Test for sterility using membrane filtration : validation of a new method

4 October 2018

A.Danckaert, J.Randrianary , F.Danicourt, A.Feutry, S.Granry, F.Monard, S.Richez, E.Janvier Centre Hospitalier de Calais, France


Test for sterility is necessary to check microbiological quality to prepare parenteral nutrition (NP)

For the qualification of the automated NP preparation and following the non-conformity of the technique used by the laboratory compared to the process described in the Pharmacopoeia, the methology for the test for sterility has been reviewed.


To validate the growth promotion test and the feasibility of the test for sterility according to the Pharmacopoeia.


First, the growth promotion test : the culture media are directely incubated with aerobic and anaerobic bacteria, contained in calibrated and frozen microbial balls according to the Pharmacopoeia : C. sporogenes, P. aeruginosa, S. aureus in 3 containers of Fluid thioglycollate medium (FTM 100ml) , A. brasiliensis, B. subtilis, C. albicans in 3 containers of Soya-bean casein digest medium (SCD 100 ml)

Secondly, we prepare 3 NP bags test of 200ml in a laminar flow hood, with a fixed composition and representative bag compared to the routine. Thereafter, we obtained 6 bags of 100 ml by splitting

Each micro-organism is introduced into a syringe and diluated with 10ml of one of bag test an. Then, the syringue is reinjected into the bag (≈30 UFC).

In a laminar flow hood, the contains of each bag is filtered thanks to a vacuum pump with a funnel. The membrane filter having a pore size 0.45 µm retain the micro-organims It’s taken with sterile clamp and introduced to the medium corresponding to the micro-organisms.

FTM is incubated at 30-35°C and SCD at 20-25°C. The microbial growth is determined by visual examination 3, 5 and 14 days after the beginning of incubation

Appropriate negative control is included for each medium

To validate the new method, the bacterial growth must be comparable to positif control


We observe the growth from the third day for FTM and from the fifth day for SCD medium. It’s comparable to the positif control for each container.


The method is validated with positif result for each micro-organisms. Before the sterility test was realized by the laboratory; it is now done by the pharmacy technician after the NP production. The vacuum pomp is easily decontaminable, has the advantage of saving space, and the filtration of 100ml is very fast.

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