Abstract:Enterococci were presented in all tested samples of raw cow milk (six samples) at the level 10 3 -10 5 CFU/ml, fresh cheeses (five samples) at the level 10 2 -10 6 CFU/g and semi-hard cheeses (five samples) at the level 10 3 -10 5 CFU/g.All 33 isolated enterococcus strains were screened for decarboxylase activity by usage differential growth medium and 20 of them possessed tyrosine decarboxylase activity. A collection of eight strains with the strongest decarboxylase activity were identified by species specific PCR as e. faecium (Z3, Z4, Br4 and 6/4D strains) and e. faecalis (Ž4, 3/3C and 4/1A strains). enterococcus spp. Z1 strain was not identified at the species level by used methods, but the genus was confirmed by PCR method. Their tyrosin decarboxylase activity was confirmed by TLC and detection of tdc gene. Z1, Z3 and Z4 strains showed also histidine decarboxylase activity on the differential growth medium with histidine, but this activity was evaluated by TLC as a false positive reaction of medium.
Tůma Š., Kučerová K., Plocková M. (2008): Isolation of anticlostridially active lactobacilli from semi-hard cheese. Czech J. Food Sci., 26: 324-332.The group of 7 strains of facultatively heterofermentative lactobacilli (FHL) of the non starter lactic acid bacteria (NSLAB) isolated from semi-hard cheeses using a well agar diffusion assay possessed a different level of inhibition activity against 16 different strains of Clostridium sp. belonging to the species Cl. butyricum, Cl. tyrobutyricum, Cl. beijerinckii, and Cl. sporogenes. Two selected strains with the production of partially indentified anticlostridially active inhibitory substances, lb. paracasei ST68 (producing hydrogen peroxide) and lb. paracasei 171R2 (producing bacteriocin and hydrogen peroxide), were tested for the inhibition activity against gas producing Cl. butyricum 10702 and Cl. tyrobutyricum 184 in cheese slurry. The effects of both strains were different in reducing the numbers of gas producing Cl. butyricum 10702 by > 3 log cycles and Cl. tyrobutyricum 184 by > 1 log cycles in cheese slurry during the tested storage periods of 24 days at 13°C. The Cl. tyrobutyricum strains isolated from spoiled cheese were identified by species-specific PCR for Cl. tyrobutyricum.
A collection of lactic acid bacteria (38 enterococcus and 41 Lactobacillus strains) was tested for the antilisterial activity against 15 Listeria spp. strains (two L. monocytogenes, one L. ivanovii and 12 L. innocua strains) using agar spot method. Out of all 79 bacteria only six enterococcus strains (1/3A, 3/3A, 6/4D, 6/1A, 1282 and EN3) exhibited antilisterial activity against almost all used indicator strains, when their live cells were tested. When their cell free neutralised supernatants (CFNS) were tested against four selected indicator strains (L. innocua Ln-03, Ln-06, Ln-10 and L. monocytogenes CCM5576) only two enterococcus spp. strains were active -e. faecalis 6/1A strain from raw cow milk of minor interest due to the activity of its CFNS only against L. innocua Ln-06 and thermolability of the compound and e. mundtii 1282 strain from goat raw milk with CFNS active against 13 Listeria spp. strains including L. monocytogenes. e. mundtii 1282 strain produced probably a bacteriocin, because it completely lost the activity after treatment CFNS with proteinase K.
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