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,
Enterococcihave 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
Cow Enterococcus ID™ service is designed around the principle that certain DNA sequences
contained within strains of the
Enterococcus genus are specific to cattle. These
Enterococci sequences
can be used as indicators of cattle
fecal contamination. 6 Strains of
Enterococcus hirae and
Enterococcus mundtii have been shown to be from cattle and other ruminant sources. The
Cow Enterococcus ID™ service targets the cattle gene biomarker in
Enterococcus hirae.
One of the advantages of the
Cow 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.
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 cattle gene biomarker from
Enterococcus hirae.
These banding patterns confirm or negate the presence of the
Enterococci cattle gene biomarker. As
such, the banding patterns provide a reliable indicator of cattle
fecal contamination. To strengthen the
validity of the results, the
Cow Enterococcus ID™ service should be combined with other DNA analytical
services such as the
Cow Bacteroidetes ID™ and
Cow Fecal Virus ID™ services.
