Microbiological Evaluation ofSuture Items Before Radiation Sterilization

Microbiological contamination levels ofsuture samples taken atvarious stages ofthemanufacturing processina new hygienically controlled plant were determined byemploying a membrane filturation technique. Bothraw material andmaterials handled manually intheproduction processwere tested toassess theeffect ofmanualhandling on theproduct contamination level. Evaluation of theefficacy ofcontamination control, however, was directed primarily tothe finished, packaged products, justprior totheprocessing withcobalt 60.The suturematerial fortesting was divided into twogroups,namely, wetanddry products, thewetbeing packaged inaspecial "tubing" fluid consisting mainly of isopropyl alcohol. Initial contamination results arereported as theaverage of values obtained on thetestdayandthepreceding 9consecutive production days. A totalof1,787suturesamplestested inthedrygroup showeddaily averagesvarying between 2.1and14.8contaminants per suture. The2,980 wet-packaged suture samples tested gavedaily averagesvarying from0.7to4.2 contaminants persuture. Thehighest values obtained foran individual suture were400forthedryand89forthewet.Identification studies ofthecontaminants revealed thatfungi predominated. Mostofthebacterial contaminants proved to bespore-forming rods. Microbiological control insuturemanufacturing plants isgenerally assessed bysterility testing ofproduction itemsthathavealready beensubjected totheradiation process. The radiation process itself maybecontrolled or monitored withtheaidofbiological indicators. Themostwidely usedbiological indicator for radiation sterilization isBacillus pumilus (1,8). Investigations directed tothedetermination oftheinactivation rates ofthedifferent types of