The occurence of atypically high presterilization microbial counts (‘spikes’) on hypodermic products

Abstract The results of a series of investigations into the distributions of microbial contaminants on single-use hypodermic products prior to radiation sterilization are presented in this paper. For hypodermic needles it was possible to fit formal negative binomial distributions to the frequency of numbers of contaminants on high proportions of product items, and thus to identify counts which were atypically high (‘spikes’). The distributions of microorganisms on normal production syringes and on syringes suspected of having been exposed to greater than normal opportunities for contamination could not be defined by simple formal mathematical distributions. It was concluded that ‘spikes’ exist as one of the normal events associated with the microbiological contamination of mass-produced hypodermic products and thus have to be taken into account when designing protocols to establish doses of radiation sufficient to attain desired minimum levels of sterility assurance.