Bioburden and theoretical sterility dose calculation for radiation sterilization of surgical cotton and bandages

The initial bioburden, count of colony forming unit (CFU) was determined on the locally manufactured non-sterilized surgical cotton and bandages. In all 489 tests were conducted on 163 cotton samples and 246 tests on 82 bandage samples. The surgical cotton showed an average of 198 microbes with a maxima of 287 and minima 94 whereas bandages showed an average of 179 microbes with a maxima of 268 and minima of 89. In the 20% samples subjected to identification no anaerobic microorganism was isolated while the aerobic microorganisms isolated were all bacilli. The sterilization dose (SD) for sterility assurance level (SAL) of 10(-6) was 2.23 Mrads and 2.21 Mrads, whereas the device verification dose (DVD) was 0.6 and 0.59 Mrads for cotton and bandages respectively as calculated by the method proposed by the Sterilization Standard Committee, Association of Advancement of Medical Instrumentation (AAMI).