Enterococci are a subgroup of Fecal Streptococci and are characterized by their ability to grow in 6.5% sodium chloride, at low and elevated temperatures (10°C and 45°C), and at elevated pH (9.5). These microorganisms have been used as indicators of
fecal pollution for many years and have been especially valuable in the marine environment and recreational waters as indicators of potential health risks and swimming-related gastroenteritis.
Enterococci are benign bacteria when they reside in their normal habitat such as the gastrointestinal tracts of human or animals. Outside of their normal habitat,
Enterococci are pathogenic causing urinary tract and wound infections, and life-threatening diseases such as bacteraemia, endocarditis, and meningitis.
Enterococci easily colonize open wounds and skin ulcers.
Compounding their pathogenesis,
Enterococci are also some of the most antibiotic resistant bacteria. Studies have shown that certain strains of
Enterococci are resistant to expensive and potent antibiotics such as vancomycin. This is particularly worrisome for the medical community since these antibiotics are given as a last resort to fight severe bacterial infections.
Several intrinsic features of the
Enterococcus genus allow it to survive for extended periods of time, leading to its extended survivability and diffusion. For example,
Enterococci have been shown to survive for 30 minutes at 60°C and persist in the presence of detergents. As such, the inherent ruggedness of
Enterococcus confers it a strong tolerance to many classes of antibiotics.
The
Deer (Elk) Enterococcus ID™ service is designed around the principle that certain strains of the
Enterococcus genus are specific to deers. These
Enterococci can be used as indicators of deer
fecal contamination. Strains of
Enterococcus faecium,
Enterococcus faecalis and
Enterococcus columbae have been shown to be from deer sources. Within these
Enterococcus spp. are genes associated with
Enterococci that are specific to deers. By a process of elimination, the
Deer (Elk) Enterococcus ID™ service targets the esp gene biomarker in
Enterococcus faecium and
Enterococcus faecalis to determine the presence of the deer biomarker.
One of the advantages of the
Deer (Elk) Enterococcus ID™ service is that the entire population of
Enterococci of the selected portion of the water sample is screened. As such, this method avoids the randomness effect of selecting isolates off a petri dish. This is a particular advantage for highly contaminated water systems with potential multiple sources of
fecal contamination.
Accuracy of the results is possible because the method uses PCR DNA technology. PCR allows quantities of DNA to be amplified into large number of small copies of DNA sequences. This is accomplished with small pieces of DNA called primers that are complementary and specific to the genomes to be detected.
Through a heating process called thermal cycling, the double stranded DNA is denatured and inserted with complementary primers to create exact copies of the DNA fragment desired. This process is repeated rapidly many times ensuring an exponential progression in the number of copied DNA. If the primers are successful in finding a site on the DNA fragment that is specific to the genome to be studied, then billions of copies of the DNA fragment will be available for detection by gel electrophoresis.
The gel electrophoresis apparatus uses an electrical field to distinguish different DNA fragments according to their molecular weights. Lighter DNA fragments will move farther along the gel than their heavier counterparts. At the end of the procedure different bands of accumulated DNA fragments will aggregate at different parts of the gel. It is this accumulation of DNA fragments that creates a band on the gel. Researchers use these bands to distinguish certain genomes such as the deer gene biomarker from
Enterococcus spp.
These banding patterns confirm or negate the presence of the
Enterococci deer gene biomarker. As such, the banding patterns provide a reliable indicator of deer
fecal contamination. To strengthen the validity of the results, the
Deer (Elk) Enterococcus ID™ service can be combined with the
E. coli ID™ service that uses ribotyping DNA fingerprinting technology. With the
E. coli ID™ service, the DNA fingerprints (i.e. banding patterns) of the
E. coli isolates are analyzed to determine their source.
