Bacterial contamination of automated MRI contrast injectors in clinical routine

Aim: To quantify the frequency of bacterial contamination of the injected contrast agent/saline solution by an automated contrast injection system, and to evaluate whether usage of a novel tube system can reduce it. Methods: For bacterial contamination quantification two identical automated piston pump MRI contrast injectors were used in combination with a standard tube system. 3-5 ml of the contrast agent/saline solution was collected from the system prior to its connection to the patients' venous cannula in 104 consecutive patients. To test, whether a novel tube system reduces contamination, a tube system with shielded screw connections was used with the same contrast injectors and contrast agent/saline samples were collected in further 101 patients. Specimens were microbiologically analyzed. Frequencies of contamination were compared using Fisher exact test. Results: With the standard tube system, bacterial contamination was observed in 5.8% (6 out of 104 specimens). With the novel tube system, contamination was observed in 2.0% (2 out of 101 specimens, p=0.280). Staphylococcus epidermidis was the most common germ (5 cases) followed by Micrococcus luteus (2 cases) and Oligella ureolytica (1 case). Conclusion: Bacterial contaminations of MRI contrast injectors occurred in a non-negligible frequency especially with S. epidermidis. A trend towards reduced bacterial contamination was seen when a novel tube system with shielded screw connections was used.