Salmonellae and the Fluorescent-Antibody Technique: A Current Evaluation1

Abstract

The increased microbiological surveillance of foods by government regulatory agencies and industry has shown that salmonellae are an important cause of food-borne disease. The significance of salmonellae in food-borne disease has made it mandatory for regulatory agencies as well as industry to develop a rapid, reliable, and reproducible method for the recovery of salmonellae in feeds and foods. Standard cultural procedures have become increasingly sensitive but not without a proportional increase in the time necessary for salmonellae detection and confirmation. This test may require from 5 to 7 days elapsed time with all of the implied disadvantages. One of the most promising areas of activity is the rapid microbiological-serological technique employing an improved fluorescent-antibody procedure. While much has been done by the medical technologist, the application of this technique is relatively new in food microbiology. The published data show the method to be highly promising and possibly even more sensitive than the standard cultural procedure. This technique is not without its inherent problems. Like all methods under investigation, there are differences in procedure, validity, and interpretation of the data. These are cited, with a description and critique of the work done, in order to give the reader an opportunity to evaluate the state of the art.

One-Day Fluorescent-Antibody Procedure for Detecting Salmonellae in Frozen and Dried Foods 1

“…It is impossible to say whether more rigorous treatment of these enrichment broths would have yielded additional cultural positives, but these data indicate that the FA procedure is more sensitive than the standard cultural procedure. This observation has also been made by other investigators (5,11). The absence of false-negatives was not only encouraging but fortuitous.…”

The Fluorescent Antibody Technique for the Detection of Salmonella in Routine Use

“…Thomason, Cherry & Edwards (1959) in work with human faeces and rectal swabs obtained very high numbers of false positive results in the FAT, which were almost certainly due to the use of direct faecal smears and poor specificity of the antisera used. Later work by Thomason, McWhorter & Sanders (1964) I n a review of the application of the fluorescent antibody technique to the detection of salmonellae in natural materials, Goepfert & Insalata (1969) suggest that the FAT is a more sensitive indicator for the presence of salmonellae than cultural methods, for which there is some evidence (Laramore & Moritz, 1969). I n our experience an occasional false positive FAT result has eventually been found t o be a false negative culture result, lending support to this finding.…”

New Methods for Microbiological Analysis of Food

“…Most often, for even greater sensitivity and selectivity, fluorscence is combined with immunological techniques. In 1969, Goepfert and lnsalata (65) were reviewing the use of fluorescent-antibody techniques in the rapid detection of salmonellae in foods and feeds. Clostridia were being identified by this procedure in 1970 (49).…”