Needleless injection devices use multiple-dose vials for the administration of local anesthetics to patients. There is a theoretic risk of iatrogenic infection associated with use of these devices.
This study used in vitro models to investigate the potential for transferring microbial pathogens among patients by using the Syrijet (Keystone Industries, Inc, Cherry Hill, NJ). Staphylococcus aureus and coagulase-negative staphylococci were used to determine whether patient skin flora could contaminate the instrument internal canal by postejection reverse flow and whether the staphylococci could survive on the ejection surface, in the internal canal, or in the anesthetic vial.
The ejection surface was contaminated by firing the device while it was in contact with a contaminated surface. Postejection reverse flow drew contaminants into the device, and increased with ejection volume. Reverse flow did not reach the multidose vial, and staphylococci did not grow in the commercial anesthetic solution typically administered with the device. Surface, but not internal, contamination could be removed by swabbing with disinfectant.
Although autoclaving is the only way to ensure sterilization of this device, frequent cleaning of the ejection surface during clinical use minimizes the risk of cross-patient bacterial transfer.