Batch-swirl method for detoxification of isopropyl myristate used for sterility testing of oils and ointments: membrane selection.

A 1-hr batch-swirl method was developed for the preparation of isopropyl myristate to be used in the sterility testing of oils and ointments. The method is simpler and faster than that in USP XX. Flow rates of various membrane filters were tested. Cellulose acetate filters increased the filtration rate of oils and ointments and, thus, reduced the exposure time of possible microbial contaminants to the toxicity of isopropyl myristate.

Microbial ranking of porous packaging materials (exposure chamber method), ASTM method: collaborative study.

A collaborative study involving 11 laboratories was conducted to measure the microbial barrier effectiveness of porous medical packaging. Two randomly cut samples from each of 6 commercially available porous materials and one positive and one negative control were tested by one operator in each of 11 laboratories. Microbial barrier effectiveness was measured in terms of logarithm reduction value (LRV), which reflects the log10 microbial penetration of the material being tested. The logarithm of the final concentration is subtracted from that of the initial concentration to obtain the LRV. Thus the higher the LRV, the better the barrier. Repeatability standard deviations ranged from 6.42 to 16.40; reproducibility standard deviations ranged from 15.50 to 22.70. Materials B(53), C(50), D(CT), and E(45MF) differ significantly from the positive control. The microbial ranking of porous packaging materials (exposure chamber method), ASTM method, has been adopted First Action by AOAC INTERNATIONAL.

Method for maintaining viability of Clostridium perfringens in foods during shipment and storage: collaborative study.

A collaborative study was conducted in 12 laboratories to determine the effectiveness of a new method for maintaining vegetative cells of Clostridium perfringens in viable condition during storage and transport of food specimens to the laboratory. The collaborative results showed that treatment of brown gravy and roast beef samples with an equal amount by weight of sterile buffered glycerol-sodium chloride solution to give a final 10% glycerol concentration and storage with Dry Ice for 10 days at -56 degrees C resulted in plate counts of C. perfringens which were 2-4 log cycles higher with 2 different strains than counts with untreated specimens stored by the usual method at -20 degrees C. Plate counts obtained with the treated specimens stored with Dry Ice were less than 1 log cycle lower than counts made with identical specimens before freezing for storage and shipment to the collaborators. The results with treated specimens were also more uniform among the different laboratories. Because the new method for storage and shipment of food samples was so effective for maintaining viability of the organism, the official first action method for C. perfringens (46.B01) was changed to incorporate these procedures as part of the method.

Effects of temperature and relative humidity on biological indicators used for ethylene oxide sterilization.

A study was made to determine the effects of temperature and moisture on the D-value of a common biological indicator. Relative humidity (RH) was varied between 10 and 70% in increments of 10%, and temperature was varied between 30 and 70 degrees C in increments of 10 degrees C. Temperature was found to have a pronounced effect on the D-value. At 60% RH, the D-value varied from 15.0 min at 30 degrees C to 1.1 min at 70 degrees C. When RH was plotted against the average D-value at the various temperatures, the temperature curves at or above 50 degrees C were more erratic and the RH had a significant effect. The study showed that temperature and RH must be controlled if biological indicators are to be properly calibrated for use in ethylene oxide sterilization.

Comparison of bacterial recovery by Reuter centrifugal air sampler and slit-to-agar sampler.

Bacterial recovery by a portable Reuter centrifugal air sampler and a standard Mattson-Garvin slit-to-agar air sampler was compared in a series of experiments. Microbial air quality was monitored in seven typical laboratory locations. Tests showed that the Reuter centrifugal air sampler yielded significantly higher recoveries than did the slit-to-agar unit.