Modified enrichment-serology procedure for detection of salmonellae in soy products

Abstract

A modified enrichment-serology (MES) procedure was used to reduce the time necessary for salmonella analysis. Naturally contaminated samples of soy products were preenriched in 1% proteose peptone for 6 h at 37°C followed by inoculation into tetrathionate broth for 18 h at 37°C. Two drops of the tetrathionate sample were inoculated into M broth. After incubation at 37°C for 6 h, 0.85 ml of the mixture was formolized, and 0.1 ml of polyvalent H antiserum was added. After incubation in water bath at 50°C for 1 h, the appearance of a typical floccular flagellar precipitate was observed in tubes positive for salmonellae. Over 3,000 samples were subjected to standard biochemical and serological procedures, and the results were compared with those of the MES method with a 96.7% correlation. Eleven of the samples (0.3%) were false-negative with the MES procedure, and 3% were false-negative with the U.S. Food and Drug Administration Bacteriological Analytical Manual procedure. The 3% negative samples by this latter procedure were subsequently found to be positive by the MES procedure. The MES procedure reduced the time required for salmonella analysis from 4 days to 32 h.

Rapid Cultural Methods for Detection of Salmonella in Feeds and Feed Ingredients

“…Research efforts to channel selective enrichment cultures away from the sequential plating and biochemical screening steps to more rapid diagnostic tests, including enrichment serology (34), immunofluorescence (35), enzymelinked immunosorbent assay (26) and lysine-iron-cystineneutral red broth (5.15), have met with limited success. Recent work clearly showed that method brevity through incubation of preenrichment cultures for short (4 to 6 h) periods of time is not feasible (6).…”

“…Novobiocin concentrations of 5 to 80 t-Lg/ml have been used with limited success to increase the selectivity of liquid (18,22,34) and solid (19,23,27) media through inhibition of competitive flora, notably Proteus and Citrobacter spp. In the present study, addition of novobiocin (40 t-Lg1 ml) to SC and TBG failed to markedly increase sensitivity of the standard and 6-h standard methods, but apparently compensated for the low selectivity of SC 35 and TBG 35 in direct enrichment (Fig.…”

Development of a 24 h screen to detect viable salmonellas in faeces

“…impedcnce/conductance (Smith ef al. 1989), fluorescent antibody (Kodrigucs and Kroll 1990), enrichment scrology (Surdy andHaas 1981: 1Iumbcrt cf al. 1990), enzyme immunoassay (Araj and Chugh 1987;Lambiri et al 1990; van Pouckc 1990), latex agglutination (Hadfield rf ul.…”