Centralization of vitamin-lipid blend production: validation of the alternative Bactec^® method for sterility testing

Context
Vitamin-Lipid Blend (VLB) are sterile preparations used for nutritional supplementation for premature newborns. The production of VLB syringes, previously carried out within patient care units, has recently been centralized within the Pharmaceutical Technology department. In this context, a microbiological control method using membrane filtration has been validated. This technique requires a prolonged incubation time, which is incompatible with the limited shelf life (7 days) of VLBs, making its practical application difficult.
The objective of this study is to validate the alternative Bactec^® method (automated blood culture system) for the microbiological testing of centrally produced VLBs, in order to optimize release times while ensuring compliance with regulatory requirements.

Method
Tests were conducted to validate the sterility, fertility, and applicability of the Bactec^® method in conformity with the requirements of the European Pharmacopoeia (EP) (2.6.1 Sterility & 5.1.6 Alternative Method). Other parameters were also tested: specificity, robustness, detection limits, and sensitivity.
The experiments were conducted using the six microbial strains specified by the EP (C. sporogenes, P. aeruginosa, S. aureus, A. brasiliensis, B. subtilis, and C. albicans) at 50 CFU and 10 CFU, with 3 repetitions performed by 3 different operators on 3 different days, including positive and negative controls for each test series.
The cultures were incubated in the automated system at 35 °C until the bottles tested positive.

Results
The results turned positive in a range from 11 to 83 hours, and 100% of the tested inoculant were detected. On average, cultures of bacterial strains turned positive in 15 hours, and those of C. albicans and A. brasiliensis respectively turned positive after 24 and 48 hours. Growth rates were equivalent between the VLB culture mediums and the positive controls. The negative controls showed no microbial contamination after 5 days of incubation. The identification of the microorganisms present in the culture mediums was consistent with the inoculated strains.
The robustness and detection limits of the method were tested by varying the inoculation volume (5 mL vs. 10 mL) and the quantity of contaminating microorganisms (10 CFU vs. 50 CFU), with no impact on the method’s performance, both in terms of detection rate and positivity period.

Discussion – Conclusions
The various parameters tested demonstrated the equivalence of the Bactec^® method according to the EP criteria. This method is a viable alternative to membrane filtration, with sensitivity and detection times suitable for daily use.

Mesh terms: pharmaceutical preparations, parenteral nutrition, microbiological techniques

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