Szita G., B. Gyetvai, J. Szita, M. Gyenes, N. Solymos, L. Soos, A. Hajos, P. Toth, S. Bernath: Synthetic Culture Media Evaluated for Detection of Coliform Bacteria in Milk, Cheese and Egg Melange. Acta Vet. Brno 2008, 77: 143-147. Simple synthetic culture media of liquid and solid form (X broth and X agar) were tested for selective isolation of coliform bacteria. Selectivity is based on the ability of coliform bacteria to grow when the minimal medium contains simple inorganic substances as nitrogen and carbon supply. Selectivity of the media was tested by inoculation of pure cultures of different microbes belonging to the genera of Staphylococcus, Bacillus and Pseudomonas and the family Enterobacteriaceae and was found to be complete in this range. The comparative investigation of milk, camembert cheese and egg melange samples in the traditional and new media proved good applicability of X broth and X agar for an effective and selective detection of coliform bacteria. When testing pasteurized milk samples, X agar detected coliforms in significantly higher counts than violet red-bile-lactose agar.
Coliform, Escherichia coli, novel synthetic selective media, foodIn food microbiology qualitative and quantitative determination of indicator flora is a commonly used procedure which allows rapid conclusions concerning possible contamination of a product (Ingham and Schmidt 2000). Previously we developed an acetamide-containing minimal medium for the selective isolation of Pseudomonas aeruginosa (Szita et al. 1998). It was also demonstrated that Escherichia coli could be grown in a minimal medium containing only an organic carbon source such as glucose, a nitrogen source such as (NH 4 ) 2 SO 4 , and minerals (Jay 1996). A new simple selective and differentiating synthetic medium (X broth), which is easy to prepare, was developed in a liquid form for the selective cultivation of coliform bacteria from foodstuffs. This synthetic medium contains ammonium salt as a nitrogen source, lactose as a carbon source, and buffer salts but is free of inhibitors. The selectivity of the X broth proved essentially better than that of the standard brilliant green-bile-lactose (BBL) broth. The results of nationwide tests of coliform bacteria determination demonstrated that there was no difference in reproducibility, but the comparability was significantly better when the X broth was used. Applicability of the synthetic medium (X broth) for a detection of coliform bacteria was also tested with good results by nationwide round tests on quick-frozen tomato paprika samples (Szita et al. 2003).The purpose of this study was to test the applicability of the new synthetic medium (X broth) and its solid form (X agar) for the detection of coliform bacteria in milk, camembert cheese and egg melange samples.
A selective synthetic solid minimal medium (BS agar) was developed to detect antimicrobial drug-residues in foodstuffs using Bacillus subtilis indicator culture. This medium contains an ammonium salt as nitrogen source and either glucose or sodium pyruvate as carbon sources.Its selectivity is based on the fact that Bacillus subtilis is still able to grow if the minimal medium consists of simple inorganic substances as nitrogen sources, and glucose or pyruvate as carbon supply. Using these new synthetic media for microbiological assays assessing certain antimicrobials, the diameter of the inhibition zones were 1.4-4 times wider than on the Mueller-Hinton agar.The advantages of the BS agars are their standard compositions, the absence of inhibitors, the reproducible quality and the low costs.
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