Abstract:Složilová I., Purkrtová S., Kosová M., Mihulová M., Šviráková E., Demnerová K. (2014): Antilisterial activity of lactic acid bacteria against Listeria monocytogenes strains originating from different sources. Czech J. Food Sci., 32: 145-151.Eight individual bacteriocin-producing lactic acid bacteria (LAB) strains and three bacteriocin-non-producing cheese starter cultures were evaluated for their ability to inhibit the growth of six Listeria monocytogenes strains, originating from the guinea-pig lymph nodes, raw cow milk, and manufacturing dairy equipment. Results showed that either live cells or cell-free neutralised supernatant (CFNS) and/or heated CFNS of six individual LAB strains (Lcc. lactis subsp. lactis CCDM 416 and NIZO R5, Lbc. plantarum HV 11 and DC 1246, P. acidilactici HV 12, and Ent. mundtii CCM 1282) and one starter culture (DELVO-ADD ® 100-X DSF) were effective in the suppression of at least one listeria strain. Neither any individual LAB strain nor starter culture was antagonistic toward all studied L. monocytogenes strains, indicating diverse sensitivity/resistance among L. monocytogenes strains to antimicrobial compounds of LAB. The significant susceptibility of listerias isolated from raw milk and dairy equipment together with the strong antilisterial activity of DELVO-ADD ® 100-X DSF could be applied in dairy technology, where commonly used starter cultures could play both the biopreservative and fermentation role.

Němečková I., Solichová K., Roubal P., Uhrová B., Šviráková E. (2011) Totally 75 raw milk samples were analysed with the methods employing the media compared -MYPA, PEMBA, Brilliance TM Bacillus cereus agar, and HiCrome Bacillus agar. The reference method with MYPA seems to be the most suitable for dairy plants laboratories because there is only low risk of mistaken identity. However, the samples containing miscellaneous micro-flora should be heat-inactivated before plating. Both positive and negative strains (totally 132) were isolated. Twelve strains, which could cause problems in the evaluation of the plates, were selected and identified by phenotyping and by PCR methods for Bacillus sp., B. cereus, and B. licheniformis. The PCR methods differed in their selectivity within particular bacilli group, within genera Bacillus, and within raw milk microflora.

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.

Abstract:The work was aimed at the growth suppression of cultured listerias strains by cultured lactococci strains or commercial mesophilic cheese cultures during common cultivations in the model UHT milk system (0.5% w/w of milk fat content) at 30°C during 18 h aerobically. Milk was primarily fermented by lactococci at the level of 10 8 CFU/ml and secondarily contaminated by listerias at the level of 10 3 CFU/ml. The most intensive growth suppressions of both Listeria innocua (CCM 5884 or Ln-03) strains were caused by Lactococcus lactis subsp. lactis (LCC 416 or CHCC 2281) strains or DELVO-ADD ® 100-X DSF cheese culture; the listerias growth reductions was from the level of 10 3 CFU/ml to 10 0 CFU/ml. Obtained results should be applied to dairy industry provided that HACCP, GHP and GMP systems must be observed. Bacteria of Listeria genus attract an attention because of the health safety of final products, especially secondarily ripening cheeses, in the dairy industry of the Czech Republic and the European Union (EU). The majority of listerias species are harmless. L. monocytogenes (LM) species is pathogenic for human with 20% of death on listeriosis (Macela et al. 2006). L. ivanovii species is pathogenic just for sheep (Batt 2000). LM represents a facultative intracellular pathogen, which infects hosts by alimentary way (Schech 1983). Raw milk produced in milk farms represents a danger source of LM contamination as long as it is obtained during milking under GMP non-performance. In dairies raw milk is treated by heat with a guarantee LM inactivation. Final products can be secondarily contaminated by LM under conditions of sanitation regimes defaults or production control errors with the assistance of HACCP system. Listerias are able to reproduce at low storage temperatures and because of long incubation period of listeriosis it is difficult to prove whether a final product was contaminated at a producer or at a consumer only. For that reason naturally ways of listerias elimination are found. For example lactic acid bacteria can reduce or inhibit listerias and show rich biochemical activities. KeywordsThere are various products with antilisterial effect on the market of the Czech Republic and the EU. Listex TM P100 is a well-known and described commercial product that contains a virulent strictly lytic phage of P100 type, which shows a high specificity against LM (Carlton 2005).The aim of this work was to check a biochemical potential of lactococci for the reduction of listerias' growth in the model UHT milk system. Cultivation conditions of used strains. Lactococci and cheese cultures were cultivated in M17 broth with lactose (0.5% w/w) (LM17 broth) at 30°C for 18 h aerobically. Listerias were cultivated in BHI broth at 30°C for 18 h aerobically. All strains were also cultivated in UHT milk (0.5% w/w of milk fat content) with/ or without addition of yeast extract (YE) (0.5% w/w) at 30°C for 18 h aerobically. For work were used 1% (v/w) inocula. MATEriAlS And METHodS StrainsEstimation of lactococci and listerias...

Active packaging systems based on the application of packaging materials with incorporated and/or immobilized antimicrobial agents provides one of promising trends in food processing. The object of this work was to test the effect of polyethylene (LDPE) packaging film treated with lacquer containing 5% (w/w) Nisaplin^® on the growth of lactic acid bacteria, aerobic sporeforming bacteria, Bacillus cereus and on the changes of total count of bacteria in packaged meat products and processed cheese. Peaces of cheese in contact with nisin treated film were stored at 21°C for 0, 7, and 28 days. The obtained results confirmed significant inhibitory effect of such packaging system against aerobic sporeforming bacteria, when the decrease of above mentioned bacteria contamination up to four logarithmic cycles were determined. In contact with sliced salami the significant decrease of total bacteria as well as lactic acid bacteria counts were found. During storage of packaged salami for two weeks at 5°C the total bacteria count on the surface of product in contact with the package dropped by more than one logarithmic cycles, present lactic bacteria were inhibited by more than two logarithmic cycles.