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

Abstract

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.

Distribution of Methylomonas methanica and Methylosinus trichosporium in Cleveland Harbor as Determined by an Indirect Fluorescent Antibody-Membrane Filter Technique

“…The fluorescent antibody (FA) staining technique provides a means of examining specific microorganisms taken directly from their natural habitat and has been used for this purpose by many investigators (1,9,(12)(13)(14). The objective of this study was to develop an indirect FA staining technique which would permit the autecological study of Methylomonas methanica and Methylosinus trichosporium and to demonstrate the utility of the technique by determining the distribution of M. methanica and M. trichosporium in Cleveland Harbor.…”

Rapid detection of salmonellas in raw meats using a fluorescent antibody‐microcolony technique

“…However, the sensitivity and rapidity of the FA method make it highly desirable and much has been done to try to improve the method to widen the use of this approach. Filtering suspensions on Nuclepore filters (Early & Patterson 1982), the introduction of 4 h preenrichment phase to effectively reduce background fluorescence by diluting food materials or centrifugation steps to increase cell numbers (Thomason 1981;Ibrahim & Fleet 1985) and several semi-automated systems (Barrel & Paton 1982;Thomason et al 1975;Munson et al 1976) have all been described. Thomason (1981) also described the introduction of a procedure for growing microcolonies to aid detection by FA.…”

Hyperspectral Microscope Imaging Methods to Classify Gram-Positive and Gram-Negative Foodborne Pathogenic Bacteria

“…Current detection methods for foodborne pathogens include ISO method 6579 (ISO, 2002), direct fluorescence antibody detection (Munson et al, 1976), immunodetection such as enzyme-linked immunosorbant assay (ELISA) (Tian et al, 1996), and polymerase chain reaction (PCR) (Correa et al, 2006). However, all these methods are limited for practical use due to time-consuming processes, cumbersome results, and sensitivity concerns.…”