Coliphages tests

Coliphages are a group of bacteriophages that infect and replicate within coliform bacteria. Male-specific coliphages infect only the E. coli bacteria that express certain physical appendages used during sexual conjugation (pili). Somatic coliphages adsorb directly to the E. coli cell wall. Both male-specific and somatic coliphages are used as surrogates to indicate the presence of fecal material and viral pathogens in water. Depending upon the data needs of the project, male-specific or somatic coliphage tests may be appropriate. Coliphages are detected using either a presence-absence assay (EPA method 1601) or an enumerative assay (EPA method 1602).

Coliphage Group Matrix Method Sample Volume Sample Matrix
Male-specific coliphages  EPA 1601 100 ml SW DW WW 
Somatic coliphages    EPA 1601 100 ml  SW DW WW 
Male-specific coliphages  EPA 1602  100 ml   SW DW WW
Somatic coliphages EPA 1602  100 ml  SW DW WW
Male-specific coliphages EPA 1601   10-100L*  SW DW WW
Somatic coliphages  EPA 1601 10-100L SW DW WW
Male-specific coliphages EPA 1602 10-100L SW DW WW 
Somatic coliphages    EPA 1602    10-100L SW DW WW 
Coliphage Group Method Sample Volume Sample Matrix
Male-specific & Somatic coliphages EPA 1601 10-100L SW DW WW   
Male-specific & Somatic coliphages EPA 1602 10-100L SW DW WW 
*:  including 5” positively charged capsule filter
Coliphage source tracking by oligoprobe hybridization

Coliphage source tracking by oligoprobe hybridization

When water samples are subjected to EPA method 1602, an overnight incubation allows viruses to infect the E. coli host cells and create lytic zones called ‘plaques’. Viruses recovered from these lytic zones are subjected to oligoprobe hybridization using four separate enzymatically labeled probes that will bind with the genetic material of coliphages present within the enriched sample. Binding signatures make it possible to classify virus isolates into one of four distinct coliphage groups. Coliphages that correspond to human feces are statistically associated with phage groups 2 and 3, whereas animal coliphages are associated with phage groups 1 and 4. Depending upon the data requirements of the project, up to 10 male-specific coliphage isolates from each water sample can be subjected to hybridization. Pricing reflects cost per genotyped isolate and assumes that isolates are available from a prior EPA method 1602 test.