Background and Objective:
Although several protocols have been developed to extract DNA for the diagnostic of soil-transmitted helminths (STHs), amplifying these extracts remains a challenge due to DNA polymerase inhibitors. This study aimed to determine stool mass, the type of DNA polymerase and assess a DNA extraction method for efficient molecular detection of STHs.

Methods:
Stool samples were collected from school-aged children and Kato-Katz enabled to search for STH infections. DNA was extracted from 10, 20, 40 and 80 mg of stool using cetyltrimethylammonium bromide (CTAB)-based method. The amount of stool for STH diagnostic was determined by amplifying specific DNA fragments of Ascaris lumbricoides. Performance of three DNA polymerases as well as CTAB-based method were assessed by amplifying specific fragments of different STH species. The cost linked to each DNA extraction was estimated.

Results:
DNA extracts from 97.9% of stools harbouring STH eggs revealed the presence of at least one STH species. The number of amplified DNA extracts from 10 and 20mg of stool was significantly higher than those of 40 and 80 mg. The “Q5 high fidelity DNA polymerase”, the “One taq DNA polymerase” and “Standard DNA polymerase” amplified respectively 97.9%, 54.6% and 34.8% of infected stools. Whatever the STH species, the “Q5 high fidelity DNA polymerase” amplified significantly more stool samples than other polymerases. Single PCR confirmed co-infections of A. lumbricoides with either T. trichiura or Necator americanus. Amongst hookworm infections, 10 and 13 were respectively due to N. americanus and Ancylostoma duodenale. CTAB-based method ($1.45) appeared less expensive that commercial kit.

Conclusion:
The CTAB-based method appears cheap and reliable to extract from 10 or 20 mg of stool samples, the DNA from STHs’ eggs. Its combination with the “Q5 high fidelity DNA polymerase” highlighted its ability for the molecular detection of different STH species in stool samples.