Sterility and use patterns of multiple-dose vials

The viability of microorganisms in multiple-dose vials (MDVs) and the use and in-use contamination rate of MDVs were investigated. Serial tenfold dilutions of stationary cultures of Escherichia coli and Pseudomonas aeruginosa were injected into 30-ml MDVs containing bacteriostatic agents, and samples were removed at 1, 16, 24, and 48 hours, and at seven days to test for viable organisms. All opened MDVs were removed from each patient-care area and the pharmacy in a hospital and tested for microbial contamination using an aliquot-sampling method. One nursing unit was visited each day, in random order, until all opened MDVs from all units and the pharmacy were collected. The day following collection, all newly opened MDVs at each unit were marked inconspicuously and tallied. On the first, sixth, and thirteenth day after marking, all marked MDVs remaining on the unit were tallied. Bacteria were isolated from deliberately contaminated MDVs when inoculated with 1-100 colony-forming units/ml or greater when the sample was tested within one hour after contamination. Only one product was positive in 16 hours, and none was positive beyond that time. A total of 928 opened MDVs was collected from 31 nursing units and the pharmacy; none was positive for microbial contamination, indicating that the contamination rate was probably less than 4 per 1000. Lidocaine, insulin, diluents, and heparin constituted 57% of collected vials. The length of time that opened vials remained on a unit and the number of opened vials per unit varied considerably between units. The cost, feasibility, and effectiveness of control policies regarding use of MDVs should be weighed objectively against potential benefits.