Reflection-optical multispectral imaging method for objective determination of burn depth.

We present a noninvasive imaging method for objective determination of the depth of burn wounds. The method is easy to use and enables even the nonspecialized physician to determine the burn depth at a very early time and to make available an objective documentation for quality management.

Evaluation of an automated fluorescent antibody procedure for detection of Salmonella in foods and feeds.

A prototype automated system using fluorescent antibody (FA) was evaluated for rapid detection of salmonellae in foods. Samples were enriched in selenite cystine and tetrathionate broths. After incubation, both were transferred into fresh selenite cystine for a 4-h "post-enrichment" to dilute possible background fluorescence from product. These cultures were then analyzed automatically, and results were compared with those obtained by the methods of the Association of Official Analytical Chemists (AOAC). Initially, 167 samples of milk powder, dried yeast, and imported frog legs were examined. The AOAC and automated FA methods correlated well with all samples but frog legs. Difficulty with the latter was caused by procedural and mechanical problems coupled with high numbers of competing microorganisms in post-enrichment cultures. Modification of procedure and partial redesign of equipment corrected these difficulties, and excellent correlation was obtained with another 116 frog leg samples. All 89 AOAC-confirmed positives were also detected by the automated FA method, and there were only 4% false FA positives. The system shows potential for screening products for salmonellae; however, all positives should be confirmed by manual biochemical and serological methods.

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.

Detection and growth of enteropathogenic Escherichia coli in soft ripened cheese.

The organism most frequently encountered during the 1971 outbreak of enteropathogenic Escherichia coli (EPEC) in soft ripened cheese was a strain that failed to ferment lactose broth within 48 h. Since existing methods for E. coli are dependent upon fermentation of this sugar, such strains can remain undetected, particularly when present in low numbers. Therefore a cultural testing procedure was developed to insure isolation of both lactose-positive and -negative strains. This method used GN broth, modified by substituting lactose and arabinose for glucose and D-mannitol, as an enrichment medium. MacConkey agar, used as a plating medium, was modified by substituting arabinose for half the lactose. The cultural procedure was used in conjunction with a fluorescent antibody method to screen cheese for the presence of presumptive enteropathogenic E. coli. Suspected isolates were subjected to further biochemical and serological testing and identified as members of specific serogroups. These methods were used for the analysis of over 2,000 wheels of cheese; over 10% of the samples tested were found to contain strains belonging to six different serogroups associated with diarrheal diseases. No attempt was made to confirm pathogenicity by in vivo tests. Enumeration of E. coli in cheese showed that numbers increased during storage. Cheese with less than 10 organisms/g initially increased to over 10-5 at room temperature and over 10-3 at 4 C within 10 days. With higher initial counts, levels up to 10-9 were found at 4 C. These studies showed that the high levels of E. coli encountered in these products cannot be used as a direct indicator of post-processing contamination.