Indicator organisms for safety and quality--uses and methods for detection: minireview.

Indicator organisms have been used for nearly a century to assess the microbiological status of water and foods. Beginning with their use in water sanitation programs, their applications have been extended over the years to other products, and they have become important components of the microbiological testing programs of both industry and regulatory agencies. Functionally, they may be viewed as safety or quality indicators. Safety indicators suggest the presence of conditions associated with increased risk of exposure to a pathogen. Quality indicators assess conditions of importance to product manufacture or consumer acceptability. This minireview summarizes the history, use, and analytical methods for the most commonly used indicator organisms, including the aerobic plate count, yeasts and molds, the coliform groups,

Comparison of assurance gold salmonella EIA, BAX for screening/Salmonella, and GENE-TRAK Salmonella DLP rapid assays for detection of Salmonella in alfalfa sprouts and sprout irrigation water.

The Assurance Gold Salmonella EIA, BAX for Screening/Salmonella, and GENE-TRAK Salmonella DLP rapid assays were compared with official cultural methods described in the Bacteriological Analytical Manual (BAM) for analysis of alfalfa sprouts and sprout irrigation water for the presence of Salmonella. The lower limits of detection of 4 serovars of Salmonella cells (S. tennessee, S. muenchen, S. mbandanka, and S. cubana) in pure culture were determined as approximately log10 2, 5, and 6 for the BAX, GENE-TRAK, and Gold EIA, respectively. Despite its low detection limit, the BAX did not perform as well as the other assays in analyzing contaminated sprouts and sprout irrigation water. For 4 different lots of sprouts and sprout irrigation water samples inoculated with the 4 serovars at low [1-2 colony forming units (CFU/g)] and high (68-180 CFU/g) levels, the BAX detected Salmonella in 58/64 (90.6%) of the samples, compared with 64/64 (100%) by the GENE-TRAK, Gold EIA, and BAM methods. Assay performance was also compared for analysis of naturally contaminated sprouts and sprout irrigation water with 3 lots of alfalfa sprouted seeds associated with different salmonellosis outbreaks. Positive assay results for the naturally contaminated samples were Gold EIA 41, GENE-TRAK 36, BAM 33, and BAX 13.

Fluorescent Antibodies Applied to Direct Epifluorescent Filter Technique for Microscopic Enumeration of Escherichia coli 0157:H7 in Milk and Juice.

In a modification of the direct epifluorescent filter technique (DEFT), direct fluorescent antibody staining was used for the rapid (<1 h), specific enumeration of foodbome Escherichia coli 0157:H7 by epifluorescence microscopy. Cell counts obtained by this method (Ab-DEFT) correlated well with DEFT counts obtained by acridine orange staining and with viable plate counts ranging from 108 to 101 cells per ml for pure cultures in buffer. Ab-DEFT also was effective for counting E. coli 0157:H7 cells inoculated into milk and juice; the sensitivity limit was about 103 for milk. The highly specific nature of the technique was demonstrated by enumeration of E. coli 0157:H7 cells in the presence of large numbers of indigenous spoilage microorganisms in milk. This is the first known demonstration of the combination of DEFT and antibody probe technology for the specific enumeration of a microbe directly in food without a growth or enrichment step.