Effect of different fixatives on yield of DNA from human fecal samples

Abstract

Fixation and transportation of human fecal samples is often difficult in geographically remote locations due to unavailability of options for immediate freezing. In this study effectiveness of five different chemical fixatives were evaluated on human fecal samples including for supernatant using RNAprotect® Bacteria Reagent (Qiagen), 95% ethanol, acetone, TRIzol® and a mixture of all these fixatives, in addition to immediate freezing. DNA was extracted from the fecal samples using QIAamp® Fast DNA Stool Mini Kit as well as quality and yield of extracted DNA was monitored for a period of 30 days. It was found that except TRIzol®, all other preservatives showed good DNA quality and yield for a period of one month based on agarose gel electrophoresis, Nanodrop and Qubit fluorometric measurements. It was also found that supernatant of fecal sample fixed with RNAprotect Bacteria Reagent gave reliable DNA yield in comparison to other various fixatives. The study also revealed that quality and yield of DNA from fecal samples fixed in acetone were very promising since it is a cost-effective fixative. Overall, the study shows future applicability for downstream DNA analyses of the RNAprotect® Bacteria Reagent, 95% ethanol, acetone, and a mixture of all these fixatives for fixing human fecal samples to be collected from geographically remote locations or in regions where available resources are largely limited.