Pre-Sterilization Bacterial Contamination on Disposable Hypodermic Syringes: Necessary Information for the Rational Choice of Dose for Radiation Sterilization

The numbers and types of micro-organisms contaminating disposable plastic hypodermic syringes have been assessed prior to sterilization. A large number of syringes have been taken at random from the production lines of three independent manufacturers. The microbiological investigations were carried out in the laboratories maintained by each of these manufacturers for routine sterility testing, according to a standard protocol devised by the Research Committee of the UK Panel on Gamma and Electron Irradiation, which co-ordinated the investigation and analysed the results. Items produced by any one manufacturer were assessed for microbial contamination both in their own laboratories and in the laboratories of the other manufacturers. The level of false positive' results was determined independently for each laboratory by the testing of known sterile' items which had been subjected to the radiation sterilization process. Both the percentage of syringes initially sterile, and the average number of organisms per contaminated syringe differed among the three manufacturers. When corrected for differences between the assessments by the various laboratories, the ranges observed were 16-48% initially sterile, and 20-70 organisms per contaminated syringe. Of 964 syringes tested by all three laboratories, only one contained over 1000 aerobic organisms (1133). The most common organisms found on the 62 more heavily contaminated syringes (100-1000 organisms) were coagulase-negative Gram-positive cocci. Two manufacturers assessed contamination by anaerobic organisms; on 610 syringes, one contained 4275 organisms, three more had 100- 1000 organisms, but 488 (80%) were uncontaminated by anaerobes. The results are discussed in the context of the choice of radiation dose necessary for the sterilization of medical products manufactured under controlled hygienic conditions. (author)