Reasons to perform PCR on fecal material may include:
(1) looking for enteric pathogens in a patient
(2) looking for enteric pathogens in animals
(3) looking for enteric pathogens in sewage or contaminated water supplies
(4) looking for colonic adenocarcinoma
Inhibitors to PCR in stool include:
(1) bile
(2) milk and/or meat proteins
(3) bacterial proteins or polysaccharides
(4) heme or hemoglobin (from gastrointestinal hemorrhage)
(5) high levels of urea
(6) presence of chelating agents such as humic acids from soil
(7) release of lactoferrin from neutrophils (in bacterial colitis)
(8) complex polysaccharides from vegetables in the diet
Features seen with an inhibitor:
(1) Results are negative or less than expected level for the target.
(2) There is failure of amplification for an internal control.
(3) Expected results are seen if inhibitors are avoided, removed or inactivated.
Inhibitors in blood can be removed or avoided in a number of ways:
(1) pretreatment over a silica membrane
(2) addition of bovine serum albumin (BSA)
(3) aqueous two-phase system (polyethylene glycol and dextran, Lantz et al)
(4) use of agarose blocks to embed DNA
(5) magnetic bead capture
plus many others
