Add 30 ml of ice cold PBS to 3 g of faecal sample and mix by vortexing at high speed for 5 min, then keep on ice

Centrifuge sample at 5000 rpm for 10 min at 4°C and transfer the supernatant to a clean 50 ml centrifuge tube

Filter the supernatant through a 0.45 μm syringe filter

Add 10 % 10% w/v PEG-8000 in saline (0.5 M NaCl) to filtrate, mix by inverting and incubate at 4°C overnight

Centrifuge sample at 5000 rpm for 20 min at 4°C and discard the supernatant.

Re-suspend pellet in 200 μl PBS and transfer it to a 1.5ml Eppendorf tube

Add an equal volume of chloroform to the sample and mix gently before centrifuging it at 2500 rpm for 5 min at room temperature

Transfer the aqueous phase into a new and sterile 1.5 ml tube

Add 40 μl of 10 mM CaCl2 and 50 mM MgCl2 to the sample, as well as 10 U of DNase and 10 U of RNase A

Incubate samples at 37°C for 2 h and then place them in a heatblock at 70°C for 10 min

Store at 4°C