The radiation resistance of ascospores and sclerotia of Pyronema domesticum.

The Food and Drug Administration has become aware of several instances where supposedly sterile medical surgical products made of Chinese cotton have been found to contain viable Pyronema domesticum. The aim of this research was to determine the gamma and electron beam radiation resistance values for the two dormant phases (ascospores and sclerotia) of P. domesticum. The resistance values were obtained by developing a standardized system to cultivate, purify, and harvest biological indicators containing sclerotia or ascospores. Ascospores were more resistant to radiation than sclerotia. The D(10) values for sclerotia were 0.79 and 1.09 kGy for strains 32030 and 14881, respectively. The resistance value for wild type ascospores was 2.83 kGy. The current standard for assuring radiation sterilization of medical devices is ISO 11137. This standard was developed to address the propensity for highly radiation-resistant organisms such as P. domesticum. Prior to the standard, biological indicators such as Bacillus pumilus, having a nominal D(10) value or 1.7 kGy, were used to determine the sterility of many medical devices.

New connection method for isolating and disinfecting intraluminal path during peritoneal dialysis solution-exchange procedures.

Microbiological data have been collected on the performance of a new method of isolating and disinfecting the intraluminal path at the connect/disconnect site of a peritoneal dialysis (PD)-exchange pathway. High-temperature moist-heat (HTMH) disinfection is accomplished by a new device that uses microwave energy to heat the solution contained in the pressure-tight inner lumen of PD connector pairs between the transfer-set connector-clamp and the bag-connector break-away seal. An 85 degrees C (S.D. = 2.4 degrees C, n = 10) rise in solution temperature is seen in 12 seconds, thus yielding temperatures under pressure well over 100 degrees C with starting temperatures of 25 degrees C. Connector pairs were prepared by inoculation of a solution suspension containing at least 10(6) colony-forming units (CFU) of a test micro-organism. Approximately 0.4 mL of solution was contained within the mated connector pair. Using standard D-value determination methods, data were obtained for surviving organisms versus five exposure times and a positive control to obtain a population reduction curve. Four micro-organisms (S. epidermidis, P. aeruginosa, C. albicans, and A. niger) recognized to be among the most prevalent or problematic in causing peritonitis were tested. After microwave heating, the treated solution was aseptically withdrawn from the connector pair using a needle and syringe, plated in growth media, and incubated. Population counts of CFUs after incubation were used to establish survival curves. Results showed a tenfold population reduction in less than 3 seconds for all organisms tested. A 30-second cycle time safely achieves a > 10(8) population-reduction for bacteria and yeast organisms, and a > 10(7) population reduction for fungi. One potential benefit of using this new intraluminal disinfection method is that it may help reduce peritonitis resulting from the even more problematic pathogens such as the gram-negative bacteria and fungal organisms.