawback of using FIBs is the lack of correlation with many water-
borne pathogens, including other bacterial contaminates. Moreover, the
lack of identification of the actual pathogen makes it hard to predict patho-
gens occurrence and public health risk. Therefore, many other methods
have been developed and are being tested for their usefulness in detect-
ing and tracking the actual pathogens in water sources. The ideal method
would identify the actual pathogen causing the outbreak, be specific
enough to resolve the organism down to a taxonomic significant level, be
sensitive enough to determine disease relevant levels, and be affordable for
standard routine use. Although many techniques have been tested, most
of the research to detect bacterial pathogens has concentrated on DNA-
based assays. They range from FISH to PCR, qPCR to RT-qPCR, and
microarrays to pyrosequencing and biosensor technology.
Regardless of the method employed, they all follow a common approach.
The sample to be tested usually needs to be processed in a way that ensures
the pathogen in question can be detected, which often requires a concen-
tration step for pathogens found at low infectious levels. Second, the nucleic
acid needs to be extracted. Third, the actual detection of the pathogen needs
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