Microbiological culture
A rolling method over a Plate Count Agar+additives(Balis Laboratorium BV, Boven-Leeuwen, The Netherlands) was used to evaluate the bacterial contamination. The distal 8-10 cm of the FE and the tip were cultured. The FE was rolled over the agar plate until the entire circumference had touched the plate. Sterile tweezers were used to fix the FE, to prevent partial lifting of the FE from the plate. The cultures were incubated at 36°C for 72 hours. A more detailed protocol can be found in Appendix 1.