Abstract
The sterility of trypticase soy broth (TSB) that was frozen and thawed in disposable plastic syringes and infused via syringe pump was studied to determine whether ambient air or personnel-transferred contaminants compromised the sterility of the solution. Samples of TSB (10, 20, 30 mL) were prepared aseptically in syringes of three different brands - 150 samples for each volume (50 for each manufacturer). The syringes were placed in zip-lock bags, stored for 24 hours at -15 to -20°C, and thawed for three hours. Both positive and negative controls were used. For the test samples, infusion sets were connected to the syringes under aseptic conditions, and the solution was infused via syringe pump in ambient air into polyvinyl chloride minibags before incubation. The remaining samples were prepared in the same manner as the test solutions except that they were intentionally challenged with Bacillus subtilis introduced distal to the plunger. All samples were inspected visually for turbidity after a 14-day incubation period. There was no growth in any of the test infusion samples or in samples that were intentionally contaminated. The negative controls showed no growth; all of the positive controls showed growth. The sterility of solutions frozen in disposable plastic syringes does not appear to be compromised by touch contamination of the plunger shaft or by airborne microorganisms settling on the infusion system.