Human Enterococcus ID^TM 

Determine quickly if your water source has human fecal contamination.

Important Note: The website and the services offered are for environmental professionals. This website is only a cursory overview of the services offered. Source Molecular is not responsible for errors or omissions on the web site. Furthermore, clients must understand the limitations of the services before submitting samples. Please call beforehand to discuss service details and type of samples to be submitted.

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^oC and 45^oC), 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.¹

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, particularly from human sources. 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 Human Enterococcus ID^TM service is designed around the principle that certain strains of the Enterococcus genus are specific to humans.^2,3,4 These Enterococci can be used as indicators of human fecal contamination. Strains of Enterococcus faecium, Enterococcus faecalis and yellow-pigmented Enterococci have been shown to be from human sources.^2,3,4 Within these Enterococcus spp. are genes associated with Enterococci that are specific to humans.⁵ The Human Enterococcus ID^TM service targets the esp human gene biomarker in Enterococcus faecium.^{6, 7}

One of the advantages of the Human Enterococcus ID^TM 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 human gene biomarker from Enterococcus faecium.

These banding patterns confirm or negate the presence of the Enterococci human gene biomarkers. As such, the banding patterns provide a reliable indicator of human fecal contamination. To strengthen the validity of the results, the Human Enterococcus ID^TM service should be combined with other DNA analytical services such as the Human Bacteroidetes ID^TM and Human Fecal Virus ID^TM services.

¹ Scott, Troy M., Rose, Joan B., Jenkins, Tracie M., Farrah, Samuel R., Lukasik, Jerzy  Microbial Source Tracking: Current Methodology and Future Directions. Appl. Environ. Microbiol. (2002) 68: 5796-5803.

² Wheeler, A.L., P.G. Hartel, D.G. Godfrey, J.L. Hill, and Segars W.I. 2002.  Potential of Enterococcus faecalis as a human fecal indicator for microbial source tracking.  J Environ Qual. 31(4):1286-93.

³ Bahirathan ML, Puente L, Seyfried P.   1998.  Use of yellow-pigmented enterococci as a specific indicator of human and nonhuman sources of faecal pollution.   Can J Microbiol 44:1066-1071.

⁴ Quednau, M., Ahrne, S., Molin, G.  Genomic Relationships between Enterococcus faecium Strains from Different Sources and with Different Antibiotic Resistance Profiles Evaluated by Restriction Endonuclease Analysis of Total Chromosomal DNA Using EcoRI and PvuII. Appl. Environ. Microbiol. 1999 65: 1777-1780.

⁵ Hammerum, A.M., and L.B. Jensen. 2002.  Prevalence of esp, encoding the enterococcal surface protein, in Enterococcus faecalis and Enterococcus faecium isolates from hospital patients, poultry, and pigs in Denmark.  J. Clin. Microbiol. 40: 4396.

⁶ Scott, T.M., T.M. Jenkins, J. Lukasik, and J.B. Rose. 2005. Potential Use of a Host Associated Molecular Marker in Enterococcus faecium as an Index of Human Fecal Pollution. Environ. Sci. Technol. 39: 283-287.