The effect of refrigeration and mixing on detection of endotoxin in parenteral drugs using the Limulus Amebocyte Lysate (LAL) test.

Prior to testing for the presence of bacterial endotoxin, parenteral products are handled and stored in a variety of ways. Two incidents, detected by the U.S. Food and Drug Administration, revealed that differences in product handling and storage may have played a role in causing analytical discrepancies in the testing of identical samples. The testing procedure was the USP Bacterial Endotoxin test using Limulus Amebocyte Lysate (LAL) reagent. Consequently, an evaluation was made at the two principal factors that contributed to the suspected analytical anomaly. The factors were sample storage and the degree of agitation prior to sample analysis. Additional variables such as bacterial growth medium and adsorption potential of endotoxin by rubber stoppers were also evaluated. It was found that neither the medium employed to grow the E. coli endotoxin nor the storage temperature of the spiked solutions were problematic. However, it was shown that 20-40% of the spiked endotoxin was lost due to non-agitation of solution in vials in which the solution was in contact with the rubber stoppers. A suggested remedy for this problem is to store intact product containers in an upright position and to establish a uniform mixing procedure prior to endotoxin assay.

Survey of infant foods for Clostridium botulinum spores.

A total of 236 samples of infant foods, including honey, dry cereal, nonfat dry milk, evaporated milk, canned formula, and canned baby food, were collected in the New York City area and tested for the presence of Clostridium botulinum spores. Methods for recovery of spores were validated using foods spiked with 4 spores/mL or g. None of the products contained C. botulinum spores, indicating that their incidence in these commercial foods is not widespread. This limited study did not identify any food types that could be suspected of being involved in the transmission of infant botulism.

Fluorescent antibody method for the detection of Salmonella: development, evaluation, and collaborative study.

In preliminary studies, several commercial polyvalent fluorescent antibody (FA) preparations were evaluated for specificity and crossreactivity and an FA method was developed for the screening of Salmonella in products. Approximately 4000 product samples were tested by the FA method and the results were compared to those from the official final action AOAC method, 46.013-46.026. Only 4 FA false-negatives were found for a total of 619 confirmed positive Salmonella samples. The FA false-positive rate was 7%. The method was then subjected to a 2-phase collaborative study. In Phase I, 22 analysts tested 5 inoculated and 5 uninoculated samples of dried milk. In Phase II, 5 naturally contaminated and 5 presumably uncontaminated foods were analyzed. The study was designed to compare results from 11 analysts experienced in FA methodology with those from 11 analysts with little or no experience. Selenite cystine (SC) and tetrathionate (TT) broths were used for enrichment and both were inoculated into SC for post-enrichment. All 4 combinations (SC, TT, SC-SC, and TT-SC) were used with the FA method to determine the best technique. Results were compared to the analysis with TT and SC by the AOAC culture method. In all studies, FA analysis with SC-SC gave the highest correlation with the AOAC method. In a total of 200 samples, the experienced group found 125 AOAC positives and 127 FA positives; no FA false-negatives and only 2 false-positives were reported. The inexperienced group reported 9 FA false-negatives and 5 FA false-positives. All false-negatives occurred in only 3 of the inexperienced laboratories. These studies showed that enrichment and post-enrichment in SC gave the best FA results and that training in FA methodology is required for correlation with existing AOAC methodology. The FA method for the detection of Salmonella has been adopted as official first action.