Validation of the microbiological control of the parenteral nutrition bags by membrane filtration with the Equinox® pump by Millipore (steritest) and by direct seeding

Introduction

The sterility control of the binary, nominative and standardized parenteral nutrition bags, prepared in our unit, is currently carried out by direct seeding. The purpose is to validate, before implementation, membrane filtration method comparatively to direct seeding.

Methods

The trials were made according to European Pharmacopeia 9th Ed. : sterility tests, fertility tests on the culture media and applicability of the method with 3 operators. 18 bags of 200 ml with a representative composition, were seeded with 6 calibrated strains Bioball 30 UFC (Biomérieux) and then filtrated with the Steritest Equinox® pump (Merck - Millipore), on Thioglycolate and Trypticase Soy media. For direct seeding, 1 ml of every bag was seeded on 2 media: Brain-Heart Infusion Broth (BHIB) and Sabouraud dextrose agar slope (Biomérieux).

Results

The results of the sterility and fertility tests are conclusive for the membrane filtration method. Concerning direct seeding, Clostridium sporogenes has not grown on BHIB. Membrane filtration method allows the detection of the contamination of the 18 bags for a concentration of 0, 14 UFC/ml. The presence of the seeded germ was confirmed. Comparatively to membrane filtration, direct seeding allow the detection of only 2 contaminated bags on 18. For the nominative bags, the periods of growth (2 to 5 days) remain long comparatively to alternative methods.

Conclusion

This study allows us to validate the applicability of the membrane filtration for the parenteral nutrition bags, in our conditions. The superior sensibility of this method, against direct seeding, is brought out for the same primary level of contamination. Complementary studies are being prepared in order to determine the detection threshold of the direct seeding.