Testing faecal microbiota transplants (FMT): impedance cytometry versus culture

GERPAC Congress highlights

Impedance flow cytometry is a quick and easy method for estimating the numbers and viability of bacteria in faecal microbiota samples, according to Anne-Christine Joly (Saint Antoine Hospital, Paris).

Pharmaceutical preparation units need rapid, economical methods for testing of faecal microbiota transplant material. It is possible to estimate the total microbial load and viability using flow cytometry but this is costly and complex to implement. The technique requires fluorescent labelling of cells. Impedance flow cytometry (IFC) counts and analyses cells by measuring variations in electrical current as they pass individually through an electromagnetic field. This study aimed to compare IFC with the current reference method (culture) to determine its usefulness for routine use.

Twenty stool samples, 10 from healthy donors and 10 from patients, were analysed by both methods. The results showed that there was no statistical difference between the two counting methods. The researchers concluded that the high degree of concordance between the results suggested IFC would be a robust method for estimating total bacterial concentration and viability. IFC has the advantage of not needing specific [fluorescent] markers. However, it cannot identify bacterial species, noted Mme Joly.

Sintes R et al. Evaluating microbial viability differently: impedance cytometry versus culture. Short communication. GERPAC Congress 2025

Photo: Anne-Christine Joly.  Photo – courtesy of GERPAC